[Characterization of the alpha adrenoreceptors in the vascular bed of the isolated rat kidney].

The vasoconstrictive effect of alpha-adrenoceptor agonists was studied on isolated perfused kidney from normal Wistar rats. Methoxamine (ED50 = 1.61 +/- 0.16 X 10(-6) M; m +/- SEM), phenylephrine (2.33 +/- 0.16 X 10(-6) M) and alpha-methylnoradrenaline (1.60 +/- 0.40 X 10(-6) M) acted as full agonists. Dopamine (9.5 +/- 1.08 X 10(-5) M) had a partial agonistic effect. Clonidine and B-HT 920 were inactive up to the concentration of 10(-4) M. Prazosin, but not yohimbine (10(-6) M) antagonized the response to phenylephrine (pA2 = 8.48 +/- 0.12) and to alpha-methylnoradrenaline (8.02 +/- 0.10). Our results suggest that the postsynaptic alpha-adrenoceptors which when stimulated increases vascular resistance of isolated rat kidney, belong exclusively to the alpha 1-subtype.