Insulin and adenosine regulate the phosphatidylcholine concentration in isolated rat adipocyte plasma membranes.
Blockade of adenosine receptors by 3-isobutyl-1-methylxanthine or degradation of endogenous adenosine with adenosine deaminase increased the phosphatidylcholine concentration in isolated rat adipocyte plasma membranes, an effect which was suppressed by the phosphatidylethanolamine methyltransferase inhibitor, S-adenosyl-L-homocysteine, and reversed by the adenosine analogue, N6-(L-phenylisopropyl)-adenosine. For example, the addition of N6-(L-phenylisopropyl)-adenosine to adenosine deaminase pretreated plasma membranes rapidly lowered the concentration of phosphatidylcholine by 171 nmol/mg at 30 seconds compared to control. Insulin-induced stimulation of phospholipid methylation in membranes treated with 3-isobutyl-1-methylxanthine or adenosine deaminase was achieved only after the addition of N6-(L-phenylisopropyl)-adenosine. These results suggest that adenosine receptor occupancy inhibits phospholipid methylation, is required for insulin stimulation of phospholipid methylation, and may perhaps activate a phosphatidylcholine-specific phospholipase C or phospholipase D.
Kiechle
F L
FL
Department of Clinical Pathology, William Beaumont Hospital, Royal Oak, MI 48073, USA.
Sykes
E
E
Artiss
J D
JD
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology*; D000243:Adenosine Deaminase / Q000494:pharmacology; D017667:Adipocytes / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D010713:Phosphatidylcholines / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007328:Insulin; D010713:Phosphatidylcholines; D000243:Adenosine Deaminase; D000241:Adenosine; D015056:1-Methyl-3-isobutylxanthine