Postreceptor events involved in the up-regulation of beta-adrenergic receptor mediated lipolysis by testosterone in rat white adipocytes

Endocrinology. 1993 Apr;132(4):1651-7. doi: 10.1210/endo.132.4.8384992.

Abstract

In the previous studies we have shown that testosterone increases lipolytic responsiveness to catecholamines in rat white adipocytes, and that is associated with an up-regulation of beta-adrenergic receptor density. However, the postreceptor events involved in the testosterone induced enhancement of beta-adrenergic receptor activated lipolysis in these cells have not been adequately studied, and were therefore investigated in the present study. Male Sprague Dawley rats were divided into three groups: control, castrated, and castrated treated with testosterone. The beta-adrenergic receptor-mediated cAMP accumulation, measured with RIA after isoproterenol (a beta-adrenergic agonist) stimulation was decreased in castrated rats, and reversed by testosterone treatment, suggesting a testosterone effect at or proximal to adenylate cyclase. However, no differences between the groups were found in abundance of G alpha protein messenger RNAs (G alpha s, G alpha i-1, and G alpha i-2) as analyzed by Northern blot and a solution hybridization RNase protection assay, or in G protein mass measured with a quantitative enzyme-linked immunosorbent assay in fat cell membrane preparation. Lipolysis stimulated by N6-monobutyryl-cAMP was reduced in castrated rats and recovered by testosterone treatment, suggesting that components distal to the adenylate cyclase, i.e. protein kinase A (PKA) and/or hormone sensitive lipase (HSL) also are involved in testosterone regulation of lipolysis. In conclusion, these and previous results suggest that the testosterone-induced increase in lipolytic response to catecholamines in rat white adipocytes is mediated through several events including an increased beta-adrenergic receptor density, probably an increased adenylate cyclase activity and an increased protein kinase A/hormone sensitive lipase activity at the postreceptor level with apparent absence of effect on the expression of G-proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenylyl Cyclases / metabolism
  • Adipose Tissue / cytology
  • Adipose Tissue / metabolism*
  • Animals
  • Cells, Cultured
  • Enzyme-Linked Immunosorbent Assay
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism
  • Male
  • Orchiectomy
  • Protein Kinases / metabolism
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Adrenergic, beta / physiology*
  • Sterol Esterase / metabolism
  • Testosterone / pharmacology*
  • Up-Regulation / physiology*

Substances

  • RNA, Messenger
  • Receptors, Adrenergic, beta
  • Testosterone
  • Protein Kinases
  • Sterol Esterase
  • GTP-Binding Proteins
  • Adenylyl Cyclases