Efflux of 45Ca2+ from human fibroblasts in response to serum or growth factors.
Previous studies have indicated that intracellular Ca2+ is involved in fetal bovine serum (FBS)- or growth factor (GF)-stimulated Na+ influx in human foreskin fibroblasts (HSWP). In the present study, 45Ca2+ efflux from serum-deprived HSWP cells was measured in response to 10% FBS or GF [lys-bradykinin, vasopressin, epidermal growth factor, and insulin]. Efflux data were analyzed using a computer program and the best fit indicated the presence of three Ca2+ compartments: a compartment (C1) with a very fast turnover rate, one (C2) with a fast turnover rate, and one (C3) with a slow turnover rate. When serum-deprived cells were treated with 10% FBS, efflux from C2 and C3 increased significantly (p less than 0.05). Similar effects on efflux were observed when serum-deprived cells were treated with individual GFs. Combination of the four GFs produced a higher stimulation than any single factor and a response that was equal to that of FBS. On the other hand, when cells were serum-treated in the presence of the intracellular Ca2+ antagonist, B-(N-N,diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), 45Ca2+ efflux from C2 was substantially reduced. Finally, when cells were treated with the Na+ transport inhibitor amiloride, there was no significant effect on serum-stimulated Ca2+ efflux. These results are consistent with a FBS- or GF-induced mobilization of Ca2+ that can be blocked by intracellular Ca2+ antagonists, and support the hypothesis that the action of these agents on Na+ influx may be via their effects on intracellular Ca2+.
D000584:Amiloride / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000502:physiology*; D002451:Cell Compartmentation / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000502:physiology; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006133:Growth Substances / Q000502:physiology*; D006801:Humans; D012964:Sodium / Q000502:physiology
D006133:Growth Substances; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D000584:Amiloride; D012964:Sodium; D002118:Calcium