DIFFERENTIAL EXPRESSION PATTERN OF INHIBIN ALPHA AND BETA-A SUBUNITS IN THE OVARIES OF POSTNATAL AND PREPUBERTAL LAMBS

The aim of the present study was to characterize gene and protein expr ession of follistatin, inhibin alpha (alpha) and inhibin beta A (beta A) subunits in the ovaries of postnatal (3-week-old) and prepubertal ( 14 and 20-25-week-old) lambs. Northern blot analysis revealed the pres ence of two alpha and two beta A mRNAs. In postnatal ovary the alpha 1 .2-kb transcript was abundant, its amount gradually falling, while the 2.0-kb mRNA increased and became a major band at 20-25 weeks. Both be ta A mRNAs, 4.5 kb and 6.0-7.5 kb, were weakly expressed in postnatal ovary, but whereas the 4.5-kb mRNA expression remained at a low level, that of the 6.0-7.5 kb mRNA increased about five fold in prepubertal ovary. The ratio of total ct mRNAs to the dominant beta A form (6.0-7. 5 kb) varied from 1.27 at 3 weeks to 0.33 at 20-25 weeks of age. One m ajor follistatin mRNA of 2.5-3.6 kb was recognized and was constitutiv ely expressed during ovarian growth, Several molecular-mass forms of o r and beta A subunits with different compositions were seen in prepube rtal compared with postnatal ovaries, the latter exhibiting more activ e follicular growth. In summary, ovine ovaries undergo distinct change s early in life, both morphological and functional, and show a changin g pattern of inhibin subunit expression.