Enhanced pressor response to angiotensin III in spontaneously hypertensive rats: effects of losartan.

The conscious spontaneously hypertensive rat (SHR), compared to its normotensive control Wistar Kyoto rat (WKY), exhibited a significantly greater pressor response to i.v. angiotensin II and angiotensin III. Losartan (10 mg/kg i.v.) lowered the basal blood pressure of the SHR but had no significant effect on that of the WKY. However, it attenuated the pressor response to both angiotensins in the SHR and WKY, the degree of attenuation being significantly greater with angiotensin III. In addition, the pressor responses induced by both angiotensin II and angiotensin III in the WKY, compared to those of the SHR, were more markedly inhibited by losartan. The results indicate a possible over-expression of angiotensin AT1 receptors in the SHR, and that both angiotensin II and angiotensin III contribute to the hypertension by acting on these receptors.