Lactotroph and somatotroph function in piglets reared in a constant hot environment.
The present study evaluated the effect of rearing in a constant hot (32 degrees C) or cool (21 degrees C) thermal environment (TE) on lactotroph and somatotroph secretory activity in 5-wk-old barrows (castrate males) and gilts (female). Pituitary cells from seven gilts and seven barrows from each TE were cultured at a density of 250,000 cells/1 ml well and exposed to vehicle (culture medium); .1, 1, 10, or 100 nM thyrotropin-releasing hormone (TRH); or .1, 1, or 10 nM growth hormone-releasing hormone (GHRH). Post-receptor cellular stimulation was induced pharmacologically with 2 mM 8-Br-cAMP (cAMP); 100 nM phorbol myristate acetate (PMA); or 59 mM KCl. Prolactin secretion in culture was stimulated by TRH and by pharmacological compounds (p < .0001). In vitro PRL secretion was increased approximately two-fold in the hot environment (p < .02). Similarly, cellular PRL content in the hot TE was twice that in the cool TE (p < .01). The in vitro secretion of growth hormone (GH) was increased by GHRH and by pharmacological compounds (p < .0001), but was unaffected by TE (p > .5). No effects of sex (p > .3) or sex x TE interactions (p > .2) were detected in any endpoint. The results of this study demonstrate that lactotroph, but not somatotroph, secretory activity is enhanced by a constant hot TE in early postweaning pigs. This increase in secretory activity does not appear to be dependent on receptor-mediated cellular activation, but may reflect enhanced levels of cellular PRL available for release.
Matteri
R L
RL
United States Department of Agriculture, Agricultural Research Service, Animal Physiology Research Unit, University of Missouri, Columbia 65211, USA.
Becker
B A
BA
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000064:Acclimatization; D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003080:Cold Temperature; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D006358:Hot Temperature; D008297:Male; D009919:Orchiectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D011863:Radioimmunoassay; D015203:Reproducibility of Results; D013552:Swine / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D015124:8-Bromo Cyclic Adenosine Monophosphate; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D013755:Tetradecanoylphorbol Acetate