00:00:00 You are about to see an interview with Dr. Ronald Estabrook, conducted by Professor Frances

00:00:27 Scott of the Department of Chemistry at the Rochester Institute of Technology.

00:00:33 Ronald Estabrook received his B.S. in biology in 1950 at Rensselaer Polytechnic Institute.

00:00:40 He then did a doctorate in biochemistry at the University of Rochester in Rochester,

00:00:45 New York, working in the general area of mitochondrial function under Dr. Elmer Stotz.

00:00:51 Dr. Estabrook's thesis dealt with studies on the cytochromes of heart muscle extract.

00:00:57 He moved as a postdoctoral fellow to the University of Pennsylvania School of Medicine, and there

00:01:02 he worked under the direction of Dr. Britton Chance.

00:01:06 In 1968, he moved to his present position as professor of biochemistry and chairman

00:01:12 of the Department of Biochemistry at the University of Texas Health Science Center in Dallas.

00:01:18 Shortly after his arrival, he was awarded a personal chair in biochemistry called the

00:01:23 Virginia Lazenby O'Hara Professorship of Biochemistry.

00:01:28 His laboratory in Dallas over the past 14 years has been one of the world's foremost

00:01:33 in the area of cytochrome P450 structure, function, and chemistry.

00:01:41 Ron, the cytochrome P450 system has played a key role in the metabolism of foreign compounds,

00:01:53 xenobiotics, compounds that can cause cancer and so on.

00:01:58 And you have played a seminal role in the study of that system, particularly in Philadelphia

00:02:05 and, of course, then with your own fine research group back in Dallas.

00:02:10 Would you like to tell us a little bit about the Philadelphia story as far as cytochrome P450 is concerned?

00:02:16 Yes, that's a very interesting and, to me, a very rewarding period in my own scientific career

00:02:26 and one which I think can illustrate the many different turns that one can take

00:02:35 in terms of developing a program of research.

00:02:40 The period of 1950s, which is when this story began, was one of great excitement

00:02:49 in terms of understanding the mechanism of oxygen utilization in various tissues.

00:02:57 And primary emphasis was placed on mitochondria, in particular because the recognition of ATP synthesis

00:03:07 and all of the factors that influence this was still in its infancy, less than 10 years old.

00:03:17 There was, concomitant with the understanding of the mitochondrial electron transport system,

00:03:26 the beginnings of an understanding of what was called cyanide insensitive respiration.

00:03:32 It was known that the respiratory chain of the mitochondria was sensitive to inhibition by agents such as cyanide.

00:03:41 But there were, in some tissues, the ability of respiration to occur in the presence of cyanide.

00:03:49 It's interesting, as one reflects back, that during that period there were three different groups,

00:03:56 very active and, frankly, unrelated and not really communicating with one another.

00:04:04 Were they aware they were working on different aspects?

00:04:07 Not, to my knowledge, aware at all. These three groups were the following.

00:04:11 There was a very active group at the Worcester Foundation concerned with the transformation of various steroids,

00:04:18 in particular the breakdown by the adrenal cortex of cholesterol to the various metabolically active steroid hormones.

00:04:27 And who was the leader in that?

00:04:29 The leader would be, Lou Engel was one, Oscar Hector was another,

00:04:35 Alex Zaffaroni was very intimately involved in that group.

00:04:38 There were a very powerful series of investigators. That was one group.

00:04:47 The second group was operative at the National Institute of what is now heart and lung and blood diseases.

00:04:56 This was a group headed by B.B. Brody, Steve Brody.

00:05:01 One of, again, the most powerful scientific groups, but concerned, in this instance,

00:05:08 with toxicology and the degradative breakdown of various drugs.

00:05:14 Julie Axelrod was one of the participants in this group.

00:05:18 Sid Udenfriend, Jim Gillette, it was...

00:05:23 Were these largely biochemists? Was this a biochemical approach?

00:05:26 Those were largely pharmacologists, interestingly.

