| Abstract: | The effects of cortisol, estradiol, and testosterone on somatomedin action on cartilage incubated in vitro have been examined. The addition of hormones in the absence of serum had no effect on the incorporation of sulfate by cartilage from hypophysectomized rats, embryonic chicks, or normal young pigs. Normal human serum provided a source of somatomedin which stimulated the incorporation of sulfate by cartilage in a dose-response relationship; the potency of serum with and without added steroid hormone was determined after formal parallel-line analysis. Moderately supraphysiologic levels of cortisol, 17 beta-estradiol, and testosterone generally had little effect on somatomedin action in the test systems. Very high levels of serum cortisol (100-1000 mug/100 ml) inhibited somatomedin action on pig cartilage, but had little effect on rat or chick cartilage. A 20 ng/100 ml increase in serum estradiol had no effect on somatomedin action on chick cartilage, but appeared to enhance somatomedin action on pig cartilage. A 5 mug/100 ml increase in serum testosterone did not affect somatomedin action on either chick or pig cartilage. These studies suggest that the alteration of somatomedin action is not a major mechanism in the effect of steroid hormones on growth. In addition, since modest increases in serum levels of cortisol, estradiol, and testosterone had little effect on somatomedin action in our assay systems, these systems should be satisfactory for the study of hormone effects on somatomedin generation. |
