Participation of kinins in the inhibitory action of captopril on acute hypertension induced by L-NAME in anesthetized rats

The aim of the present study was to investigate the role of bradykinin in the inhibitory action of captopril in hypertension induced by L-NAME in anesthetized rats. Male Wistar rats (260-320 g) were anesthetized with chloralose and arterial blood pressure was recorded with a polygraph pressure transducer. The hypertensive effect of L-NAME was studied in rats pretreated with saline, captopril or HOE 140 plus captopril. The effect of captopril was also studied during the sustained presser effect of L-NAME. The acute presser effect of L-NAME (10 mg/kg, iv) was significantly reduced by iv pretreatment with 2 mg/kg captopril (Delta increase of 49 +/- 4.9 mmHg reduced to 20 +/- 5.4 mmHg, P = 0.01), The presser effect of L-NAME (Delta increase of 38 +/- 4.8 mmHg) observed in rats pretreated with captopril and HOE 140 (0.1 mg/kg, iv) was not significantly different from that induced by L-NAME in rats pretreated with saline (P = 0.09). During the sustained presser effect induced by L-NAME (Delta increase of 49 +/- 4.9 mmHg) captopril induced a significant (P<0.05) reduction in arterial blood pressure (Delta decrease of 22 +/- 3.0 mmHg). The present results demonstrate that the acute presser effect of L-NAME is reduced by captopril and this inhibitory effect may be partly dependent on the potentiation of the vasodilator actions of bradykinin.