CLEARANCE OF EXOGENOUS PARATHYROID HORMONE-RELATED PROTEIN IN PREGNANT, NONPREGNANT AND FETAL SHEEP, GOATS AND PIGS

In the sheep, goat and pig, radiolabelled parathyroid hormone related protein (PTHRP) and immunoreactive PTHRP(1-34) and (1-86) were rapidly cleared from the circulation. Metabolic clearance rates (MCR) were in the range of 1.25-7.5 ml/min per kg and were slightly slower than that of intact PTH in man (l0 ml/min per kg); while the mean MCR of labelled PTHRP(1-86) in fetal sheep and goats was significantly faster than that in their respective mothers (14.4 vs 4.0 ml/min per kg respectively). This may reflect increased metabolism of PTHRP by fetal tissues, e.g. the placenta. Similar rates of clearance of radiolabelled PTHRP(1-141), (1-86) and (1-34) suggest that clearance involves the amino terminus of the molecule.