Studies on the Biosynthesis in Vitro of Parathyroid Hormone

Abstract

Abstract Bovine parathyroid gland slices were incubated in vitro in buffers containing concentrations of calcium in the range of 0.5 mm to 2.0 mm and magnesium in the range of 0.2 mm to 1.7 mm and either a 3H- or a 14C-amino acid. After incubation, radioactive parathyroid hormone was isolated from both the tissue and the incubation medium by a combination of methods including gel filtration and ion exchange chromatography. The isolation, localization, and quantification of parathyroid hormone present at various stages of purification was assisted by adding to the samples, prior to processing, small amounts of biologically synthesized, highly purified radioactive parathyroid hormone as an internal standard. The use of the internal standard to correct for losses of parathyroid hormone during processing was particularly necessary due to the finding that a large fraction of radioactive parathyroid hormone in the experimental samples could be adsorbed to the chromatographic columns employed to isolate the hormone. When the concentration of calcium was lowered, there was an increase in radioactive parathyroid hormone isolated from both the tissue and the medium. In contrast, changes in magnesium concentration had no effect on the biosynthesis of parathyroid hormone. The hormonal species obtained from tissue and the one isolated from incubation medium migrated in an identical fashion during chromatography on gels and upon electrophoresis, indicating that this species was similar to that extracted from the tissue.