00:05:28 So we have, at the Worcester Foundation in Massachusetts, mainly endocrinologists,

00:05:33 concerned with steroid metabolism.

00:05:35 We have at the National Institute of Health, mainly pharmacologists, concerned with drug metabolism.

00:05:42 And a third group, which was at the University of Wisconsin, was Jim and Betty Miller principally,

00:05:48 concerned with the oxidative transformation and conversion of a number of compounds

00:05:55 that were then recognized to form cancer, or to be cancer-causing, carcinogenic compounds.

00:06:03 These were also pharmacologists rather than biochemists?

00:06:07 These were oncologists.

00:06:08 They were in the Department of Oncology at the McCardell Institute of Cancer Research at the University of Wisconsin.

00:06:14 So here we have these three groups operative in the 50s,

00:06:18 all recognizing that there was associated with many cells, in particular the endoplasmic reticulum...

00:06:25 Of the liver.

00:06:26 Of the liver, of the adrenal, of steroidogenic organs,

00:06:31 an enzyme system that required oxygen for the oxidative transformation of the chemicals,

00:06:38 electrons in the form of reduced pyridine nucleotide,

00:06:42 and resulted in an oxidative degradation or alteration of the chemical system.

00:06:51 The other facet of this problem, which took place, again, were two more factors.

00:06:59 Howard Mason at the University of Oregon, Osamu Hayashi in Japan,

00:07:05 were at that time doing studies with oxygen-18

00:07:10 and recognized that there were certain oxidative reactions which occurred called oxygenases,

00:07:16 which incorporated oxygen-18 into organic molecules.

00:07:21 These were called either mixed-function oxidation reactions,

00:07:25 mono-oxygenase reactions, or dioxygenase,

00:07:29 depending upon whether one atom or two atoms of a molecule of oxygen, atmospheric oxygen,

00:07:36 were incorporated into the product.

00:07:39 So there were the chemical studies. These were chemists that were doing O-18 studies.

00:07:45 Then there were the biochemists, and in particular, the one that sticks most in my mind

00:07:53 were the group of which I was a part in Philadelphia,

00:07:58 working in Britton Chance's laboratory,

00:08:01 where we had the opportunity, through the genius of Britt Chance,

00:08:08 in the manner in which he developed instrumentation

00:08:11 that would permit the recording and monitoring of spectral transition of hemoproteins

00:08:17 during the course of cellular oxidative reactions.

00:08:21 Was that a quantum leap in design of UV instrumentation?

00:08:24 Absolutely.

00:08:25 It was UV instrumentation?

00:08:26 No, it was visible, principally.

00:08:28 And the idea is, up to that time, these were too messy.

00:08:32 I mean, they were cloudy solutions.

00:08:34 The turbidity problem made it insurmountable.

00:08:37 And he solved that?

00:08:38 Yes, by the method of different spectrophotometry.

00:08:42 And, of course, using his knowledge of the amplifier systems

00:08:47 that he gained from his work on radar,

00:08:50 and also the associated development of photosensitive cells,

00:08:55 which were able to detect small changes in light transmission.

00:09:03 Britt Chance, at that time, had with him some spectacular people.

00:09:09 He was truly a man that I consider the brightest man

00:09:15 that I've ever had the opportunity to meet or to work with.

00:09:19 Are we talking about, say, 54, 55, in terms of history?

00:09:22 This is about the mid-1950s.

00:09:25 There were, at that time, in the laboratory, working on mitochondria.

00:09:30 All the work at that time was concerned with mitochondrial respiration.

00:09:34 A man named G.R. Williams, Ron Williams,

00:09:36 who is currently at the University of Toronto,

00:09:40 chairman of the Department of Biochemistry.

00:09:43 They were investigating what is known as metabolic regulation

00:09:49 or respiratory control of mitochondria during the associated formation of ATP.

00:09:57 As part of Ron's interest, a man named A.N. Pappenheimer,

00:10:02 now on Harvard University faculty,

00:10:05 was working at that time on diphtheria toxin

00:10:09 and had the hypothesis that somehow this was related

00:10:13 to succinate dehydrogenase of the mitochondria.

