Expression of multiple alpha-adrenoceptor isoforms in rat CCD.

Academic Article

Abstract

  • In the rat cortical collecting duct (CCD), epinephrine inhibits vasopressin (AVP)-dependent water permeability and Na+ reabsorption. Although inhibition is reversed by the alpha2-adrenoceptor (AR) antagonist yohimbine, suggesting the epinephrine effect is primarily mediated by an alpha2-AR [C. T. Hawk, L. H. Kudo, A. J. Rouch, and J. A. Schafer. Am. J. Physiol. 265 (Renal Fluid Electrolyte Physiol. 34): F449-F460, 1993], there are also suggestions of an effect at an additional receptor, perhaps an alpha1-AR. For the present experiments, we used RT-PCR of total RNA extracted from 1 to 5 mm of microdissected CCDs from rat kidney to identify the alpha-AR isoforms expressed. Specific primers for the alpha2-ARs amplifying from the 6th transmembrane (TM) to the 3'-untranslated regions, revealed the presence of alpha2A and alpha2B. Western blot analysis also indicated the presence of alpha2B-AR at the protein level. Degenerate alpha1-AR primers that amplify from conserved regions of TM-1 to TM-5, as well as specific primers that amplify either the same region (alpha1B), the carboxy terminus (alpha1A), or within the third cytoplasmic loop (alpha1D), indicated the presence of all three alpha1-ARs. Measurement of transepithelial voltage in isolated perfused renal tubules indicated a small inhibitory effect mediated by alpha1-ARs. Although the functional effects of epinephrine on AVP-dependent transport processes appear to be mediated predominantly by an alpha2-AR, a small contribution to the overall alpha-AR effect may be due to simultaneous activation of an alpha1-AR.
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    Keywords

  • Animals, Arginine Vasopressin, DNA Primers, Desoxycorticosterone, Epithelial Cells, Gene Expression Regulation, Kidney Cortex, Kidney Tubules, Collecting, Male, Membrane Potentials, Phentolamine, Phenylephrine, Polymerase Chain Reaction, Propranolol, Rats, Rats, Sprague-Dawley, Receptors, Adrenergic, alpha, Receptors, Adrenergic, alpha-1, Receptors, Adrenergic, alpha-2, Yohimbine
  • Digital Object Identifier (doi)

    Author List

  • Wilborn TW; Sun D; Schafer JA
  • Start Page

  • F111
  • End Page

  • F118
  • Volume

  • 275
  • Issue

  • 1