The Effects Of Dietary Energy On Releasing Of FSH, LH, GH, Insulin, And IGF-I In Prepubertal Gilts

Three experiments were conducted to examine influences of dietaryenergy on profiles of FSH, LH, GH, insulin , and IGF-I concentrations inperipheral plasma;releasing ability of FSH, LH, and GH in suspended orserum-free mono-layer cultured pituitary cells. Twenty-four gilts ( Duroc×Landrace×Large Yorkshire) at the age of 140 days were assigned to threeenergy treatments for a period of 20 days: High energy group(HG), Middleenergy group(MG), and Low energy group(LG). Blood samples werecollected every five days, and plasma was separated by centrifuge andpreserved under -20℃ until assay for FSH, LH, GH, insulin, and IGF-Ιby RIA. On day 20 of energy treatments, gilts were slaughtered andpituitary glands were collected and subject to suspended incubation orserum-free mono-layered culture. Then suspension and culture mediumwere determined for concentrations of FSH, LH, and GH.. In experiment 1,concentrations of FSH, LH, GH, insulin, and IGF-I in peripheral plasmaincreased quickly in HG day and reduced slowly in LG till the day 10compared to those in MG, but on day 20 recovered to the basement levelbefore treatment. Concentrations of FSH, LH, GH, and IGF-I were differentsignificantly (P<0.05) on day 5 and very significantly (P<0.01) on day 10,while concentration of insulin was different very significantly (p<0.01) onday 5 and significantly (p<0.05) on day 10 between energy treatments, withthose in HG higher than those in LG. In experiment 2, concentrations ofFSH, LH, and GH in pituitary cells suspension had significant differences(P<0.05) between energy treatments, with those in HG higher than those inLG.. In experiment 3, the contents of FSH, LH, and GH in mono-layercultures of pituitary cells were very different (P<0.01) between energytreatments: HG higher than LG. Abilities of serum-free mono-layercultured pituitary cells releasing FSH, LH, and GH were influencedsignificantly by insulin, and there were differences among HG, MG, and LG(P<0.01). These results provided further evidence that metabolic hormonesare involved in regulation of the development of reproductive system inprepubertal gilts at the level of hypothalamus-pituitary-ovaries axis...