In 1964 he moved to Columbia University in New York where, as assistant professor of physiology, he established a laboratory to study the regulation of cardiac contraction. While in New York he described the mechanism by which calcium controls the interactions of the cardiac contractile proteins, and began his studies on the role of the calcium pump of the sarcoplasmic reticulum membranes in regulating the calcium fluxes that relax the heart. In 1967 he demonstrated that calcium uptake by the cardiac sarcoplasmic reticulum was sufficient both in quantity and rate to account for relaxation of the intact heart.
Dr. Katz returned to the University of Chicago in 1967 to become associate professor of medicine and physiology, and in 1969 moved to New York to become the first Philip J. and Harriet L. Goodhart Professor of Medicine (Cardiology) at the Mount Sinai School of Medicine. In 1972 he pointed out that ischemic contracture (the "stone heart") could be explained by the formation of rigor bonds when the contractile proteins are depleted of ATP. It was in his laboratory in New York that phospholamban, a protein kinase A substrate that mediates cyclic AMP control of the cardiac sarcoplasmic reticulum calcium pump, was discovered and characterized (the name phospholamban was provided by his wife). In 1975 he was awarded a Humboldt Prize by the West German government for a year's study in Heidelberg where he characterized the bidirectional fluxes of calcium across the sarcoplasmic reticulum membrane.
In 1977, following his return to the United States, he moved to the University of Connecticut School of Medicine to become the first chief of cardiology. Shortly thereafter, in an editorial written with Prof. H. Reuter of Switzerland, Dr. Katz pointed out the toxic consequences of an excessive rise in cytosolic calcium, which helped Cardiologists to appreciate the potential benefits of calcium channel blocking drugs then being introduced for clinical use in the United States. In 1978, his group demonstrated that stimulation by phospholamban phosphorylation is due to increased calcium-sensitivity of the calcium pump of the cardiac sarcoplasmic reticulum. Dr. Katz' group, in describing the reaction mechanism of this calcium pump, highlighted the importance of attenuation of an allosteric effect of ATP to stimulate calcium transport as a potential cause for relaxation abnormalities in the ischemic and failing heart. With his clinical colleagues, he provided evidence that pathological hypertrophy is associated with slowed left ventricular filling in hypertensive patients, whereas physiological hypertrophy in athletes is accompanied by normal, or even accelerated filling. This work provided a clinical extension of observations from Dr. Katz' earlier collaboration that showed different effects of physiological and pathological hypertrophy on calcium transport by rat cardiac sarcoplasmic reticulum. In the 1980s, Dr. Katz' research group shifted its emphasis to the role of lipids in altering membrane structure and function, and to the molecular structure and states of the calcium release channel of cardiac and smooth muscle.
In the 1990s. Dr. Katz' efforts shifted to studies of heart failure that linked clinical Cardiology to the basic sciences. He predicted that inotropic agents would be detrimental in patients with heart failure and that long-term administration of b-adrenergic blockers could benefit these patients. In 1990 he postulated that the beneficial effects of converting enzyme inhibitors might reflect an antiproliferative effect, and suggested that a “cardiomyopathy’ induced by hemodynamic overload contributes to the poor prognosis in patients with heart failure.
Following his retirement in 1998 he became Visiting Professor of Medicine and Physiology at Dartmouth Medical School where he teaches in several basic science and clinical. In 2008 he was appointed Visiting Professor if Medicine at Harvard Medical School where he lectures on heart failure in the core curriculum for second year medical students. In retirement he has also returned to an old interest in medical history.
Dr. Katz has been a member of many Academic Societies including the American Physiological Society, American Society for Pharmacology and Experimental Therapeutics, American Chemical Society, American Society for Biological Chemists and Molecular Biology and Biophysical Society. He is or was a Fellow of both the American College of Physicians and the American College of Cardiology, and served the latter as Governor for Connecticut. He was elected to the American Society for Clinical Investigation and was a member of the Editorial Board of the Journal of Clinical Investigation. He was also a member of the Association of American Physicians, American Association of University Cardiologists and the Association of Professors of Cardiology. He has served on several NIH committees, Study Sections, and Board of Scientific Counselors to the Division of Intramural Research at the NHLBI.
Dr. Katz has served the American Heart Association on the Executive Committee of the Basic Science Council and has been a member of the Council on Circulation since 1975, and a Fellow of the Council on Clinical Cardiology since 1989. He was Vice President for Councils and Chairman of the Council Affairs Committee of the AHA and a member of its Board of Directors, Administrative Cabinet, Science Advisory Committee, Medical Advisory Committee to the Pharmaceutical Roundtable, Task Force on Intercouncil Cooperation, Science Promotion and Education Working Group, and Task Force on Strategies to Increase Federal Research Funding. He has served on the Boards and/or Research Committees of the New York, Chicago and Illinois, and Connecticut Heart Associations. He was President of the Greater Hartford Chapter of the AHA where he established a Summer Student Research Program. He served on the Board of Directors and was Chair of the Scientific Board of the Stanley J. Sarnoff Endowment for Cardiovascular Science Inc.
Dr. Katz was the first elected Editor of The Journal of Molecular and Cellular Cardiology, the official journal of the International Society for Heart Research; he is also past President of the American Section of this Society. He was one of the first Cardiologists to enter China on an official visit in 1973, and served as Adviser to the Chinese Academy of Medical Sciences. He was Coordinator of Problem Area 3, Myocardial Metabolism, of the NIH-sponsored US-USSR Collaboration in Cardiovascular Research, and served on the Council on Cardiac Metabolism of the International Society and Federation of Cardiology.
Dr. Katz has published over 400 articles and chapters, and edited or co-edited more than 15 books. His single-authored text Physiology of the Heart is now in its 5th edition, and two editions of another book, Heart Failure: Pathophysiology, Molecular Biology, Clinical Management, have been published.
Dr. Katz received an honorary Doctorate of Medicine from the Carol Davila University, Bucharest, Romania in 1991. In 1995 the American Heart Association renamed its young investigator award for basic research the Louis N. and Arnold M. Katz Prize. Other Honors include a Moseley Travelling Fellowship from Harvard University in 1960 and a Humboldt-Preis from the Alexander von Humboldt Foundation, Bonn, W Germany in 1975. He was awarded the Research Achievement Award of the American Heart Association in 1989, the Peter Harris Distinguished Scientist Award of the International Society for Heart Research in 2004, the Lifetime Achievement Award of the Heart Failure Society of America in 2007, and the Medal of Merit of the International Academy of Cardiovascular Sciences in 2011. He has received several teaching awards including the Twenty-First Annual Charles N. Loeser Award for Outstanding Teaching of Basic Biomedical Sciences at the University of Connecticut, and was Elected keynote speaker at the “Student Clinician’s Ceremony by the Dartmouth Medical School Class of 2012.
Dr. Katz has been married since 1959 to Phyllis C. Beck; they have 4 children.