Quantification of Inhibin/Activin a and bA Subunit Messenger Ribonucleic Acid by Competitive Reverse Transcription-Polymerase Chain Reaction in Chicken Granulosa Cells

The very sensitive quantitative competitive reverse transcrip-tion-polymerase chain reaction (RT-PCR) was used to investigate the expression of inhibin/activin subunits in the granulosa cells of developing ovarian follicles of the hen. Two competitors spe-cific to inhibin a and bA subunits were constructed. In one study, the expression of inhibin a and bA genes was determined in the granulosa cells of the five largest yellow follicles (F1, F2, F3, F4/5), the small yellow follicles (SYF), and the large white follicles (LWF) of a layer strain of chickens. Competitive RT-PCR for inhibin a subunit revealed 10.35 6 2.15 pg/mg total RNA in the LWF. The expression increased 40-fold in the SYF and remained at that level in the F4/5 but decreased markedly there-after up to the F1 stage. Inhibin/activin bA 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. The pattern of the mRNA for a and bA subunits in the five largest 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 subunit was significantly higher in the three largest follicles (F1, F2, F3) of the broiler breeder hens, but only in the F2 for the bA. The results suggest that inhibin a may play an important role in the recruitment and differentiation of follicles and that differences between broiler breeders and layers may have consequences at both the pituitary and ovarian levels