Metabolic Clearance and Secretion Rates of Porcine Growth Hormone in Genetically Lean and Obese Swine

Abstract

The metabolic clearance rate (MCR) and the secretion rate (SR) of porcine growth hormone (pGH) were examined in swine rendered genetically either lean or obese after 18 generations of selection for or against backfat thickness. At 15 wk of age (when the muscle:fat ratio was greater than 1) the mean half-life (t1/2), MCR, and SR, for the obese, control and lean swine were: t1/2 = 7.4, 8.9 and 9.8 min; MCR = 341, 279 and 158 ml/min; SR = 907, 802 and 520 ng/min, respectively. At 90 kg body weight (when muscle:fat ratio was less than 1, and the age was about 30 wk) the data for obese, control and lean swine were: t1/2 = 11.3, 12.0 and 11.7 min; MCR = 305, 280 and 336 ml/min; SR = 535, 626 and 932 ng/min, respectively. The t1/2, MCR and SR were not significantly different among the obese, control and lean swine at either 15 wk or 90 kg body weight. Comparing the 2 stages of development, the younger swine (15 wk of age) had a shorter t1/2 (P < .01), and secreted and cleared more pGH on a per kg body weight basis (P < .05) than the older swine (90 kg body weight, about 30 wk of age). The results suggest that the selection of swine for either leanness or fatness for 18 generations did not alter the MCR and SR of pGH. The differences observed between the younger and older swine suggest that GH is cleared at a more rapid rate and more GH is available per unit of mass in the younger animals.