α- and β-adrenergic receptors in proximal tubules of rat kidney

Proximal tubules were isolated from the rat kidney by collagenase digestion of the cortical tissue followed by Percoll gradient centrifugation. Microscopic and hormone-stimulated adenylate cyclase activity studies proved the purity of the preparation. [3H]Prazosin, [3H]rauwolscine, and [125I]iodocyanopindolol were used to identify and quantitate respectively the α1-, α2- and β-adrenergic receptors. Proximal tubular (F4) particulate fraction was compared against other cortical nephron segment (F1,F2) fractions and the total collagenase-digested cortex particulate suspension (Ft). Proximal tubules were enriched in α1- and α2-adrenergic receptors compared with. The fractions enriched in glomeruli and distal tubular segments had relatively low concentrations of α1- and α2-adrenergic receptors. Isoproterenol-stimulated adenylate cyclase activities in the different fractions corroborated well with the pattern suggested by the [125I]iodocyanopindolol binding studies. The results suggest that whole-cortex preparation radioligand binding studies may reflect proximal tubular α1- and α2-adrenergic receptor changes quite well. They may, however, miss or give erroneous impressions about β-adrenergic receptor changes occurring in different cortical nephron segments