Abstract
Abstract 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 Wilhelmi), 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 10-3 m HCl at -15° or after short periods in acid, neutral, or alkaline solutions at 20–37°, increase in acidic components is observed in all preparations. Growth hormone preparations lightly iodinated with 131I 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.
Highlights
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
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
Yalow boundary was carefully removed and assayed for endogenous and labeled hormone as previously described for insulin [12]. Total recovery of both endogenous plasma hormone and added pituitary hormone from starch gel segments averaged about 80% by comparison with the original plasma and a similar percentage recovery was obtained with i3iI-labeled human growth hormone
Summary
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. Chen and Wilhelmi have found that the B type hormone has 1 to 2 amide groups less than the A type hormone,l which would account for the different electrophoretic mobilities of the labeled preparations. To determine the nature of “native” growth hormone, we have compared electrophoretic mobilities of endogenous plasma growth hormone and of various pituitary growth hormone preparations in starch gels. 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
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