Parathyroid Extract-Induced Changes in the Oxidation of Citrate, Succinate and Other Organic Acids by Liver

Abstract

Parathyroid extract (PTE) or partially purified parathyroid hormone administered in vivo markedly altered the oxidation in vitro by rabbit liver minces of citrate, [alpha]-ketoglutarate, succinate, fumarate and lactate. With Ca++ present in the incubation medium, minces from PTE-treated animals produced more CO2 and had a greater O2 consumption than did control minces. This stimulation was due, in part at least, to a more rapid decline in metabolic activity of the control tissues. When Ca++ was absent, total metabolism was increased and the tissue derived from PTE-treated animals was less active than the control tissue. The effect was detected as early as 4 hr. after injection (750 U/kg) and could be elicited with as little as 200 U (at 14 hr.). The action of PTE could not be duplicated by the injection of CaCl2 into the animal. The data suggest that one effect of treatment was a general inhibition of oxidation. The stimulation of metabolism could be a consequence of this inhibition or a separate unrelated alteration.