Mechanism of isoprenaline-stimulated diacylglycerol formation in rat parotid acinar cells.
The kinetics and mechanism of sn-1,2-diacylglycerol (DAG) formation induced by isoprenaline were studied in rat parotid acinar cells. DAG accumulation induced by 100 microM isoprenaline reached its maximum at 1 min, rapidly decreased (about 50%) at 5 min and then remained constant for 30 min. DAG accumulation 1 min after isoprenaline treatment was dose-dependent. Either propranolol or phentolamine inhibited isoprenaline-stimulated DAG accumulation in a dose-dependent manner. Addition of a vasoactive intestinal polypeptide, forskolin, or dibutyryl cyclic AMP had no effect on DAG accumulation. Isoprenaline did not cause the release of [3H]choline or [3H]ethanolamine metabolites into the medium. Based on the kinetics of DAG formation and [32P]phosphoinositide breakdown, we conclude that isoprenaline-induced DAG formation was mainly related to the hydrolysis of [32P]phosphatidylinositol 4,5-bisphosphate ([32P]PIP2). These results suggest that the effect of isoprenaline on DAG formation is mediated by alpha 1-adrenoceptor activation, that it is not related to the increase in cyclic AMP, and that it is closely related to PIP2 hydrolysis.
Komabayashi
T
T
Department of Physiology and Pharmacology, Tokyo College of Pharmacy, Japan.
Noguchi
M
M
Izawa
T
T
Suda
K
K
Tsuboi
M
M
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004075:Diglycerides / Q000096:biosynthesis*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D010646:Phentolamine / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D019311:Staurosporine; D013268:Stimulation, Chemical; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D000470:Alkaloids; D004075:Diglycerides; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D018340:Receptors, Adrenergic, alpha-1; D011943:Receptors, Adrenergic, beta; D005576:Colforsin; D014660:Vasoactive Intestinal Peptide; D003994:Bucladesine; D011433:Propranolol; D011493:Protein Kinase C; D019311:Staurosporine; D007545:Isoproterenol; D010646:Phentolamine