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Relationship between in vitro somatotroph function and growth in three-week-old barrows |
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| Authors: | R L Matteri W R Lamberson and D H Keisler |
| Institution: | a United States Department of Agriculture, Agricultural Research Service Animal Physiology Research Unit, Room S-143 Animal Sciences Research Center University of Missouri, Columbia, Missouri, 65211, USA b Department of Animal Science, University of Missouri, Columbia, Missouri, USA |
| Abstract: | 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 × 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. |
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