00:10:16 In other words, the toxicity induced by the diphtheria toxin

00:10:19 was a metabolic toxicity.

00:10:21 Absolutely.

00:10:23 The chance in his generosity,

00:10:27 we always had tremendous flow of individuals coming through the lab,

00:10:31 and Pappenheimer had contacted Chance,

00:10:35 came down and did a series of experiments

00:10:38 looking at the midgut of the cecropia, the silkworm of all sorts,

00:10:43 to see where diphtheria toxin might be inhibiting

00:10:47 mitochondrial oxidative metabolism.

00:10:50 Was there any reason that he chose the silkworm for this?

00:10:53 I honestly don't know.

00:10:55 I presume it was because of the sensitivity.

00:10:58 Now, Ron Williams was assigned the responsibility of working with Pappenheimer.

00:11:04 We each were given this job when visitors came to the lab

00:11:08 of working along with them and sort of helping them on the instrumentation.

00:11:12 Ron was a very methodical and also a very intuitive chemist.

00:11:19 And yes, he did the experiments he was supposed to do,

00:11:22 but he always used to do one or two more.

00:11:25 And one of them was part of our routine

00:11:28 in doing spectral analysis of turbid samples

00:11:31 was to look for unique carbon monoxide binding pigments.

00:11:35 And Ron, in the presence of a chemical reductant, sodium dithionite,

00:11:40 using this messy midgut preparation of the silkworm, cecropia,

00:11:46 added carbon monoxide and for the first time, to my knowledge,

00:11:50 saw the appearance of a very strong absorbance band

00:11:54 with a maximum at 415 nanometers in the blue part of the spectrum.

00:12:01 This, to my knowledge, was the first time that anyone had ever seen this hemoprotein.

00:12:06 May I ask you...

00:12:07 He didn't know what it was.

00:12:08 For those of us who are not familiar,

00:12:09 why did one normally use carbon monoxide atmospheres

00:12:13 to look for that inhibition?

00:12:15 Because was it derived from Warburg?

00:12:17 How far back did that kind of biochemical technique go?

00:12:21 Oh, this goes back to the early days of Hoppe-Seiler, actually,

00:12:25 in terms of hemoglobin.

00:12:27 Oh, they used carbon monoxide as a ligand routinely in hemoprotein studies.

00:12:31 Absolutely.

00:12:32 There were, you know, there were three cyanide,

00:12:34 which react with the ferricheme protein.

00:12:36 Carbon monoxide react with the ferrous.

00:12:38 And the analogy of carbon monoxide and oxygen

00:12:41 made that always the interesting agent to look at.

00:12:43 These three simple ligands, cyanide, carbon monoxide, and oxygen,

00:12:48 biochemists were using as respiratory tools for a long time.

00:12:51 For a long time.

00:12:54 And so I didn't mean to interrupt you.

00:12:56 The carbon monoxide spectrum showed a nice band at 450.

00:12:59 Right. And they never published this, interestingly.

00:13:02 They...

00:13:05 That remained...

00:13:06 That was about 1954, 55.

00:13:10 That remained sort of as a unique, unexplained observation,

00:13:15 which wasn't unusual,

00:13:16 because we were getting all sorts of preparations

00:13:19 that people would bring into the lab.

00:13:21 In other words, they bring in their little bottles,

00:13:23 put it through your machines, get data,

00:13:25 and not quite know what to make of it very often.

00:13:27 That's correct. Many times.

00:13:28 There are still pigments that, in bacteria,

00:13:31 carbon monoxide binding pigments,

00:13:33 that, you know, could remain as lifetime work

00:13:38 for individuals that have not yet been fully identified

00:13:42 or characterized or pursued in any depth at all.

