AUTORADIOGRAPHIC EVIDENCE FOR A HETEROGENEOUS DISTRIBUTION OF α1‐ ADRENORECEPTORS LABELLED BY [3 H] PRAZOSIN IN RAT, DOG AND HUMAN KIDNEY

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Abstract
The selective αradrenoreceptor antagonist radioligand [3 H] prazosin has been used to localize α1 adrenoreceptors in slide mounted sections of rat, dog and human kidney. The biochemical characteristics of [3 H] prazosin binding to rat kidney sections were examined and found to be saturable, reversible, stereoselective, with a KD of 0.12 nM and Bmax of 6.72 ± 0.2 fmoles/section. 3 H Ultrofilm images of [3 H] prazosin binding to rat, dog, and human kidney revealed binding to the vasculature but in the rat additional receptors were confined to the renal cortex. In the rat kidney autoradiography using emulsion coated coverslips showed that binding in the renal cortex was largely to proximal tubules. In all three species the autoradiographic studies support a role for α1‐adrenoreceptors in control of renal blood flow. In the rat the location of α1‐adrenoreceptors suggests that they can also have an important influence on fluid and electrolyte balance, gluconeogenesis and production of prostanoids.