Some frontiers in comparative studies of the renin-angiotensin system

A prospective survey on the comparative studies of the renin-angiotensin system (RAS) was made at the final session of the Japan-U.S. Cooperative Seminar, held on November 14--19, 1977, at Jichi Medical School, Tochigi-ken, Japan. Strategies and tactics of the research have been clarified. In morphological studies, the strategy is to clarify structure of the juxtaglomerular apparatus in representative species of vetebrate classes. In chemical studies, each component of the RAS must be established in each vertebrate class. Since we now know the existence of severel new angiotensins in vertebrates, their amino-acid sequences must be determined. They must be synthesized in sufficient purity. It is necessary to establish the international purity and assay criteria for synthetic angiotensins. In comparative studies on physiological aspects, the strategy is to establish the physiological roles of the RAS in vertebrate classes. Controls of blood pressure, of aldostrone secretion, of glomerular filtration rate and tubular transport, and of drinking and intestinal absorpiton are the candidates. Physiological roles of extrarenal renin as well as renal one are interesting. A renin-like substance in the corpuscles of Stannius in the teleosts has been identified preliminarily as hypocalcin. Many frontiers exist in these fields, and one can expect fruitful contributions to research of the cardiovascular disease in humans through comparative studies of the RAS.