Glucocorticoids cause growth retardation in children. We have studied the effect of these hormones on serum somatomedin (Sm) levels in seven children with nephrosis. Intravenous administration of methylprednisolone sodium succinate, 2.2 mg/kg, causes a rapid fall in serum Sm activity. The activity remains suppressed during continuous therapy, but returns toward normal when medication is omitted during the course of alternate-day therapy. We conclude that one reason for growth retardation secondary to continuous glucocorticoid therapy is suppression of Sm generation. A direct effect of these hormones on the cartilage cell or induction of an Sm inhibitor cannot be excluded by the reported experiments.

SummaryThe effect of somatomedin and cortisol on embryonic chick cartilage in vitro indicates that somatomedin stimulates 35S01 uptake while cortisol decreases it with no effect on glycosaminoglycan turnover. Xylosyltransferase activity is increased in crude fractions of somatomedin-treated cartilage but decreased in cortisol-treated cartilage. By using a Smith-degraded proteoglycan as an exogenous acceptor, xylosyltransferase activities from both treatments were equivalent, suggesting that the enzyme was not rate limiting. The results of xylosyltransferase assays conducted by mixing enzyme and endogenous acceptor from control, cortisoltreated, and somatomedin-treated cartilage, suggest both effects to be at the level of the acceptor protein.

No abstract

The glycosaminoglycan content of cartilage is decreased in manganese deficiency in the chick (perosis). The activity of xylosyltransferase, the first enzyme in the biosynthetic pathway of sulphated glycosaminoglycans, was studied in the epiphysial cartilage of 4-week-old chicks which had been maintained since hatching on a manganese-deficient diet. Enzymic activity was measured by the incorporation of [14C]xylose from UDP-[14C]xylose into trichloroacetic acid precipitates. Optimal conditions for the xylosyltransferase assay were established and shown to be the same for both control and manganese-deficient cartilage. Assay of the enzyme by using an exogenous xylose acceptor showed no difference in xylosyltransferase activity between control and manganese-deficient tissue. Further, the extent of xylose incorporation was greater in manganese-deficient than in control cartilage preparations, suggesting an increase in xylose-acceptor sites on the endogenous acceptor protein in the deficient cartilage. 35S turnover in the manganese-deficient cartilage was also increased. The data suggest that the decreased glycosaminoglycan content in manganese-deficient cartilage is due to decreased xylosylation of the acceptor protein plus increased degradation of glycosaminoglycan.