Distinguished Conversations: Barry M. Brenner



Raymond C. Harris, MD


Barry M. Brenner, MD

Dr. Harris: Dr. Brenner, how did you end up becoming a nephrologist?

My early life is a study of a bright boy, self-motivated and driven to advance by studying 15 hours per day, 6 or 7 days a week. This “deep work,” a form of intense, undistracted, and undisturbed study, is something I have engaged in throughout my life. Still, any success that flowed to me was because of the many people who gave me encouragement and boosts along the way.

In my youth, I was very intrigued by the natural sciences. When I was a young teenager, I already had a microscope and was looking at pond water and identifying all the different unicellular organisms moving through the field. This filled me with great delight. I did lots of chemistry experiments at home, and my parents gave me as gifts pure compounds and glassware; the latter I broke repeatedly. I also burned myself and made some explosions that stained the ceilings.

I attended Long Island University in Brooklyn, which gave me a scholarship. I came from a poor family where no one had been educated. My greatest advantage in growing up is that I was disadvantaged in terms of our modest family background and little external guidance regarding career development.

The person who helped me the most was a man named J. Robert Oppenheimer, who was head of the Manhattan Project, responsible for making the atomic bomb. He was a brilliant atomic physicist, who, although not known to me personally, intrigued me greatly with his story and spurred me to read extensively about atomic physics and his contributions to this evolving field.

When Oppenheimer graduated from Princeton, he wrote in the class yearbook under his photo, “undergraduate school—3 years,” and when I went to college I was driven to do better. By that I mean I graduated with honors in 32 months, with many of my course credits at the graduate level. So I beat him by a few months, which was my target, and I think this said something about my drive and ambition at the time.

“I was enamored by the research process”

I interviewed at several medical schools, but it was the University of Pittsburgh that most interested me. There I was interviewed by Harold Segal, a young assistant professor of biochemistry. At the end of a lengthy discussion about anti-matter and fundamental atomic physics, he said, “You will get a letter of acceptance later this week, and if you come here, I want you to work in my laboratory.”

When I started medical school at Pitt in September 1958, I also started in Segal’s laboratory. He had identified a new enzyme—a 5'-nucleotidase—and since Pitt was renowned for enzymology because Maud Menten, of Michaelis–Menten fame, had been on the faculty, Segal assigned me the task of working out the Michaelis–Menten kinetics for this new enzyme, which I did. We published the paper on the results in the Journal of Biological Chemistry a year later.

I was enamored by the research process. The scientific method to me was the Holy Grail.

I continued to work in research while going to medical school. At that time, 50% of the freshman class at the end of the year stayed over the summer to do bench research. The school provided funds for 2 months of summer research and half the class was involved—something I think is unheard of today.

The second year of medical school involved the study of pathology. Segal contacted the chairman of that department, Frank Dixon, the father of immune complex–mediated diseases, and like Segal, he urged me to work in his lab. “Work with me during the day in my lab, but you still have to be responsible for the slide sets and take the exams along with your class,” he said. I worked with him for 6 months and also did very well on the exams.

Thus Segal and Dixon redesigned the curriculum to fit me rather than slot me in as just another student. It served me extremely well. These were opportunities that I don’t think are offered to young people today, and I think that’s a tragedy.

Dr. Harris: Yes, I think that you’re exactly right. We need to be open to opportunities within or outside the curriculum for those who are creative and driven.

When I did my medical residency at Albert Einstein in New York, I also was blessed with a unique opportunity. Instead of having morning report for your residency to discuss the cases that came in the night before, we had what were called “morning prayers,” where each of the 30 residents in rotation was responsible for giving a talk on a scholarly topic of their choice. It had to be scientifically oriented and you were expected to bring to the session the person on campus most knowledgeable about the topic you were presenting. Department Chair Irving London presided over the session.

One day I gave a talk on a PNAS paper by George Porter and Isidore Edelman on the mechanism of induction of sodium current by aldosterone in toad urinary bladder. They showed that it was a DNA-dependent RNA synthesis step that took 90 minutes to unfold before the sodium current increased, and they could block it with an inhibitor of RNA synthesis. I drew all the figures on the blackboard because in those days there were no funds for us to make photocopies or slides. As an expert, I invited Robert Davis. He showed up with somebody I didn’t know.

I presented the material over the course of 45 minutes. Davis led the discussion and the person he brought with him also asked me some questions. When the session was over I felt good about it and left to supervise the care of patients and my interns. At lunch, Davis came back with this person I didn’t know…it turned out to be Robert Berliner, director of kidney research at NIH.

