Beta-adrenoceptors in kidney tubules of spontaneously hypertensive and normotensive rats

Beta-adrenoceptor binding characteristics were determined in different fractions of rat kidney tubules using a [125Iodo]-(-)-cyanopindolol (ICYP) binding assay. The highest amount of binding sites was found in a fraction containing predominantly distal tubular fragments. In a separate series of experiments the ICYP binding characteristics were compared in whole tubular fractions from spontaneously hypertensive (SHR) and normotensive Wistar Kyoto rats (WKY) of different ages. The maximum number of binding sites was significantly higher both in young (3 weeks) and adult (14 weeks) SHR when compared to age-matched WKY. These studies showed the presence of beta-adrenoceptor binding sites in rat kidney tubules and support the potential importance of tubular beta-adrenoceptors in the development of spontaneous hypertension and in the mechanism of antihypertensive action of beta-blockers.