[The depressor effect of antihypertensive factor from rat erythrocytes].

This study observed the depressor effects of erythrocyte antihypertensive factor (AHF) from spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats on SHR, renal hypertensive rats (RHR) and their control animals. Blood pressure (BP) tests were carried out in two parts. Chronic experiment: Six-month-old male rats weighing 200-300 g were divided into six groups: (1) Stroke prone SHR (SHRsp, n = 5); (2) WKY (n = 4); (3) RHR (n = 4); (4) Wistar (n = 4). The rats in each group were given intraperitoneal injections of AHF (10 mg/100 g BW) once. The rats in groups (5) and (6) were injected with normal saline as control. BP was measured just prior to injection and at 0.5, 1, 3, 6, 24 h and 24 h intervals thereafter. BP in SHRsp dropped (from 180.0 +/- 11.5 to 145.0 +/- 12.6, P less than 0.05). Within 24 h there was a further reduction, and the average value of the fall was 65 mmHg (P less than 0.01). BP remained significantly depressed for 4 days and did not recover until the seventh day. In contrast to the effect of this extract on SHR, the BP in WKY rats did not appear to be affected. Normal saline injected intraperitoneally did not lower BP in either SHRsp or WKY rats. BP in RHR rats showed a profound decrease within 3 h, with the average value for the drop being 56 mmHg (P less than 0.001). BP recovered to normal at 6 h. Acute group: Three SHRsp rats with BP 180.0 +/- 5.8 mmHg and weighing 231.0 +/- 11.2 g were anesthetized with sodium pentobarbital. AHF was injected into the femoral vein (0.35 mg/100 g BW). The results showed that the BP markedly decreased after administration of the extract, and the average value for the drop was 35 mmHg (P less than 0.05). The BP did not show any obvious change after injection of WKY rat extract.