title: Alpha- and beta-adrenergic receptors in proximal tubules of rat kidney.
abstract: 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 alpha 1-, alpha 2- and beta-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 alpha 1- and alpha 2-adrenergic receptors compared with Ft (alpha 1-receptor, 100.4 +/- 4.5 vs. 87.4 +/- 4.9; alpha 2-receptor, 250 +/- 16.2 vs. 185.1 +/- 12 fmol/mg protein). The fractions enriched in glomeruli and distal tubular segments (F1, F2) had relatively low concentrations of alpha 1- and alpha 2-adrenergic receptors. In contrast, beta-adrenergic receptor concentration in the proximal tubules was approximately 25% of that in the Ft fraction and approximately 10% of that in the F1 fraction. Isoproterenol-stimulated adenylate cyclase activities in the different fractions corroborated well with the pattern suggested by the [125I]iodocyanopindolol binding studies. Our results suggest that whole-cortex preparation radioligand binding studies may reflect proximal tubular alpha 1- and alpha 2-adrenergic receptor changes quite well. They may, however, miss or give erroneous impressions about beta-adrenergic receptor changes occurring in different cortical nephron segments.
authors.affiliation: Department of Pharmacology, University of Rochester Medical Center, New York 14642.
authors.forename: P R
authors.initials: PR
authors.lastname: Sundaresan
authors.forename: T L
authors.initials: TL
authors.lastname: Fortin
authors.forename: S L
authors.initials: SL
authors.lastname: Kelvie
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002499:Centrifugation, Density Gradient; D000242:Cyclic AMP / Q000378:metabolism; D020120:Iodocyanopindolol; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D009399:Nephrons / Q000378:metabolism; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D015016:Yohimbine / Q000378:metabolism
chemical_list: D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D015016:Yohimbine; D020120:Iodocyanopindolol; D010869:Pindolol; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D011224:Prazosin