Glomerular and Tubular α- and α-Adrenoceptors in the Rat Kidney: Distribution in Basolateral and Brush Border Membranes of Tubular Cells

Rat kidney glomeruli and cortical tubules were obtained by a combination of sieving and differential centrifugation technique. [H]Prazosin and [H]rauwolscine were used to identify and quantify the α- and α-adrenergic receptors, respectively. In the glomeruli, the α,-adrenoceptor concentration was 27% and α-adrenoceptor concentration was 33% of the corresponding values in the tubules. Further localization of the tubular α-adrenoceptors was undertaken by studies in the isolated basolateral membrane and comparison with values in the crude plasma membrane. α-Adrenoceptors were enriched 1.54 ± 0.1 times and α-adrenoceptors were enriched 1.73 ± 0.04 times in the basolateral membrane as compared to crude plasma membrane. However, these values were significantly (p < 0.05) less than the enrichment value of 2.77 ± 0.3 obtained for the basolateral membrane marker (Na + K )-ATPase. These results suggested the possibility that α- and α-adrenoceptors may also be distributed in the brush border membrane. Direct-binding studies in the purified renal brush border membrane indicated α-adrenoceptor concentration of 82.1 ± 3.8 and α-adrenoceptor concentration of 108.2 ± 9.3 fmol/mg protein. These values were 32 and 17% of the corresponding values in the basolateral membrane. Overall, our results suggest that α- and α-adrenoceptors are present both in the basolateral and brush border membranes analogous to what has been reported for angiotensin and insulin receptors; their primary concentration, however, is in the basolateral membranes.