Summary
The effect of Cholecystokinin Octapeptide (CCK-8) on the release of growth hormone (GH) in rats was studied in vivo and in vitro. Intravenous injection of 5 μg/100 g BW of CCK-8 resulted in significant increase in the plasma GH level after 10 and 20 min. CCK-8 at concentrations of 10-11M to 10-7M also caused dose-dependent stimulation of GH release from dispersed cells of rat anterior pituitary. On the other hand, somatostatin (SRIF) inhibited GH release from dispersed cells of rat anterior pituitary in a dose-related manner at concentrations of 10-7M to 10-9M. Release of GH from the cells was increased by addition of K+ at high concentration (50 mM) in a Ca++-dependent manner. Addition of 10-3M verapamil to the incubation medium inhibited CCK-8-induced GH release from the cells. Addition of SRIF (10-7M) to the incubation medium inhibited GH release from the cells induced by CCK-8 or high K+ (50 mM).
These results indicate that CCK-8 acts directly on the anterior pituitary cells to stimulate GH release and that calcium ion is involved in the mechanism of this effect.
Key-Words:
Cholecystokinin Octapeptide
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Growth Hormone
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Somatostatin
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Verapamil
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Pituitary Cells
