1979 Volume 21 Issue 11 Pages 1251-1263
The effects of 1-Sar-8-lle-angiotensin II (analogue) on rabbits with acute (11 days after clipping) and chronic (50 days after clipping) two-kidney hypertension were studied, 50 pg or 100 pg bolus of analogue was hand-injected into an ear vein and changes of blood pressure (BP) were observed as a rule for 10 minutes. The rabbits with acute phase hypertension had significantly high peripheral plasma renin activity (PRA) compared to preconstriction values. But PRA returned to preconstriction levels in chronic phase. Seven of 23 rabbits with acute phase hypertension responded to first administration of analogues Only 1 of 23 rabbits with chronic phase hypertension had a high PRA value with marked elevated BP and hematocrit (Ht), and responded to analogue injection. This rabbit showed no elevation of blood pressure in acute phase, so, in this time analogue injection was not performed. In acute phase hypertension, at first administration of analogue, BP, PRA and Ht of the res-ponders, were, significantly higher than those of the non-responders. Five of 7 responders at first administration of analogue in acute phase hypertension had a sustained high blood pressure in chronic phase, but all 5 responders in acute phase became to non-responders at first administration of analogue in chronic phase. BP and PRA of this chronic phase were significantly lowerer than those of the acute phase. All non-responders in acute phase hypertension had also no response at first administration of analogue in chronic phase. There were no marked changes of BP, PRA and Ht in these two phases. Each of responders and non-responders in acute phase hypertension became same non-responders at first administration of analogue in chronic phase. There were almost same levels of BP, PRA and Ht in these two groups. After volume depletion, about 30 percent of nonresponders at first administration of analogue responded to analogue. However, it is possible that sodium depletion stimulates renin release which, in turn, participates in maintaining the BP at the same level that existed prior to depletion. In this experiment, even control rabbits showed a depressor effect by the administration of analogue after volume depletion. This suggests that there are many difficult problems in differentiating the normal homeostatic response from pathologic response after volume depletion. In conclusion, as the hypertension became chronic, purely renin dependent hypertension had been involved in non-renin mechanisms. Moreover, this involvement decreased the degree of BP levels from severe to mild, These results suggest that angiotensin plays an important role in the pathogenesis of acute and severe two-kidney hypertension. However, angiotensin appears not to be the solely main pathogenesic factor in the maintenance of elevated BP in chronic hypertension or in mild hyper-tension. In clinical use, the analogue administration does not seem to provide a greater degree of sensitivity in the detection of unilateral renovascular hypertension.
