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

Chinese Meishan (MS) boars have greater plasma FSH concentrations than European White Composite boars, but this difference does not occur in females of these breeds. To understand this disparity, we studied exp ression of the follistatin gene and of genes for the inhibin/activin a lpha-, beta(A)-, and beta(B)-subunits in porcine anterior pituitary gl ands using quantitative reverse transcription-PCR and ribonuclease pro tection techniques. We found that 1) the inhibin/activin beta(A)- and beta(B)-subunits and follistatin were expressed in porcine pituitary; 2) the alpha-subunit was not detected in the porcine pituitary, but wa s highly expressed in porcine follicles; and 3) the beta(B)-subunit ge ne is more abundantly expressed (2-fold greater) in MS boar pituitarie s than in pituitaries of White Composite boars. We conclude that this is not due to a breed difference, because the expression levels of thi s gene were similar in pituitaries of females of these breeds. No bree d differences were detected for other genes screened in this study. Fr om these observations, we propose that activin B, a dimer of beta(B)-s ubunits and a stimulator of FSH secretion, may be partially responsibl e for the elevated plasma FSH concentrations in MS boars, and intrapit uitary inhibin plays no or a very minimal role.