00:13:45 It was interesting, during that time in the lab,

00:13:48 there was a Japanese Ryosato, S-A-T-O,

00:13:52 from Osaka, who had been with Hugo Terrell

00:13:56 in Karolinska in Stockholm,

00:13:59 who was working at that time, actually with me,

00:14:04 on a cytochrome from a salt-tolerant bacteria,

00:14:08 Helobacter.

00:14:10 Interesting.

00:14:12 A human protein which also still remains

00:14:14 to be further characterized.

00:14:16 And Ryo was a smart man.

00:14:20 He was interested in mammalian cytochromes

00:14:22 and unique cytochromes,

00:14:24 and was aware of the cytochrome P450,

00:14:27 as it is now called.

00:14:29 And in fact, Sato named it cytochrome P450.

00:14:33 The P450 meaning that the absorbance band

00:14:37 of the carbon monoxide ligand of the reduced hemoprotein

00:14:41 was in the blue part of the spectrum of 450 nanometers.

00:14:45 Now, Sato did not work on P450 in Philadelphia.

00:14:51 He went back to Osaka,

00:14:53 had a student, Suneo Omura,

00:14:56 and as part of this student's dissertation,

00:14:59 he was to work on the CO binding pigment.

00:15:02 And this culminated in the early 1960s

00:15:06 in two papers in the Journal of Biological Chemistry,

00:15:10 which were the first chemical definition

00:15:13 that a cytochrome P450 was a hemoprotein,

00:15:17 had protoheme as its prosthetic group,

00:15:20 was very labile in terms of its sensitivity to detergents,

00:15:27 to agents that would perturb the membrane.

00:15:32 In other words, when anybody tried to isolate it,

00:15:34 they messed it up.

00:15:35 Absolutely.

00:15:36 Made it very difficult to study.

00:15:41 It was interesting that at about the mid-1950s,

00:15:45 when Ron Williams, working with Papenheimer,

00:15:50 made this initial observation,

00:15:52 Martin Klingenberg was a visiting post-doctorate fellow from Germany.

00:15:58 Klingenberg was looking for a problem,

00:16:01 and he was working on liver microsomes,

00:16:06 and part of his spectral analysis of liver microsomes

00:16:11 recognized that cytochrome P450 was an integral part.

00:16:15 And...

00:16:16 Excuse me now.

00:16:17 The other man had been doing it in the silkworm.

00:16:19 This man was doing it in rat microsomes.

00:16:22 That's correct.

00:16:23 Because in the manner of preparation...

00:16:25 Now, you have to remember,

00:16:26 the major emphasis in the lab was mitochondria.

00:16:28 One would take the liver of an animal,

00:16:31 homogenize it,

00:16:32 subject it to differential centrifugation,

00:16:35 isolate the mitochondria,

00:16:37 and the remaining supernatant

00:16:39 contained the microsomal fraction

00:16:41 from the endoplasmic reticulum

00:16:43 plus the soluble proteins.

00:16:45 So that was always left over.

00:16:47 Klingenberg took what was left over after the mitochondria,

00:16:51 subjected that to...

00:16:53 Same kind of study, right?

00:16:54 Right.

00:16:55 In order to get this bright red pellet of microsomes,

00:16:59 which we know contains cytochrome P450 today.

00:17:02 Now, my own involvement

00:17:05 was more on the side during this period.

00:17:10 I was aware of what was going on.

00:17:12 And your PhD had been in respiratory,

00:17:14 in the mitochondrial...

00:17:15 Mitochondrial cytochromes here at the University of Rochester

00:17:17 with Elmer Stotz.

00:17:19 And I was concerned really with the intricacies

00:17:22 of what was called the cytochrome BC1C,

00:17:27 part of a mitochondrial...

00:17:28 Complex, right?

00:17:29 Yeah.

00:17:30 Where antamycin was the inhibitor,

00:17:32 and I was working on that computer simulation and so forth.

00:17:37 At Pennsylvania, again, it's the spirit of the times,

00:17:42 there was an organization called the John Morgan Society.

