Relationship between in vitro somatotroph function and growth in three-week-old barrows.
The relationship between in vitro somatotroph function and growth was examined in piglets demonstrating a continuous range of growth characteristics. Twenty barrows were sacrificed at 3 weeks of age for the collection of pituitary tissue and blood. Pituitary cells from each animal were cultured and exposed to vehicle (culture medium); .1, 1, and 10 nM growth hormone-releasing hormone (GHRH); 2 mM 8-Br-cAMP (cAMP); 100 nM phorbol myristate acetate (PMA); and 59 mM KCl. All secretagogue treatments stimulated growth hormone (GH) secretion (p < .0001). Basal and stimulated GH secretion in culture, intracellular GH content (icGH), and serum insulin-like growth factor-1 (IGF-1) concentrations were all positively correlated with 3-week weight gain (p < .05). Concentrations of GH in the serum sample taken at sacrifice were not related to growth (p > .3). Intracellular GH content was correlated with in vitro GH secretion (p < .01) and serum IGF-1 concentrations (p < .001). Somatotroph function was contrasted in the 7 largest and 7 smallest piglets (large, 8.3 +/- .3 kg, n = 7; small, 4.5 +/- .2 kg, n = 7). Treatment with GHRH produced a dose-related increase in GH secretion in both experimental groups (p < .0001). No significant size x GHRH interaction was detected (p = .09), When contrasted with the small group, the large group demonstrated elevated GH secretion in culture (p < .01), icGH content (p < .001), and circulating IGF-1 (p < .001). The results of this study raise the possibility of a functional relationship between porcine somatotroph secretory activity and growth, mediated by IGF-1, which may be regulated by the quantity of GH available for release.
Matteri
R L
RL
United States Department of Agriculture, Animal Sciences Research Center, University of Missouri, Columbia 65211.
Lamberson
W R
WR
Keisler
D H
DH
D000818:Animals; D002478:Cells, Cultured; D013006:Growth Hormone / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D011863:Radioimmunoassay / Q000662:veterinary; D013223:Statistics as Topic; D013552:Swine / Q000254:growth & development* / Q000378:metabolism
D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone