Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C.

Van Der Merwe, P; Millar, R; Davidson, J

Journal article

Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C.

Abstract:: Using permeabilized gonadotropes, we examined whether Ca2(+)-stimulated luteinizing-hormone (LH) exocytosis is mediated by the Ca2(+)-activated phospholipid-dependent protein kinase (protein kinase C). In the presence of high [Ca2+]free (pCa 5), alpha-toxin-permeabilized sheep gonadotropes secrete a burst of LH and then become refractory to maintained high [Ca2+]free. The protein kinase C activator phorbol myristate acetate (PMA) is able to stimulate further LH release from cells made refractory to high [Ca2+]free, suggesting that Ca2+ does not stimulate LH release by activating protein kinase C. Staurosporine, a protein kinase C inhibitor, inhibited PMA-stimulated (50% inhibition at 20 nM), but not Ca2(+)-stimulated, LH exocytosis. In cells desensitized to PMA by prolonged exposure to a high PMA concentration, Ca2(+)-stimulated LH exocytosis (when corrected for depletion of total cellular LH) was not inhibited. Ba2+ was able to stimulate LH exocytosis to a maximal extent similar to Ca2+, although higher Ba2+ concentrations were necessary. Ba2+ and Ca2+ stimulated LH exocytosis with a similar time course, and both were inhibitory at high concentrations. Furthermore, cells made refractory to Ca2+ were also refractory to Ba2+. These data strongly suggest that Ba2+ and Ca2+ act through the same mechanism. Since Ba2+ is a poor activator of protein kinase C, these findings are additional evidence against a major role for protein kinase C in mediating Ca2(+)-stimulated LH exocytosis.

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APA Style

Van Der Merwe, P., Millar, R., & Davidson, J. (1990). Calcium stimulates luteinizing-hormone (lutropin) exocytosis by a mechanism independent of protein kinase C. Biochemical Journal, 268(2), 493–498.

MLA Style

Van Der Merwe, P, et al. “Calcium Stimulates Luteinizing-Hormone (Lutropin) Exocytosis by a Mechanism Independent of Protein Kinase C.” Biochemical Journal, vol. 268, no. 2, 1990, pp. 493–98.

Chicago Style

Van Der Merwe, P, R Millar, and J Davidson. 1990. “Calcium Stimulates Luteinizing-Hormone (Lutropin) Exocytosis by a Mechanism Independent of Protein Kinase C.” Biochemical Journal 268 (2): 493–98.
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