00:17:46 Now, John Morgan was the founder

00:17:48 of the University of Pennsylvania Medical School

00:17:51 in the late 1700s.

00:17:57 This honorary medical society

00:18:00 was to bring together clinicians and basic scientists

00:18:03 on the staff of the University of Pennsylvania Medical School.

00:18:09 And it was at one of these meetings I met David Cooper.

00:18:12 David Cooper was a board-certified surgeon

00:18:15 in the Harrison Department of Surgical Research

00:18:18 who was very concerned with hypertension

00:18:21 and steroid transformation.

00:18:25 He was firmly convinced, as it was understood in that time,

00:18:29 that steroids from the adrenal

00:18:31 were somehow critically involved in hypertension.

00:18:35 And David, in his reading,

00:18:37 had read a paper of Ryan and Engel, they were at Harvard,

00:18:42 about the oxidative conversion of steroids,

00:18:46 in particular the 21-hydroxylation,

00:18:48 the 11-beta-hydroxylation.

00:18:50 And very simplistically, his concept was

00:18:52 that biosynthesis of steroids might be involved

00:18:55 in the evolution of hypertension in certain individuals.

00:18:58 Absolutely.

00:18:59 In the etology, right.

00:19:01 And so he became concerned and interested in knowing

00:19:05 how are steroids interconverted.

00:19:07 Now, you remember I told you that,

00:19:10 oh, perhaps half a dozen years earlier,

00:19:13 the Worcester Foundation had this powerful group

00:19:16 looking at steroid interconversions.

00:19:19 And we went back to that literature,

00:19:21 and in particular the key paper was one by Ryan and Engel

00:19:24 in the journal Biological Chemistry,

00:19:26 who recognized that the oxidative transformation

00:19:32 of some steroids

00:19:34 was sensitive to inhibition by carbon monoxide.

00:19:37 Well, I'd worked with mitochondria,

00:19:39 and I had been brought up more or less

00:19:41 in the lore of the Warburg School,

00:19:44 which Chance was very knowledgeable of.

00:19:48 And Dave Cooper approached me about this problem

00:19:54 and said, how does one measure carbon monoxide inhibition

00:19:58 of an oxygen-requiring reaction?

00:20:01 So he was interested in the chemistry,

00:20:03 and you had the access to the instrumentation

00:20:05 to look at the mechanism.

00:20:06 Absolutely.

00:20:07 So we came together,

00:20:09 and we started to look and see

00:20:11 what was the mechanism of carbon monoxide inhibition

00:20:14 of steroid transformation,

00:20:16 in particular the 21-hydroxylation of progesterone

00:20:20 by the microsomal fraction of the B-fadrenal cortex.

00:20:25 We went back and we repeated the experiments of Ryan and Engel,

00:20:29 and indeed they were right.

00:20:31 The reaction was carbon monoxide inhibited.

00:20:34 It was...

00:20:35 Now, when you say inhibited,

00:20:36 do you mean it stopped or all the products were formed?

00:20:39 No, it depended on the ratio of carbon monoxide to oxygen.

00:20:42 It was a competitive inhibition of carbon monoxide to oxygen.

00:20:45 And this was a kinetic inhibition?

00:20:47 It was a kinetic inhibition.

00:20:49 We then...

00:20:50 I was aware of the work of Otto Warburg,

00:20:56 and we then thought

00:20:58 if the reaction is carbon monoxide inhibited,

00:21:01 perhaps it's light reversible.

00:21:04 And so we set up the apparatus to photodissociate the system

00:21:09 and measure its photochemical action spectrum.

00:21:12 Key to this whole arrangement at that time

00:21:16 was a man named Otto Rosenthal.

00:21:18 Otto Rosenthal was a German biochemist

00:21:22 who had been in Berlin,

00:21:25 knowledgeable also of the Warburg technique,

00:21:28 was working very close with David Cooper

00:21:32 in the Harrison Department of Surgery,

00:21:34 and he was just a wealth of information.

