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1. The effect of alpha-adrenergic stimulation, with phenylephrine, on isoprenaline-provoked renin secretion was studied in the isolated perfused rat kidney. 2. Infusion of phenylephrine increased renal perfusion pressure and prevented renin secretion in response to isoprenaline. 3. Renal vasoconstriction was abolished and the response in renin secretion to isoprenaline was restored by alpha-adrenoreceptor blockade with phenoxybenzamine. 4. In contrast, when renal vasoconstriction was prevented by dihydrallazine, suppression of renin release by phenylephrine still occurred. 5. These observations support an inhibitory effect of a non-vascular alpha-adrenergic mechanism on renin release. It is suggested that the alpha-receptor mediating this effect is directly related to the renin-producing juxtaglomerular cell.