“Three to four uninterrupted years of laboratory experience”

Although I had already been accepted for fellowship training with Alex Leaf, Frank Epstein, Arnold Relman, and William Schwartz, Berliner said, “Those are programs that will dilute your energy because you will have clinical responsibilities. Come to NIH and we will give you 3 or 4 uninterrupted years of laboratory experience.” I joined his lab because I was intrigued with the delicacy of the micropuncture technique, with the micro-analytical skills that needed to be applied—like the intrigue of a watchmaker for his craft.

At NIH, I worked with a young woman, Julia Troy, who was leading the micropuncture technical team. Within a month of my joining the lab, Berliner came to me and said he had been invited to Stanford to be the discussant at a clinicopathological conference. He asked me to look over the case protocol they had sent him, and after I had done so, I told him, “I think I’ve seen this case before.” I didn’t remember where but I went home that night and scoured my unbound issues of the New England Journal of Medicine that I had meticulously saved. There, about a year earlier, was the protocol of the same patient with medullary cystic disease. I showed the article to Berliner and said, “All you need to do is talk about the concentrating mechanism and how it’s not working well when there are cysts in the medulla,” which is what he did at the Stanford conference. For the next 6 months, every time he saw me he asked, “Did I ever thank you for helping me with that protocol?” I had entered his inner sanctum.

Then I had the good fortune of doing the micropuncture experiment that disproved the geometry hypothesis. That hypothesis came out of Gertz’s laboratory in Germany and then Floyd Rector and Donald Seldin (University of Texas Southwestern Medical School, Dallas) picked it up. The hypothesis stated that the more the tubule was dilated, the greater the absorption rate. So the square of the radius of the proximal tubule was proportional to the isotonic fluid flux across the tubule. The experiments were done by dilating the proximal tubule by producing intratubular obstruction with an oil block, similar to how blocking the ureter would raise intratubular pressure. What they didn’t do, and I did, was I realized that unless I had a very long oil block below where I was sampling the fluid, there was retrograde flow from more distal portions of the nephron into the pipette. They did not estimate the tubule fluid-to-plasma concentration ratio and the volume per minute collected because if they did and multiplied the two, which gives you the single nephron GFR, it would come to about 300 nL/min, which if multiplied by 30,000 nephrons per kidney would be nearly10 mL/min GFR in a rat—an impossible result. The rat doesn’t have much more than 10 mL of blood volume!

So by putting in these very long oil blocks, there was no retrograde backleak, and the estimated single nephron GFR was approximately 30 nL/min, the normal physiologic value for the rat. Under these circumstances where the tubule was dilated, the reabsorption rate did not increase, so it was insensitive to the square of the radius of the tubule. On the other hand, when I used short oil blocks, I obtained the artificially high estimates reported by the Dallas group.

I tell you this story because then something that never happens did happen. Berliner told me to write up the results for Journal of Clinical Investigation. I said I was happy to do so but also wanted to share the results with Rector and Seldin before we published. He thought that unnecessary but I thought it was essential. So I paid my airfare to Dallas and showed the draft manuscript to them. Rector looked at the data and immediately said to me, “You’re right and we’re wrong.”

A year later, I was back in Dallas meeting again with Rector and Seldin. Fred Wright and I failed to obtain evidence showing that volume expansion with saline led to the release of a natriuretic third factor, whereas the Dallas group had already published several papers and had a half-dozen in press about this so-called third factor. (Third factor meaning not GFR, not aldosterone, but something else.) We brought them unknown plasma samples from some dogs that we volume expanded, some that we didn’t, and they got only half right—and, more important, half wrong! Their studies suggesting a third factor were the result of an artifact in the shrinking droplet technique that they employed.

These two examples of sharing data prior to publication are, I believe, uncommon practices in today’s scientific community, but in my early career development, these interchanges proved very beneficial.

Dr. Harris: Right, and taking advantage of the opportunities and having mentors who both helped you and allowed you to take advantage of those opportunities.

Actually, our work on the square of the radius geometry hypothesis was done in 1967, the year of the first ASN meeting. And do you know the three state-of-the-art lecture titles at the first meeting in Los Angeles? One was called “Renal Physiology” and was given by Berliner. Another was called “Dialysis,” and the third, “Transplantation.”

Berliner presented my data and talked about Barry Brenner 5 or 6 times in his lecture, so that at the end of the first ASN meeting and the end of my first year as a fellow, everybody in nephrology knew my name. Talk about pure good fortune.

