Metabolism of Glycine-1-C14by Bonein Vitro:Effects of Hormones and Other Factors

Abstract

The metabolism of glycine by bone cells in vitro has been examined, using surviving metaphysial bone fragments from rats and mice and glycine labeled with C¹⁴ in the carboxyl carbon as substrate. It has been possible to show that, while small amounts of glycine are decarboxylated (0.0013 μm/hr per 100 mg fresh bone), much larger amounts are incorporated intact into the organic matrix of incubated bone samples taken from 2-monthold rats (0.016 μm/hx per 100 mg bone). These rates vary with the age of the animal—being larger in young and smaller in older animals. The presence of glucose as substrate, and especially the percentage of O₂ in the gas phase of the incubation system, have been shown to be important variables in determining the rates of glycine metabolism by bone. In addition, a survey of hormonal influences on glycine metabolism in bone has been made. Hypophysectomy, cortisone and thyroxine in vitro and estradiol in vivo in rats have been shown to decrease, while insulin in vitro, growth hormone treatment of hypophysectomized animals and estradiol in mice have been shown to increase the rate of glycine incorporation into the organic matrix of incubated bone samples. The implications of these findings in defining pathways, rates and control of metabolism in bone are discussed.