Rapid suppressing action of insulin-like growth factor-I (IGF-I) on GH release from anterior pituitary cells of goats.
Goat anterior pituitary cells were cultured to investigate the effects of insulin-like growth factor-I (IGF-I), insulin, and growth hormone (GH) on basal and GH-releasing hormone (GHRH)-induced GH release. Changes in cellular Ca2+ concentrations were also assessed to enable discussion of the cellular mechanisms of IGF-I. The cells were cultured for 48 h, and then stimulated with GHRH (10 nmol/l) for 30 min, with or without each test substance. In the control cells, IGF-I (10 and 100 ng/ml) significantly raised the basal, but did not change GHRH-induced GH release, resulting in the abolishment of GH release induced by GHRH in the presence of 100 ng/ml IGF-I. However, there was no significant effect of insulin (10, 100, and 1000 microU/ml) on basal and GHRH-induced GH release. In the cells cultured for 48 h with each test substance but stimulated for 30 min without the test substance, no significant change in the basal and GHRH-stimulated GH release was observed. Regardless of treatment, there was no significant effect on intra-cellular GH content. Analysis with a confocal laser microscope revealed that IGF-I (100 ng/ml) significantly increased the basal, but significantly reduced GHRH (10 nmol/l)-induced increase in cellular Ca2+ concentrations. From these findings we conclude that IGF-I exerts an acute suppressing action on the GHRH-induced GH release, which partly involves changes in cellular Ca2+ metabolism in goat somatotrophs.
Katoh
K
K
Department of Animal Physiology, Graduate School of Agriculture, Tohoku University, Tsutsumidori, Aoba-ku, Sendai 981-8555, Japan. kato@bios.tohoku.ac.jp
Shimoguchi
R
R
Ishiwata
H
H
Obara
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D006041:Goats / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism* / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*
D007328:Insulin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D002118:Calcium