Inhibitory Effects of Amine Compounds on the Conversion of Bovine Proparathyroid Hormone to Parathyroid Hormone in vitro

Abstract

The effects of various amine compounds on the conversion of ProPTH to PTH in bovine parathyroid slices were studied. Bovine parathyroid slices were incubated in Earle's balanced salt solution with or with-out the designated amine compound (pH 7.4) at 37°C for up to 120 minutes. 3H-leucine was added to the incubation medium 30 to 60 minutes before termination of incubation. The incubated tissue slices and medium were homogenized together in 8M urea, 0.2N HCl and 0.01M cysteine solution by Polytron homogenizer. A crude hormonal extract as TCA-powder was prepared through fractionation with organic solvent and salt followed by precipitation of the hormonal peptides with 7.5% TCA. The TCA-powder was further fractionated through CM-cellulose chromatography in order to separate radioactive ProPTH from PTH. Primary, secondary and tertiary amines as well as inorganic ammonium compounds, especially ammonium chloride (pH 7.4), inhibited the conversion of ProPTH to PTH, while quarternary amine, diamine and polyamine did not. Monoamine-induced inhibition of the conversion of ProPTH to PTH was time- and dose-dependent. Such inhibition by amines of the conversion of ProPTH to PTH was reversible in diethylamine and irreversible in tris (OH) methyl-aminomethane.