Human Somatomedin, the Growth Hormone-Dependent Sulfation Factor, Is Anti-Lipolytic

Abstract

A partially purified, insulin-free preparation of human somatomedin, the newly proposed designation for the growth hormonedependent plasma sulfation factor, produced profound inhibition of in vitro glycerol release in epinephrine-stimulated rat epididymal fat pad segments. The log-dose response curves for inhibition of epinephrine-stimulated glycerol release by somatomedin and crystalline insulin were parallel. In this system, one unit of human somatomedin was equivalent to 120 μU of porcine insulin in anti-lipolytic activity. The ip administration of somatomedin to rats 4 hr before sacrifice resulted in the in vitro inhibition of epinephrine-stimulated glycerol release. Demonstration of the anti-lipolytic, insulin-like effects of somatomedin lends support to the possibility that sulfation/thymidine factor activity and non-suppressible insulin-like activity are resident in the same molecular species.