Ca2(+)-mobilizing hormones stimulate Ca2+ efflux from hepatocytes - PubMed (original) (raw)

. 1989 Dec 15;264(35):20863-6.

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Ca2(+)-mobilizing hormones stimulate Ca2+ efflux from hepatocytes

S K Duddy et al. J Biol Chem. 1989.

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Abstract

Treatment of hepatocytes with 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ), a novel mobilizer of the inositol 1,4,5-trisphosphate-sensitive Ca2+ pool, produces a sustained elevation of [Ca2+]i (Kass, G. E. N., Duddy, S. K., and Orrenius, S. (1989) J. Biol. Chem. 264, 15192-15198). Exposure of hepatocytes to the Ca2(+)-mobilizing hormones, vasopressin, angiotensin II, or ATP following [Ca2+]i elevation by tBuBHQ produced a rapid return of [Ca2+]i to basal or near basal levels. Release of the inositol 1,4,5-trisphosphate-sensitive Ca2+ pool by tBuBHQ following pretreatment with vasopressin or angiotensin II resulted in a [Ca2+]i transient and not the sustained [Ca2+]i elevation observed in the absence of the Ca2(+)-mobilizing hormones. The G-protein activator, NaF plus AlCl3, mimicked both effects of the Ca2(+)-mobilizing hormones on [Ca2+]i. The mechanism for Ca2+ removal from the cytosol by Ca2(+)-mobilizing hormones did not involve cyclic nucleotides nor did it require protein kinase C activation or cyclo- and lipoxygenase-dependent metabolites of arachidonic acid. Furthermore, the hormone-mediated decrease in [Ca2+]i did not involve the pertussis toxin-sensitive Gi-protein. Removal of the tBuBHQ-mobilized Ca2+ from the cytosol of hepatocytes by Ca2(+)-mobilizing hormones was mediated by stimulation of a Ca2+ efflux pathway. Thus, in addition to initiating [Ca2+]i transients by releasing Ca2+ from the inositol 1,4,5-trisphosphate-sensitive Ca2+ store and stimulating Ca2+ influx, Ca2(+)-mobilizing hormones also regulate the termination of the [Ca2+]i transient by stimulating a Ca2+ efflux pathway.

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