The overall objective of this proposal is to define the mechanism of function and physiological role of tissue renin antiotensin systems. We will test the hypothesis that renin in various tissues functions in a compartmentalized way, and will evaluate the significance of tissue renin- angiotensin systems, particularly that in the vascular system, in the elevation of vascular tone in spontaneously hypertensive rats (SHR) and other animal models of essential hypertension. Preliminary results indicate that hypertension in SHR persists after bilateral nephrectomy, but infusion of a renin inhibitor in the nephrectomized SHR markedly lowers its blood pressure. This finding suggests he importance of extra renal tissue renin. Since it is the secreted angiotensin II (ANG II) which is important in regulating vascular functions rather than the amount of the stored renin or ANG II, we have developed a sensitive method to measure the rate of ANG II release from the Krebs-Ringer perfused vasculatures and kidney. New synthetic and immunological inhibitors of renin, angiotensin receptor and lipophilic converting enzyme inhibitors (ACEI) will be used. Pure rat renin and angiotensinogen will be produced from recombinant DNAs. Using these inhibitors of the renin-angiotensin system, we will address the questions as to whether tissue renin-angiotensin plays the major role in spontaneous hypertension. By using the Krebs-Ringer perfusion system, we will determine the mechanism and control of ANG II production from vasculature, kidney and other renin containing cells. The mechanism by which angiotensinogen gain access to tissue renin will be clarified. Specifically, possible presence of angiotensin receptor or transport system in renin containing cells will be looked for using recombinant angiotensinogen. Whether tissue renin works by an extracellular or intracellular mechanism will be investigated. Intracellular pathway of packaging of renin and ANG II will be studied. The hypothesis that renin packaging takes place by way of 6-phosphymannosyl phosphate binding protein and/or newly discovered microsomal sortase will be tested using enriched JG and other types of cells. These studies will clarify the role and mechanism of action of tissue renin which has been unclear to date and expected to contribute importantly to our understanding of the mechanism of renin dependent forms of essential hypertension.
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