TISSUE RENIN-ANGIOTENSIN SYSTEM - A SITE OF DRUG-ACTION

In this review, we present background material that provides partial s upport for a tissue renin-angiotensin system (RAS). Evidence for the e xistence of this system relied in part on the use of drugs, which has entailed using low doses or concentrations of angiotensin-converting e nzyme inhibitors, renin inhibitors, and angiotensin antagonists to blo ck the RAS in vascular beds and in isolated arteries or organs. Other evidence for a tissue RAS has depended upon measurements of the compon ents of the system, i.e. enzymes, substrates, and mRNAs for these prot eins. All of these components were first believed to be present in the heart and blood vessels; however, it is now known that renin in the c irculating blood derived from the kidney is used for the local synthes is of angiotensins. The main emphasis of the review is on the renal RA S because it is believed that the local RAS is most prominent in this organ. The renal RAS is probably involved in the long- rather than sho rt-term regulation of renal vascular resistance and maintenance of nor mal blood pressure through the regulation of sodium reabsorption.