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Title: BREED DIFFERENCES IN EXPRESSION OF INHIBIN/ACTIVIN SUBUNITS IN PORCINE ANTERIOR PITUITARY GLANDS

Author
item Li, Ming
item MACDONALD, GORDON - UMDNJ, PISCATAWAY, NJ
item Ford, Johny

Submitted to: Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Meishan boars secrete greater amounts of follicle stimulating hormone (FSH) than boars of other breeds within the United States. The Meishan breed is noted for its high litter size; therefore, we sought to learn the basis for greater FSH secretion in males of this breed to determine if there is a relationship between litter size in females and FSH secretion in males. We eevaluated expression of a number of genes whose products are potential regulators of FSH synthesis and secretion. Of these, inhibin/activin beta- B subunit was the only one that correlated with FSH secretion. This information is essential for the design of subsequent studies.

Technical Abstract: Chinese Meishan boars have remarkably greater plasma FSH concentrations than contemporary White Composite boars, but this difference does not occur in females of these breeds. The basis for elevated FSH secretion in Meishan boars is unknown. In order to examine and understand this disparity, we studied expression differences of the follistatin gene, and of the alpha-, betaA- and betaB-subunits of inhibin/activin in porcine anterior pituitary glands using semi-quantitative RT-PCR technique. We found that betaB-subunit gene is more highly expressed in pituitaries of Meishan boars than in those of White Composites, but expression of this gene was similar in females of these breeds. No differences were detected for other genes screened in this study except that the alpha-subunit could not be detected in pituitaries of either breed. These observations were confirmed by RNase protection assays. Additionally, we extended our studies to ovarian follicles collected at defined stages of development. In contrast to observations in pituitaries, alpha-subunit was highly expressed in follicles. Expression of betaB gene decreased in concert with alpha- and betaA-subunits as follicles approached ovulation. From these observations, we conclude that betaA expression predominates in porcine ovarian follicles; whereas betaB expression is more abundant in anterior pituitary glands. Furthermore, we propose that activin, a dimer of beta- subunits and a stimulator of FSH secretion, may partially be responsible for elevated plasma FSH concentrations in Meishan boars.