Abstract
Summary
Changes in canine renal blood flow in response to intra-arterial bolus injections of isoproterenol were studied in the presence and absence of adrenergic blocking agents. In the absence of blocking drugs, isoproterenol produced small increases in renal blood flow. Alpha-adrenergic blockade with phenoxybenzamine potentiated the vasodilator action of isoproterenol. In contrast, beta-adrenergic blockade with propranolol reversed the dilator action of isoproterenol to a marked constrictor action, which in turn was abolished by alpha-blockade. These results support the view that few responsive beta-receptors are present in renal vascular smooth muscle, and that isoproterenol can stimulate alpha-receptors, resulting in vasoconstriction.
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