Growth Hormone Stimulation of Glucose Transport in Isolated Rat Hepatocyte Suspensions and Primary Cultures*

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Abstract
[14C]-3-O-Methyl-D-glucose transport in response to GH stimulation was measured in freshly prepared and cultured hepatocytes from hypophysectomized (hypox) adult female rats. Sugar transport in freshly isolated hepatocytes from hypox animals was stimulated by 10-9 M human GH (hGH) and 10-9 M rat GH (rGH) during 0–30 and 60–90 min of incubation, respectively. Monosaccharide transport in freshly isolated hepatocytes from normal female rats was unaffected by either hGH or rGH addition. Specific [125I]iodo-hGH binding to freshly isolated hepatocytes from hypox rats was detectable as early as 9 min of incubation and reached maximum binding levels by approximately 30–60 min. Specific [125I]iodo-rGH binding was not detectable until 30 min of incubation and reached a binding plateau after 60 min of incubation. Porcine insulin at 10-9 and 10-7 M was ineffective in stimulating sugar transport in either freshly isolated or cultured hepatocytes from hypox animals. Sugar transport in cultured hepatocytes was stimulated by 10-7 M hGH and 10-7 rGH, with 30–60 and 60–90 min of incubation being the most frequent stimulatory intervals observed. Maximum specific [125I]iodo-hGH binding was observed at 60 min of incubation and decreased by 72% and 77% at 90 and 120 min, respectively. Specific [l125I]iodo-rGH binding, however, was not detectable in cultured hepatocytes. Both hGH and rGH at 10-9 M stimulated glucose oxidation to CO22 in freshly isolated hepatocytes from hypox animals. Stimulation was observed after 30 min of incubation with GH and indicated a regulatory function for GH in maintaining basal levels of glucose oxidation. The results presented here suggest a possible role for GH in glucose uptake and metabolism in the liver and indicate that differences may exist between the effects of hGH and rGH on glucose uptake.

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