In Vitro Secretion of Calcitonin from a Rat C Cell Line:

Summary

Calcium and BAY K 8644 acutely stimulate calcitonin secretion by influx of extracellular calcium (Ca) through voltage-dependent calcium channels, leading to an increase in cytosolic free Ca. Repetitive exposure to BAY K 8644 (10^-6M) resulted in an increase in calcitonin (CT) secretion in the rat C-cell line (rMTC 6-23) lasting 9 hours, in comparison to that of 3 mM Ca²⁺ which lasted 6 hours. Equimolar concentration of nifedipine did not inhibit the stimulatory effect of BAY K 8644 as compared to the nifedipine only group. The decrease in stimulated CT secretion during long-term exposure to BAY K 8644 is due to desensitization of cells which may be attributed to down-regulation of dihydropyridine receptors. After 12 h exposures to 3 mM Ca²⁺ alone, BAY K 8644 (10^-6M) alone or in combination with nifedipine (10^-6 M), CT content decreased below the control level, indicating a decrease in synthesis. Overall cellular protein content was not affected by the test agents. Repetitive exposure of C-cells to BAY K 8644 revealed a desensitization of the stimulatory effect on CT secretion and a decrease in CT cell content.

Key words

Calcitonin - Secretion and Content - Calcium Channel - BAY K8644 - C-Cell Line (rMTC 6-23)