The calcium agonist Bay K 8644 stimulates secretion from a pituitary cell line.

The dihydropyridine calcium agonist Bay K 8644 acts in a dose-dependent manner to increase prolactin secretion from the GH4C1 pituitary cell line. Enhanced secretion was observed at agonist concentrations as low as 10 nM. In the continued presence of Bay K 8644 secretion remained elevated for at least 30 min. The effect of the agonist was Ca2+-dependent and competitively antagonized by dihydropyridine antagonists. Apparently Bay K 8644 acts at the dihydropyridine binding site associated with GH4C1 Ca2+ channels to enhance Ca2+ influx and stimulate secretion from these cells. This is the first report demonstrating that the newly discovered Ca2+ agonist can, by itself, stimulate secretion from a cell.