Degradation of the parathyroid hormone in the kidney and liver (author's transl)]

The cleavage of the parathyroid hormone has been reported to take place in various peripheral tissues, especially in the kidney and liver. In order to claify the mechanism of such a degradation, bovine PTH (bPTH 1--84) and its synthetic N-terminal peptide (bPTH 1--34) labelled with 125I by the chroramine-T method (125I-bPTH 1--84) and (125I-bPTH 1--34) or labelled with horseradish peroxidase Pox-125I-bPTH 1--84 and Pox 125I-bPTH 1 34) were used to study the disappearance from the blood stream and degradation and retension in the kidney and liver after intravenous injections in male Wiastar rats, weighing approximately 200g. Degradation of PTH was also studied in vitro, using isolated cells and a homogenate of the kidney and liver. PTH labeled with 125I and Pox was more readily degraded by the kidney than PTH labelled with 125I alone, but the opposite was found in the degradation by the liver. Isolated intact kidney cells degraded PTH less efficiently than the homogenate, but the isolated intact liver cells degraded PTH more efficiently than the homogenate, indicating the prominence of an intracellular mechanism of degradation in the kidney and an extracellular mechanism in the liver.