PARATHYROID HORMONE-RELATED PROTEIN IN NEONATAL AND REPRODUCTIVE GOATS DETERMINED BY A SENSITIVE TIME-RESOLVED IMMUNOFLUOROMETRIC ASSAY

Objective: High concentrations of parathyroid hormone-related protein (PTHrP) have been found in goat milli but it is not known whether it c an enter the circulation of the neonate. In this study we have develop ed a sensitive two-site lanthanide immunofluorometric assay (IFMA) usi ng dissociation and enhancement time-resolved fluorometry to address t his question, Method: Affinity-purified anti-PTHrP 38-67 raised in rab bit was biotinylated and immobilized in streptavidin-coated microtitra tion wells as a 'capture' antibody, As a signal, affinity-purified ant i-PTHrP 1-34, raised in sheep, was labeled with an europium chelate, A sensitivity of 0.3 pmol/l was achieved. PTHrP levels were determined in the plasma of eleven neonatal, seven parturient and six non-pregnan t, non-lactating goats as well as in goat milk. Results: The circulati ng PTHrP levels (mean+/-S.D.) were significantly increased at day 1 (6 .1 +/- 1.7 pmol/l; P < 0.01) and day 3 (3.5 +/- 0.6 pmol/l: P < 0.05) after birth in the male kids (n = 8) bottle-fed with milli from the da ms, compared with before (2.2 +/- 0.7 pmol/l) and 30 min after (2.0 +/ - 0.6 pmol/l) the first feeding and 14 days (2.4 +/- 0.8 pmol/l) later . In the female kids (n = 3) fed with formula there was no such increa se and the concentrations remained between 1.6-1.9 pmol/l. In the part urient goats the mean+/-S.D. PTHrP levels before, during and after par turition were 2.9 +/- 1.7, 4.2 +/- 2.4 and 3.7 +/- 2.2 pmol/l respecti vely (n = 7) which demonstrated that plasma PTHrP was higher during an d after parturition in comparison with before (P < 0.05). The levels i n non-pregnant, non-lactating goats were 3.3 +/- 1.5 pmol/l (n = 6). P THrP levels in goat milk were in the nanomolar range and were highest in the colostrum. Conclusions: A significant increase of plasma PTHrP was observed in goat kids fed with milk from their dams and this incre ase was not found in kids fed with formula, Plasma PTHrP was also incr eased during parturition.