Conference Proceedings

Diverse intracellular signalling systems used by growth hormone-releasing hormone in regulating voltage-gated Ca2 or K channels in pituitary somatotropes

C Chen, RW Xu, IJ Clarke, M Ruan, K Loneragan, SG Roh

IMMUNOLOGY AND CELL BIOLOGY | BLACKWELL SCIENCE ASIA | Published : 2000

Abstract

Influx of Ca2+ via Ca2+ channels is the major step triggering exocytosis of pituitary somatotropes to release growth hormone (GH). Voltage-gated Ca2+ and K+ channels, the primary determinants of the influx of Ca2+, are regulated by GH-releasing hormone (GHRH) through G-protein-coupled intracellular signalling systems. Using whole-cell patch-clamp techniques, the changes of the Ca2+ and K+ currents in primary cultured ovine and human somatotropes were recorded. Growth hormone-releasing hormone (10 nmol/L) increased both L- and T-type voltage-gated Ca2+ currents. Inhibition of the cAMP/protein kinase A (PKA) pathway by either Rp-cAMP or H89 blocked this increase in both L- and T-type Ca2+ curr..

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