EFFECTS OF GALANIN ON GROWTH-HORMONE RELEASE IN ISOLATED CULTURED RAT SOMATOTROPHS

Several studies suggest that galanin stimulates growth hormone release through effects on the hypothalamus. It is not known if galanin has acute effects directly on the somatotrophs. We now find that 0.5 mumol/l galanin stimulates growth hormone release within the first minute of exposure in isolated, purified, cultured male rat somatotrophs. The effect persisted for 15 min and was reversible when galanin was omitted. Galanin reduced the effect of 1 nmol/l growth hormone-releasing hormone (hGHRH(1-29)) on growth hormone release. Galanin stimulated Ca-45 efflux from prelabelled cells but had no effect on Rb-86 efflux (tracer for potassium). The findings support the fact that galanin can stimulate growth hormone release directly at the level of the somatotrophs. The cellular mechanisms for the effect of galanin probably differ from those of growth hormone-releasing hormone.