Two effects of lysophosphatidic acid on Ca(2+)-movement in cultured bovine adrenal chromaffin cells.
We found that lysophosphatidic acid (LPA) exerted two effects on Ca(2+)-movement in cultured bovine adrenal chromaffin cells. At concentrations of above 10(-5) M, it induced slight, but significant 45Ca2+ influx, resulting in release of a small portion of stored catecholamine. At high concentrations it also significantly increased the intracellular Ca2+ concentration in Fura-2-loaded cells. At concentrations as low as 10(-7) M, it stimulated extracellular Na(+)-dependent 45Ca2+ efflux, possibly by increasing Na+/Ca2+ exchange. The maximal efflux of Ca2+ attained with 10(-5) M LPA was inhibited by tyrosine kinase inhibitors, but augmented by a protein kinase C inhibitor. These results suggest that LPA-induced Ca2+ efflux is controlled positively and negatively by mechanisms involving tyrosine kinase and protein kinase C, respectively.
Tokumura
A
A
Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
Okuno
M
M
Fukuzawa
K
K
Houchi
H
H
Oka
M
M
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016257:Fura-2; D008246:Lysophospholipids / Q000494:pharmacology*
D002395:Catecholamines; D008246:Lysophospholipids; D002118:Calcium; D016257:Fura-2