I had to pay to go to the meeting because Berliner would only send one person and it was a more senior person. My salary as a fellow at NIH (I was not part of the military) paid me $2000 a year. Yet my wife Jane, a schoolteacher, said, “Barry, you’re going to do this,” and paid for the trip.

I listened to Berliner give his talk, then on my own I flew up to San Francisco at the height of Haight-Ashbury in the 1960s. I wanted to see what it was all about. So I took a walk across the Golden Gate Bridge. The fog came in, and I could actually touch it. I looked toward the city and it was most beautiful thing. I said to Jane when I got home, “I don’t know where we’re going to live after we finish here, but it’s going to be San Francisco. I won’t open any envelope with a job offer unless the return address is San Francisco.” And of course it was.

“I took an offer because I could grow a clinical service slowly while doing research”

I received invitations from Larry Earley, head of renal at UCSF, and from Marvin Sleisenger, chief of medicine at the VA. I took the latter offer because I wanted so much to protect my personal research time as I did not want to inherit a big clinical service. In this way I could grow it slowly at my own pace while doing research.

Julie Troy and I both moved to San Francisco in 1969. While at NIH, we had built a device that allowed for real-time measurement of pressures in the renal microcirculation. The NIH basically made a long-term loan of this servo-null transducer system because we were now working at another government institution.

We were using the device to measure pressures in peritubular capillaries and for experiments looking at peritubular capillary control of proximal reabsorption when at a meeting in Munich, I was talking to Klaus Thurau, who said, “We don’t have any interest in this but you might, Barry. We have some rats that are showing cherry red spots on the surface of the kidney. We assume they are arteriovenous malformations.” I knew instantly that these were surface glomeruli.

I asked him to send me a dozen rats so I could take a closer look. A week or so later, I got a call from Lufthansa cargo at San Francisco airport telling me a box of rats had arrived. I went down to the airport to fetch the rats and sign whatever documents were needed, and counted not 12 but 11 rats, whereas the manifest said 12. So one rat escaped through a small hole. After that, I would never let my family fly Lufthansa, for fear the sole escapee might be eating through the cables that connect the wings to the body of the plane.

We quickly confirmed that the red spots on the surface were indeed glomeruli, and the pulse contours were highly refined.

We sent half the rats for breeding to the people who took care of animals at the VA hospital. We labeled them “Munich Wistar Rats” in honor of the city in which they were discovered, the way people would at that time name hemoglobins—for the city where a particular mutation in a hemoglobin molecule was identified. The name stuck—they are still called Munich Wistar Rats.

So we recorded the glomerular capillary pressures, and from there we were able to do the biophysics of the glomerular circuit. In collaboration with Bill Deen and Channing Robertson from the Chemical Engineering Department at Stanford, we were able to do the quantitative assessment of the ultrafiltration coefficient and a lot of the regulatory steps.

“A finding that led us in the direction of understanding progression of renal disease”

We prepared several papers on the dynamics of glomerular ultrafiltration, and in the eighth paper, which was intended to examine the effect on the dynamics of the reduction in renal mass surgically created, we were struck by the increase in single nephron GFR and the rise in glomerular capillary pressure that drove that rise in GFR. It dawned on me, “Well, maybe this rise in GFR as an adaptation to reduced renal mass is not a good thing because over time, the remnant kidney deteriorates and capillaries, like blood vessels in general, don’t tolerate high pressure.” We have no trouble comprehending how arterioles are damaged by hypertension, so why would there not be damage in capillaries if hypertension is imposed at that level? That led us in the direction of understanding progression of renal disease and the interruption of disease progression by lowering of those glomerular pressures. First we lowered glomerular pressures by dietary protein restriction and this proved to be beneficial long-term. Then we needed a pill—because who is going to give up their beefsteak?

The pill had to be something other than a pill that only lowered systemic blood pressure because up to that time, every antihypertensive drug was a vasodilator, and although they lowered systemic pressure, they opened up the afferent arteriole and the glomerular pressure did not decline. Therefore there was no renal benefit to be expected. But we had been working on the effect of angiotensin II, which we showed constricted the efferent arteriole, not the afferent, and believed that if there was something that could relax the efferent arteriole, that would be a way to lower intraglomerular pressure selectively. And then came the ACE inhibitors captopril and enalopril, both of which indeed lowered intraglomerular pressure dramatically and thereby minimized progressive glomerular injury.

