Interview with Joel Hardman
We want to start out with you, Joel, and your early days. What brought you to Pharmacology?
With Steve Mayer, I worked on glycogen phosphorylase and its regulation by catecholamines and cocaine. Earl Sutherland’s work at the time made it a natural transition for me to work with him, as he had worked out the mechanism by which epinephrine and glucagon activate phosphorylase in the liver, including the discovery of cyclic AMP.
What was the environment of Vanderbilt at the time?
It was a much smaller institution, but the scientific environment was terrific. Sutherland had gathered around him a great team including Al Robison and Bill Butcher. About two years after I came, Al moved into the Pharmacology Department at Vanderbilt, and Bill took the Biochemistry chair at the University of Massachusetts Medical School in 1969. John Exton also was at Vanderbilt. He had come about a year before I did and was Rollo Park’s postdoc. Park’s lab was just across the hall from Sutherland’s lab.
The environment of the Physiology Department was very informal, but scientifically intense. There were two seminar series that provoked a lot of discussion and thought. Fridays at noon, there were student and postdoctoral research progress reports. The highlight of the week was on Wednesday at noon, when there was a seminar series where only the faculty spoke, but not about their research. They talked about recently published scientific papers in a format something like a journal club these days. The Wednesday noon seminars were held jointly with the Departments of Microbiology and Molecular Biology, which meant that people such as Victor Najjar, Oscar Touster, Sidney Colowick and Sidney Fleischer were in attendance along with the Physiology faculty which included in addition to Park and Sutherland, Janey Park, Howard Morgan, Robert Post, Tetsuro Kono and Ray Meng. Hearing these people dissect and critique papers was a real education in critical scientific thought.
How did your post-doctoral project and subsequent work with Sutherland develop?
The postdoctoral project that I undertook in Sutherland’s lab dealt with the possible existence of cyclic nucleotides other than cyclic AMP. Shortly before I went to Sutherland’s lab, a group led by Duane Price in the Urology Department at Columbia had published a paper about the identification of organophosphate compounds that were excreted in rat urine. Using what was then state-of-the-art technology -two-dimensional paper chromatography- urine samples extracted after P32 loading of the animals were shown to contain only two P32-containing compounds. One was cyclic AMP, which Bill Butcher has already shown to occur in urine, and the other was cyclic GMP.
Sutherland encouraged me to see if there was a phosphodiesterase that could break down cyclic nucleotides other than cyclic AMP and use it to develop an assay for them using a recycling system that generated inorganic phosphate in measurable amounts.. Bill Butcher had identified and partially purified a phosphodiesterase from myocardium that could break down cyclic AMP. I found that it had an even higher affinity for cyclic GMP and used it in a primitive assay for that nucleotide. We also found a phosphodiesterase activity in myocardium that was cyclic UMP-selective, but we didn’t follow it up after publishing a short paper in the JBC, and neither did anyone else to my knowledge.
Joe Beavo came to the Sutherland lab as a graduate student in 1965. He greatly extended our work on phosphodiesterase activities in many tissues and then did postdoctoral work on protein kinases with Ed Krebs. Beavo joined the faculty in Krebs’ Pharmacology Department in Seattle, returned to his early interest in phosphodiesterases, and went on to define much of the current state of knowledge about the large family of cyclic nucleotide phosphodiesterases. His work brought him membership in the National Academy of Sciences.
With Jim Davis, I began to look for cyclic GMP in biological materials in 1965, and we were limited to urine for a good while because of the low sensitivity of our assay. We confirmed the report of the Columbia investigators and found cyclic GMP in urine, a lot of it. I don’t know that anyone has ever figured out what the biological advantage is for an organism to excrete so much cyclic nucleotide in the urine.
We went on to study changes in amounts of cyclic GMP and cyclic AMP in the urine of rats in various hormonal states. We found that glucagon treatment led to significant increases in cyclic AMP but not cyclic GMP. In the urine of hyphophysectomized rats, cyclic GMP levels were substantially reduced but there was little or no change in cyclic AMP levels. When we treated the animals with a cocktail of anterior pituitary hormones, cyclic GMP levels were restored to normal with little or no change in cyclic AMP. We thought these findings were important, because they suggested that these two cyclic nucleotides could be independently regulated and most likely were made by different enzymes.
So I began to look for a guanylyl cyclase, found it in several tissues and characterized activities in lung in both the soluble and particulate fractions. At about the same time, Arnold White at the NIH and Guenter Schultz in Heidelberg also found the enzyme, as did Eiji Ishikawa, who was working in Sutherland’s lab. Ishikawa found very high activity in the particulate fraction of intestinal mucosa. Years later, David Garbers would show that this intestinal guanylyl cyclase is a target for heat-stable bacterial toxins.
Arthur Broadus, now a professor at Yale, was an MD/PhD student working in our lab and extended our work with cyclic nucleotides in rat urine to human urine and blood plasma, using a more sensitive version or our assay that Eiji Ishikawa had developed. In collaboration with Grant Liddle and some of his fellows in Medicine, Arthur did pioneering work on cyclic nucleotide kinetics in human extracellular fluids and the regulation of cyclic nucleotide levels in plasma and urine by hormones.
Later, Pavel Hamet came to our lab on leave from the University of Montreal and further extended the studies with human extracellular fluids and did some fundamental work on vascular cyclic nucleotide metabolism in cell-free system. He returned to our lab for brief periods each year for several years. Pavel is a professor at the University of Montreal and has had a strong research career spanning basic and clinical research.