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

Artikel i vetenskaplig tidskrift
Författare X Xu
G De Pergola
Peter S Eriksson
Michael Fu
B Carlsson
S Yang
Staffan Edén
Per Björntorp
Publicerad i Endocrinology
Volym 132
Nummer/häfte 4
Sidor 1651-7
ISSN 0013-7227
Publiceringsår 1993
Publicerad vid Wallenberglaboratoriet
Hjärt-kärlinstitutionen
Institutionen för fysiologi och farmakologi, Avdelningen för fysiologi
Sidor 1651-7
Språk en
Länkar www.ncbi.nlm.nih.gov/entrez/query.f...
Ämnesord Adenylate Cyclase, metabolism, Adipose Tissue, cytology, metabolism, Animals, Cells, Cultured, Cholesterol Esterase, metabolism, Enzyme-Linked Immunosorbent Assay, GTP-Binding Proteins, genetics, metabolism, Male, Orchiectomy, Protein Kinases, metabolism, RNA, Messenger, metabolism, Rats, Receptors, Adrenergic, beta, physiology, Testosterone, pharmacology, Up-Regulation, physiology
Ämneskategorier Fysiologi, Cell- och molekylärbiologi

Sammanfattning

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.

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