“Bringing molecular biology to the renal division at Brigham”

In 1976, I along with a number of our San Francisco VA team accepted positions at Brigham and Women’s Hospital in Boston. An early recruit to our new program, Steve Hebert, was at that time perfusing isolated tubules. I also recruited Matthias Hediger, who, with Ernie Wright, had used expression cloning to identify the sodium-glucose cotransporter-1 and show that mutation of the transporter resulted in glucose-galactose malabsorption. His work was beautiful—I admired it and I got him to come to Brigham. I also recruited another molecular biologist, Jonathan Lytton, so I had these two young scientists doing pure molecular biology in our renal division.

Hebert was so taken with their work that he took an intramural sabbatical. He stopped perfusing tubules and learned how to do the molecular biology. His first success, with a fellow named Kevin Ho, was to clone renal outer medullary potassium channel (ROMK1). He then cloned the thiazide-sensitive NaCl cotransporter, and then NKCC2, the thick ascending limb transporter, and then the calcium-sensing receptor, all in a period of 3 years. Hebert went on to Yale, was elected to the National Academy of Sciences and, sadly, died suddenly at the age of 61. Hediger went off to Zurich, and then to Bern, where he directs an institute of molecular research. Jonathan Lytton went home to Calgary, Canada, where he is now chairman of the department of biochemistry. It was a very special time—a Camelot for us at Brigham, with these people adding an enormous dimension to the research.

So you now have a sense of how I got into nephrology and how my early career was bolstered by very good fortune, being given very important problems to work on (e.g., the existing hypothesis for explaining proximal absorption), exploiting those unique rats with surface glomeruli, doing the pure basic science drill on glomerular ultrafiltration, but then leap-frogging it into a clinical context and showing how the glomerular hypertension plays a role in the progression of kidney disease.

In the latter sense, what we did was take the various renal diseases, all of which progress, and say there is a final common pathway that underlies the progression of all of them. It doesn’t mean that this is the sole mechanism. It doesn’t mean that everything is explained by this hypothesis, but it went a long way toward unifying disparate entities into something that made a more coherent story. For me, it was one of the major milestones of my career.

Dr. Harris: I think your career is a paradigm of someone who has been interested in basic science and has always been willing and able to translate it into clinically relevant issues.

Well, for me, it was following a single thread. The nephron GFR is driven more by plasma flow than by hydraulic pressure. It’s a low pressure system, whereas when we made the first measurements and I looked in Robert Pitts’ book, Physiology of the Kidney and Body Fluids, the estimate of glomerular pressure was assumed to be 90% of the systemic pressure, not 40% as we had demonstrated. When you think about it, how could a capillary endure such pressure? But the single thread took those pressure measurements from low to higher values when nephron reduction occurred, whether by disease or by surgical reduction of renal mass. Now I am preoccupied with more of the same thread. What if you are born with fewer nephrons? Isn’t that like renal reduction by surgery and doesn’t that constitute a potential risk for progression of renal disease?

As you know, it does. But I have been unsuccessful in 30 years at getting physicians to use the simple surrogate for low nephron number, namely low birth weight. Question number one: What was the endowment of nephrons a patient started with? Instead, everyone starts at the same place—it is wrongfully assumed that everyone starts out with 1 million nephrons in each kidney. It’s the number every student remembers. Not a million plus or minus 30%, which is the reality.

Dr. Harris: You’re right. What I think we should be doing is getting a better birth history, but also finding better ways to image and actually count glomeruli. I think that’s the next frontier.

Yes, and to make that a clinically feasible assessment in toddlers and young people as a baseline. Anyway, I’ve been frustrated with my inability to convince our renal colleagues that these steps must be taken. But I have reason to be encouraged. At Giuseppe Remuzzi’s invitation, I gave a plenary lecture on nephron endowment at the last ISN meeting in Cape Town in March 2015. The audience seemed impressed. I am pleased that a symposium on the theme of this lecture will be held under Remuzzi’s leadership in Bergamo, Italy, in April 2016.

Dr. Harris: So I think that your work is not done.

Well, it’s what keeps me on the younger side of my 78 years. It keeps me going. I remain deeply immersed in the issues that fascinate me, and I continue to devote myself to my favorite indoor hobby, deep work.

One final thing. I would like to express my unbounded gratitude and love to my wife, Jane, our children, Rob and Jen, and our grandchildren, Sam, Max, Elliott, and Abigail. I also thank all the fellows who taught me so much. I especially thank Julia Troy, the most able technical assistant the micropuncture field has ever known. When I bound all the articles she and I wrote together over the years into a book, I inscribed in the front cover, “To Julia Troy. With you, the voyage has been wonderful. Without you, I would never have left the shore.”