Growth hormone receptors and action in BC3H-1 myocytes.

The muscles of the body are generally regarded as major targets for the actions of growth hormone (GH), but these tissues are difficult to utilize for in vitro studies of rapid cellular events. Therefore, the present study was conducted to determine whether the BC3H-1 cultured myocyte cell line possesses GH receptors and whether it exhibits metabolic responsiveness to GH. It was found that the myocytes possess receptors, which appear to be specific for GH and GH derivatives but which do not bind prolactin. The degree of GH binding observed was small, suggesting that receptors for GH are present in rather low abundance on these cells. To determine whether BC3H-1 myocytes are metabolically responsive to GH, the insulin-like activity of GH (i.e. the ability of GH to stimulate glucose metabolism) was examined, since this effect of GH is readily demonstrable when isolated rat muscle is incubated directly with the hormone. GH was found to stimulate glucose oxidation by the myocytes indicating that the receptors for GH on these cells are functional.