Localization of Dopamine Receptors in the Rabbit Renal Artery: A Histoautoradiographic Study

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Abstract
The localization of dopamine receptors within rabbit renal artery was studied using 3H-spiroperidol as a label for dopamine receptors and a histoautoradiographic technique. Preliminary radioreceptor binding studies showed that 3H-spiroperidol was bound to sections of renal artery in a manner consistent with the existence of dopamine receptors. In fact the binding was found to be saturable, stereospecific and of high affinity, with a Bmax approximately of 158.3 fmol/mg protein and a Kd of 13.5 nmol/l. The microscopic examination of sections processed for the histoautoradiographic demonstration of 3H-spiroperidol binding sites showed that the distribution of dopamine receptors in the renal artery was widespread. The highest concentration of dopamine receptors was found primarily in the smooth muscle cells of the media and then, in the following order, in endothelial cells of the intima and in fibrous and connective cells of the adventitia. The direct demonstration of dopamine receptors in the media of rabbit renal artery strongly supports the hypothesis that these receptors may be involved in the relaxation of the artery caused by infusion or application of dopamine.