Peripheral Metabolism of Intact Parathyroid Hormone: ROLE OF LIVER AND KIDNEY AND THE EFFECT OF CHRONIC RENAL FAILURE

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RESUMO

The plasma disappearance rate (metabolic clearance rate) of administered intact parathyroid hormone (intact PTH) was analyzed in awake dogs with indwelling hepatic and renal vein catheters. The metabolic clearance rate (MCR) of intact PTH was found to be very rapid, 21.6 ± 3.1 ml/min per kg in 11 normal dogs. The liver accounted for the greatest fraction of the MCR of intact PTH (61 ± 4%) by virtue of an arterial minus venous (a - v) difference across the liver of 45 ± 3%. The renal uptake of intact PTH accounted for 31 ± 3% of the MCR of intact PTH. The renal a - v difference for intact PTH of 29 ± 2% was significantly greater than the filtration fraction indicating renal uptake of intact PTH at sites independent of glomerular filtration. Together, the hepatic and renal clearances of intact PTH accounted for all but a small fraction of the MCR of intact PTH. The MCR of intact PTH, rendered biologically inactive by oxidation, was markedly decreased to 8.8 ± 1 ml/min per kg. The a - v difference of oxidized intact PTH was reduced both in the liver and kidney. These data suggested that the high uptake rates of intact PTH are dependent, at least in part, upon sites recognizing only biologically active PTH.

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