A possible role for Ca 2+ and calmodulin in the action of growth-hormone-releasing factor (GHRF) was investigated. Low extracellular Ca2+ (<100 μM), methoxyverapamil, flunarizine, cinnarizine, and Co2+ decreased both basal and GHRF-stimulated growth-hormone secretion, but did not totally inhibit GHRF-stimulation secretion. A calmodulin antagonist, W7, abolished GHRF-stimulated GH secretion, with no effect on basal secretion. It is suggested that GHRF may act primarily by elevating cellular cyclic AMP, which may then modulate calcium mobilization or flux; the increased intracellular Ca2+ concentrations may then activate calmodulin.
Studies on the involvement of calcium and calmodulin in the action of growth-hormone-releasing factor
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Janet E. Merritt, Pauline R. M. Dobson, Richard J. H. Wojcikiewicz, John G. Baird, Barry L. Brown; Studies on the involvement of calcium and calmodulin in the action of growth-hormone-releasing factor. Biosci Rep 1 December 1984; 4 (12): 995–1000. doi: https://doi.org/10.1007/BF01116691
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