Effects of acute and prolonged glucose excess on growth hormone release by cultured rat anterior pituitary cells.
The aim of this study was to verify whether prolonged exposure of cultured rat anterior pituitary cells to high glucose can alter growth hormone (GH) release and responsiveness to secretagogues. Therefore, we cultured anterior pituitary cells obtained from normal male Sprague-Dawley rats in presence of normal (6 mM) or high (22 mM) glucose concentrations. After 3 days, the acute effects of glucose, growth hormone-releasing factor (GRF), dibutyryl cyclic AMP(db-cAMP) and somatostatin were studied during 2-hour incubations. High glucose did not alter basal GH release from cells cultured in 6 mM glucose. However, basal GH release from cells cultured in 22 mM glucose was moderately higher in the 2-hour incubation (by 46%) than in cells cultured in 6 mM glucose. In contrast, GH stimulation by GRF or db-cAMP was significantly reduced in cells cultured in 22 mM as compared to cells cultured in 6 mM glucose. This inhibitory effect of high glucose on GRF-stimulated GH release was completely reversible after 24 h of exposure of the cultured cells to 6 mM glucose and testing on the 4th day of culture. Finally, GH inhibition by somatostatin was also attenuated in cells cultured with high glucose. We conclude that prolonged exposure to high glucose could act directly at the pituitary level to modulate GH release and responsiveness.
Renier
G
G
Metabolic Unit, Research Center, Notre-Dame Hospital, Montreal, Canada.
Serri
O
O
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology
D013004:Somatostatin; D003994:Bucladesine; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D005947:Glucose