In vitro metabolic effects of proteolytic digests of bovine growth hormone in adipose tissue

Proteolytic digests of bovine growth hormone (BGH) prepared by controlled tryptic (TBGH) or papain (PBGH) digestion have in vitro metabolic properties which are qualitatively indistinguishable from native BGH preparations when evaluated by their ability to effect glucose- 14C uptake, its oxidation to CO 2 and incorporation in lipid, glycerol release, and histidine incorporation into protein of adipose tissue obtained from hypophysectomized rats. Chromatographic fractions of TBGH vary as to their relative potencies in stimulating these responses, both with respect to each other and with respect to the total TBGH digest. One fraction of TBGH formed from BGH by the proteolysis of 2–3 peptide bonds, possesses all the qualitative metabolic effects in vitro while exhibiting a moderate loss in potency both in vitro and in growth-promoting activity. Fractions of PBGH had activities similar to the PBGH digest.