PROLACTIN AND GROWTH-HORMONE CLEARANCE IN NEONATAL BOARS

The pharmacokinetics of prolactin (PRL) and growth hormone (GH) are no t known in neonatal pigs. In this study, six boars, ages 13 and 26 d, were used to determine metabolic clearance rate (MCR), half-life (t1/2 ), and volume of distribution (Vd) of immunoreactive porcine PRL (ipPR L) and immunoreactive porcine GH (ipGH). Blood samples were collected through indwelling jugular catheters at 0, 1, 2.5, 5, 10, 15, 30, 45, and 60 min after a 20 ng/g of BW (per hormone) cocktail of porcine PRL and GH. Analysis of the ipPRL disappearance curves indicated an appar ent MCR of 13.79 +/- 2.45 and 23.79 +/- 4.10 mL/min for boars at 13 an d 26 d of age, respectively (P = .0008). The t1/2 of ipPRL did not dif fer between ages (P =.9201). The apparent MCR of ipGH at 13 and 26 d w ere 10.60 +/- 2.09 and 27.30 +/- 4.55 mL/min, respectively, and this d ifference was still evident after adjustment for BW (P = .0465). The i pGH t1/2 decreased with age (P = .0232), 21.32 +/- 2.55 vs 13.57 +/- 3 .35 min for 13 and 26 d, respectively. The apparent distribution volum e for ipPRL was higher than that for ipGH at both ages (P = .0021). Wi thin each age, the apparent MCR of ipGH and ipPRL did not differ signi ficantly. These data represent the first clearance measures reported f or ipPRL and ipGH in neonatal pigs and indicate that under the conditi ons of this study the apparent MCR of ipPRL and ipGH are similar but c hange significantly during early development.