QUANTIFICATION OF INHIBIN ACTIVIN ALPHA-SUBUNIT AND BETA(A) SUBUNIT MESSENGER-RIBONUCLEIC-ACID BY COMPETITIVE REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION IN CHICKEN GRANULOSA-CELLS DURING FOLLICULAR DEVELOPMENT/

The very sensitive quantitative competitive reverse transcription-poly merase chain reaction (RT-PCR) was used to investigate the expression of inhibin/activin subunits in the granulosa cells of developing ovari an follicles of the hen. Two competitors specific to inhibin alpha and beta(A) subunits were constructed. In one study, the expression of in hibin alpha and beta(A) genes was determined in the granulosa cells of the five largest yellow follicles (F1, F2, F3, F4/5), the small yello w follicles (SYF), and the large white follicles (LWF) of a layer stra in of chickens. Competitive RT-PCR for inhibin a subunit revealed 10.3 5 +/- 2.15 pg/mu g total RNA in the LWF. The expression increased 40-f old in the SYF and remained at that level in the F4/5 but decreased ma rkedly thereafter up to the F1 stage. Inhibin/activin beta(A) subunit was also detected in the LWF in low amounts and showed no significant increase until the F2 stage. The highest level was found in the F1. Th e pattern of the mRNA for alpha and beta(A) subunits in the five large st follicles (F1, F2, F3, F4/5) of a broiler breeder strain of chicken was compared with that in the layer strain. Expression of the a subun it was significantly higher in the three largest follicles (F1, F2, F3 ) of the broiler breeder hens, but only in the F2 for the beta(A). The results suggest that inhibin alpha may play an important role in the recruitment and differentiation of follicles and that differences betw een broiler breeders and layers may have consequences at both the pitu itary and ovarian levels.