00:21:40 In other words, he had the prior technique of Warburg,

00:21:43 and you had the chance...

00:21:45 I could look at the turbid samples.

00:21:48 He had the Warburg apparatus

00:21:51 in terms of measuring oxygen utilization,

00:21:54 the ability to poise the system

00:21:57 with various carbon monoxide-oxygen ratios.

00:22:00 All that we needed were a very powerful light source

00:22:05 and a source of monochromatic filters.

00:22:07 Now, would the principle be that you were going to quench the reaction

00:22:10 with carbon monoxide and build up some key species

00:22:14 and then pop the carbon monoxide off under light stimulation?

00:22:17 The principle of the Warburg photochemical action spectrum technique

00:22:21 is that the maximum reversal

00:22:24 of carbon monoxide inhibition by light

00:22:27 occurred at the wavelength

00:22:29 where maximum absorbance of the carbon monoxide derivative occurred.

00:22:34 This is what Warburg had used to identify

00:22:37 cytochrome oxidase of mitochondria

00:22:39 as the terminal oxygen-interacting species.

00:22:42 Now, we tried these abortive experiments

00:22:48 and it was apparent that we simply couldn't get enough light into the system.

00:22:52 We then went out,

00:22:57 and I can remember the great difficulties

00:23:00 in getting the money to get a xenon lamp

00:23:04 that would permit us to get enough light energy

00:23:08 in the presence of monochromatic filters

00:23:11 to do some photochemical action spectrum.

00:23:15 We used an old Warburg apparatus

00:23:17 that Otto Rosenthal had brought with him from Germany, from Berlin.

00:23:21 It was the second or third Warburg apparatus in the world.

00:23:24 It was so ancient.

00:23:26 We borrowed monochromatic filters from a man named Lionel Jaffe.

00:23:31 I remember him very well,

00:23:33 who was in the biology department

00:23:35 who was at that time looking at photosynthetic reactions

00:23:40 and had the filters in order to do the photo action spectrum for photosynthesis.

00:23:46 Then we got the xenon lamp using first a light microscope lamp,

00:23:51 but that didn't give us sufficient energy either

00:23:54 to really do the experiments well.

00:23:57 And sitting and doing these experiments

00:24:00 and seeing for the first time

00:24:02 that a radiation of the carbon monoxide-inhibited system

00:24:07 with light of 450 nanometers caused maximal reversal.

00:24:12 Now you didn't obviously know this before you started,

00:24:14 and what you did was you irradiated a series of wavelengths

00:24:17 to look at the efficiency of reversal.

00:24:19 Absolutely.

00:24:20 And lo and behold, smack in there was 450 responding.

00:24:23 Absolutely.

00:24:24 With my previous knowledge of the 450 work

00:24:31 that Klingenberg and Sato and G.R. Williams

00:24:35 and Papenheimer and Garfinkel had done,

00:24:39 when we saw maximal reversal was of 450 nanometers,

00:24:43 the first thing we did was to go over

00:24:45 and put these microsomes in a spectrophotometer,

00:24:48 and lo and behold, it was loaded with P450.

00:24:52 And so that was the first realization of the function of this enzyme.

00:24:57 That's right.

00:24:58 Now, that's a historic paper.

00:25:01 It changed all your lives more or less.

00:25:03 It certainly changed yours.

00:25:06 Again, Dave Cooper, in his manner, which was,

00:25:10 it's hard for me to explain,

00:25:12 he had an intuition as to where things were.

00:25:16 As soon as we recognized the key role of P450 in the adrenal system.

00:25:22 And it was still not called P450?

00:25:24 It was not called P450.

00:25:25 It was the carbon monoxide binding pigment of microsome.

00:25:32 He put together the work, and from his knowledge of pharmacology,

00:25:36 that there was a comparable enzyme system in the liver,

00:25:41 which was responsible for the metabolism

00:25:43 and oxidative breakdown of many drugs.

00:25:45 Now, that was Brody's group.

00:25:46 That was Brody's group.

