Identification and function of the growth hormone gene in Rongjiang pig of China / 生理学报

Growth of animal is largely regulated by growth hormone (GH). In this study, the GH gene was isolated and cloned from the genomic DNA library from Rongjiang pig, a Chinese local swine, using polymerase chain reaction technique. The complete nucleotide sequence of a 1.903 kb genomic fragment containing Rongjiang swine GH gene has been determined. The GH gene contained five exons and four introns similar to the GH genes of other mammalians and exhibited 97%~99% identity to the GH genes of the four western meat-type breeds and nine Chinese local pigs. Polymorphism of GH genes was analyzed by using the restriction enzymes Dde I, Nar I and BsmN I in four western meat-type breeds and ten Chinese local pigs. Five polymorphic restriction sites, with Dde I at the base 622 (G/A) in exon 2 and 274 (T/C) in 5o-flank, with Nar I at 631 (G/A) in exon 2, and with BsmN I at the base 841 (T/C) in intron 2 and 1358 (A/G) in exon 4, were identified. The polymorphic restriction site at 1358 (A/G) leaded to the GH mature protein of Rongjiang pig differing from that of four western meat-type breeds and eight Chinese local breeds at the residue Val108 substituted by Ile108. According to the crystal structure of human GH mature protein, this Ile108 substitution might result in a lower affinity of GH for its receptor in Rongjiang breed.

Stimulatory effects of gonadotropin-releasing hormone and dopamine on growth hormone release and growth hormone mRNA expression in Epinephelus coioides / 生理学报

Gonadotropin-releasing hormone (GnRH) and dopamine (DA) can stimulate growth hormone (GH) release, but their effects on GH mRNA synthesis are controversial and deficient in fish. Orange-spotted grouper (Epinephelus coioides) is a hermaphroditic marine fish with sex reversal. Few data are available concerning the regulation of GH in grouper. In the present study, the effects of GnRH and DA on GH release and GH mRNA expression were determined using pituitary fragments of orange-spotted grouper under static culture conditions. After incubation from 1 h to 24 h, salmon GnRH (sGnRH, 100 nmol/L) stimulated the release of GH and increased the level of GH mRNA time-dependently. The minimum duration of sGnRH effect was 1 h. Both of sGnRH and mammalian GnRH (mGnRH) augmented the release of GH and the level of GH mRNA in a dose-dependent manner. The potency of sGnRH on both GH release and GH mRNA level was more pronounced than that of mGnRH. The effects of 1 micromol/L APO (Apomorphine), an agonist of D(1)/ D(2) dopamine receptors, significantly stimulated GH release and GH mRNA synthesis after incubation for 12 h. APO stimulated GH release and GH mRNA abundance in a dose-dependent manner. These results demonstrate that both GnRH and DA directly stimulate GH release and GH mRNA expression at the pituitary level, the actions of GnRH are more potent than that of DA in orange-spotted grouper.