Effects of a Massive Dose of Parathyroid Extract on Bone Metabolic Pathways

Abstract

The sequence of metabolic events in serum and bone which occur during the 48 hours following the injection of a single massive dose of parathyroid extract (PTE) into mice has been examined. Marked changes in serum P and Ca concentrations were observed beginning at 6 and 12 hours respectively, which subsequently returned to or toward normal by 48 hours. Some participation by bone in these changes even as early as 6 hours was indicated by an increase in the Ca concentration and a decrease in P concentration maintained by viable bone fragments in their bathing media in vitro. These bone effects, however, developed more slowly and were still increasing by 48 hours suggesting a slower and longer-lasting effect of the hormone preparation on the skeletal systems concerned with maintenance of Ca and P concentrations in the extracellular fluids. in vitro studies of carbohydrate metabolism using glucose-U-C₁₄ indicated that aerobic glycolysis was increased following PTE at all time intervals. However, no effect of PTE on the oxidative metabolism of glucose or on the incorporation of labeled carbon from glucose into the matrix of the bone fragments was observed. Studies of the in vitro incorporation of glycine-l-C₁₄ into bone matrix showed a sharp decrease in incorporation at 12 hours after hormone, a return to normal range at 24 hours, and a marked increase in incorporation at 48 hours. Oxidative decarboxylation of glycine and incorporation of the label into respiratory CO₂ was unchanged until the later periods when it was sharply decreased. Possible relations of changes in Ca and P metabolism to changes in bone cell metabolism and the observed effects of the hormone preparation on metabolic pathways in bone cells are discussed.