Regulation of alpha 2-adrenergic receptor expression and signaling in pancreatic beta-cells

Am J Physiol. 1995 Jul;269(1 Pt 1):E162-71. doi: 10.1152/ajpendo.1995.269.1.E162.

Abstract

Activation of alpha 2-adrenergic receptors (alpha 2-AR) in pancreatic beta-cells inhibits insulin secretion in response to various stimuli, and acute or long-term regulation of alpha 2-AR receptor-mediated effects may influence the tissue response to glucose dishomeostasis. As an initial approach to this issue, we determined the effect of various metabolic and hormonal treatments on alpha 2-AR expression and coupling in the pancreatic beta-cell lines HIT-T15 and RIN-5AH. Radioligand binding studies ([3H]RX-821002) and RNA blot analysis indicate that both pancreatic beta-cell lines express the alpha 2A/D-AR subtype [for HIT-T15 the maximum binding (Bmax) = 113 +/- 28; for RIN-5AH Bmax = 93 +/- 18 fmol/mg of cellular protein]. Treatment of HIT-T15 or RIN-5AH cells with glucocorticoids [dexamethasone, hydrocortisone, or prednisolone (1 microM)] increased alpha 2-AR mRNA level and receptor protein density three- to fivefold. The glucocorticoid-induced increase in receptor density in HIT-T15 cells was associated with 1) an increase in the amount of receptors coupled to G protein as determined by analysis of high-affinity 5'-guanylyl imidodiphosphate-sensitive binding of [3H]UK-14304, a selective alpha 2-AR agonist, and 2) a greater inhibition of forskolin-induced elevation of cellular adenosine 3',5'-cyclic monophosphate after receptor activation. Receptor density in HIT-T15 cells was not altered by different growth conditions, insulin (1 microM), phorbol 12-myristate 13-acetate (1 microM), or the sex steroids testosterone and progesterone (1 microM). These data indicate that glucocorticoids upregulate alpha 2-AR expression and signaling in pancreatic beta-cells. Such regulation may operate in a cell-specific manner, allowing discrete modulation of tissue responses to glucose dishomeostasis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Cricetinae
  • Dexamethasone / pharmacology
  • Islets of Langerhans / physiology*
  • Mesocricetus
  • Rats
  • Receptors, Adrenergic, alpha / metabolism*
  • Signal Transduction*
  • Up-Regulation

Substances

  • Receptors, Adrenergic, alpha
  • Dexamethasone