State of human growth hormone in plasma and changes in stored solutions of pituitary growth hormone.

Radioimmunoassay of endogenous plasma growth hormone in human plasma fractions separated by starch gel electrophoresis shows that the plasma hormone migrates in a fairly narrow peak behind serum albumin. A similar electrophoretic mobility is exhibited by certain pituitary growth hormone preparations (the A type of Wilhehni), added to plasma in physiological concentrations or on electrophoresis in the absence of plasma. Other pituitary growth hormone preparations (the B type of Wilhelmi) exhibit greater heterogeneity, with several more anodally migrating fractions. On prolonged storage in 5 X 10d3 M HCl at 15’ or after short periods in acid, neutral, or alkaline solutions at ZO-37’, increase in acidic components is observed in all preparations. Growth hormone preparations lightly iodinated with 1311 show electrophoretic mobilities similar to those of the respective unlabeled hormones, but more heavily iodinated preparations show greater anodal mobility. Immunoreactivities of A type and B type hormones were identical in an antiserum used for immunoassay of growth hormone in human plasma. It is concluded that the electrophoretic mobility of endogenous plasma growth hormone corresponds to that of unaltered pituitary growth hormone, that electrophoretic heterogeneity of pituitary growth hormone preparations is the consequence of deamidation or other alteration of native hormone, and that neither pituitary growth hormone added to plasma nor endogenous plasma hormone is bound to normal plasma proteins.