00:25:48 So we immediately set up the assay

00:25:50 to look at the conversion of codeine to morphine,

00:25:53 an oxidative demethylation reaction.

00:25:55 Formaldehyde was easy to measure,

00:25:59 so we started out looking at that system.

00:26:02 Now, was your technique the same in the sense it was inhibition

00:26:05 of the key reaction mechanistically by carbon monoxide

00:26:08 and popping it off at a series of wavelengths

00:26:11 and seeing whether the wavelength that it popped off

00:26:13 had the maximum at the P450 point?

00:26:15 That's correct.

00:26:17 We did this with the codeine to morphine system in liver.

00:26:21 We did it with acid aniline hydroxylation.

00:26:24 In other words, all the stuff that Brody had published in the 50s,

00:26:26 you looked at it again.

00:26:27 Absolutely.

00:26:28 We looked at the analgesic aminopyrine,

00:26:33 which was also undergoing demethylation,

00:26:36 and every one of them had the same pattern,

00:26:39 that the maximal reversal of carbon monoxide inhibition

00:26:43 occurred when we irradiated the sample with 450 nanometer light.

00:26:48 Now, historically, that would be 62, 63, 64.

00:26:52 That's correct.

00:26:53 There was Estabro, Cooper, and Rosenthal in Philadelphia,

00:26:57 and Omura and Sata in Japan had put together suddenly

00:27:00 and said to the rest of the endocrinologists

00:27:02 and the people in McArdle and the people at the NIH and said,

00:27:05 Look, we seem to have identified the pigment and the enzyme system

00:27:10 that's involved in all of your businesses,

00:27:12 in the steroid area, in the drug area, and in the carcinogenesis area.

00:27:16 And so 64 was the beginning, in a sense, of an explosion of interest.

00:27:21 We started looking at phenobarbital effects on the liver microsomal system.

00:27:25 And we're still looking now for this tolerance bit.

00:27:27 Absolutely.

00:27:29 And we saw that P450 was very responsive.

00:27:33 In a matter of three or four days,

00:27:35 one could triple the content of P450 in liver,

00:27:39 the CO-binding pigment,

00:27:41 as a consequence of treating animals with a barbiturate.

00:27:46 Well, this was the answer to Remmer's whole hypothesis,

00:27:50 which he had predicted,

00:27:52 that there was an enzyme system which was built up,

00:27:55 which was responsible for drug tolerance.

00:27:57 In other words, it more efficiently scavenged the agent

00:28:00 so less of it was in the bloodstream and therefore there was less effect.

00:28:03 Absolutely.

00:28:04 It caused a more rapid clearance of the drug and transformation of it.

00:28:09 So that was exciting.

00:28:11 My own, in general terms, driving force

00:28:14 is to understand the system sufficiently

00:28:17 so that we have some mechanism of regulating and controlling it.

00:28:24 I originally started out as a biophysicist, biochemist.

00:28:30 Over the years, I'm becoming more and more converted

00:28:33 to the potential importance of the system

00:28:37 in terms of understanding cellular toxicity and carcinogenicity.

00:28:41 Is the environmental toxicology area, for example,

00:28:45 blossoming under this insight, the toxicity aspect?

00:28:49 If one goes...

00:28:51 The genius of man in terms of his chemical abilities is fantastic,

00:28:58 yet we seem to live in a sea of chemistry

00:29:03 for which we have no true biological understanding.

00:29:07 No.

00:29:08 In other words, we have a chemical environment

00:29:10 in the sense we've synthesized many of these for useful purposes

00:29:13 and now we're left with the recognition that they can be threats to us.

00:29:16 Absolutely.

00:29:17 Now, do you think many, in terms of our political setup,

00:29:20 do you think we overreact to that threat?

00:29:22 Yes.

00:29:23 I don't think that the scientific data is all in,

00:29:26 and I think that, in particular, yes, there's a risk,

00:29:31 but I think somebody is going to have to come up

00:29:33 with a balance of risk versus benefit.