Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/21/1999
Publication Date: N/A
Technical Abstract: Transcription of growth hormone receptor (GHR) mRNA is initiated from multiple promoters. Most GHR mRNA arise from Promoter 1 and 2 that transcribe GHR 1A and GHR 1B mRNA, respectively. The objective was to characterize the developmental expression of GHR 1A and GHR 1B mRNA in liver of castrated male pigs (Study 1) and intact male pigs treated with recombinant porcine somatotropin (rpST; Study 2). For Study 1, 24 castrated male pigs were slaughtered at one of four ages (1, 14, 28, and 42 d, n=6/age group). For Study 2, 24 intact male pigs were treated with rpST (200 ug/kg BW/d) or control beginning at 7, 28, or 63 d of age and slaughtered 14 d later (21, 42, and 77 d; n=4 pigs/treatment/age). Tissue samples were collected at slaughter for mRNA analyses. The porcine GHR 1A and GHR 1B cDNA were cloned and were 89.2% and 89.7% homologous to bovine, respectively. A ribonuclease protection assay was used to measure GHR 1A and GHR 1B mRNA. Liver expressed GHR 1A and GHR 1B mRNA, whereas muscle, uterus, and ovary expressed GHR 1B mRNA. The liver of castrated male pigs (Study 1) expressed GHR 1B mRNA at all ages and the amount of GHR 1B tended to increase (P<.10) with age. GHR 1A mRNA in the liver was not expressed until 42 d of age in castrated male pigs. The liver of intact male pigs (Study 2) expressed GHR 1A and GHR 1B mRNA by 21 d and there was an age-related increase in GHR 1A mRNA (P<.01) and GHR 1B mRNA (P<.10). Administration of rpST had no effect on expression of GHR 1A or GHR 1B mRNA. In conclusion, GHR mRNA in porcine liver was composed of at least two variants (GHR 1A and GHR 1B). The GHR 1B mRNA was found at all ages whereas GHR 1A mRNA was detected by 21 (intact male) or 42 (castrated male) d of age. Both GHR 1A and GHR 1B mRNA increased with age.