Pituitary relationship of gonadotropins and messenger ribonucleic acid for gonadotropin subunits in white composite and Meishan boars.

Two experiments were conducted to compare amounts of mRNAs for gonadotropin subunits in two breeds of pigs that are genetically distinct with respect to litter size : the Chinese Meishan and the white composite (a composite of four European white breeds : Yorkshire, Landrace, large white, and Chester white). In experiment 1, pituitaries were collected from mature Meishan (n = 5) and white composite (n = 6) boars. In experiment 2, boars were assigned to three groups according to peripheral concentrations of FSH : white composite (∼100 ng/ml ; n = 8), Meishan with low FSH ( 750 ng/ml ; n = 7). Within each of the three groups, five males were castrated. Two months after castration, pituitaries were collected from castrates and from eight contemporary boars for comparison purposes. Concentrations of FSH and LH were measured in half of each pituitary by RIA. RNA was isolated from the other half of each pituitary, applied to Northern and slot blots, and hybridized with cDNA probes for bovine α, LHβ, or FSHβ subunits. In experiment 1, pituitary concentrations of FSH (μg FSH/mg pituitary) were greater (p 0.05) between castrated and intact animals. Meishan males with high FSH had greater (p < 0.05) amounts of mRNA for all three gonadotropin subunits than did white composite males. From these results we suggest that greater levels of gonadotropins in the circulation of Meishan boars result, in part, from increased amounts of mRNA for gonadotropin subunits as compared with those in the white composite breed of boars.