Genetic background of development of hypertension and novel antipertensive drugs.

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The present works, using kininogen-deficient rats (Brown Norway-Katholiek (BN-Ka) rats), revealed that renal kallikrein act as a flood gate for excess sodium or sodium retention in the body and the reduced excretion of renal kallikrein plays a critical role in the early stage of the development of hypertension.I.A role of renal kallikrein-kinin system for sodium excretion1. Comparing with normal BN-Kitasato (Ki) rats, deficient BN-Ka rats were sensitive to NaCl and 2% NaCl in diet developed hypertension, by excretion of less urine volume and urinary sodium than normal BN-Kr rats.2. A non-pressor dose of angiotensin II to deficient BN-Ka rats developed hypertension by accumulating sodium in cells through aldosterone release.3. Kinin generated showed natriuresis through B_2 receptor localized on the luminal side of the tubular cells, as shown by increased natriuresis by ebelactone B,which selectively inhibited carboxypeptidase Y-like exopeptidase in urine.II.A role of renal kallikrein-kinin system in the development of hypertension1. Spontaneously hypertensive rats (SHR) excrete less urinary kallikrein during the development of hypertension than Wistar Kyoto rats (WKY).2. Oxytocin induced natriuresis in anesthetized rats and excreted renal kallikrein. The kallikrein level in kidney of SHR was not different from that in WKY,but the kallikrein excretion by oxytocin were much lower, suggesting that SHR showed difficulty in secretion of renal kallikrein.3. The blood pressure reached a plateau in DOCA-salt hypertension of uninephrectomized deficient BN-Ka rats 2 weeks after the onset of the treatment.4. Renal kallikrein releasers, such as oxytocin, and urine kininase inhibitors, such as ebelactone B,may be novel anti-hypertensive drugs.