1996 Volume 43 Issue 4 Pages 403-410
Recent studies have demonstrated that inhibins and activins both play not only endocrine roles but also local regulatory roles in gonadotoropin secretion. There has been controversy as to the subtype of rat pituitary inhibin/activin. We studied the levels of inhibin α, βA and βB subunit mRNAs by a quantitative reverse transcription-polymerase chain reaction (RT-PCR) and the changes in their levels by adding inhibin α, βA and βB mRNA antisense oligonucleotides and inhibin A, activin A or GnRH to cultured rat anterior pituitary cells. This study demonstrated the level of 3 mRNAs to be 1.6× 10-2, 0.75 and 3.4×10-2 molecules/cell with a molar ratio of 1:50:2. A stimulatory role for activin B in FSH secretion was suggested as βB mRNA antisense oligonucleotide decreased FSH secretion. The βB mRNA level tended to be decreased by the addition of activin A, but the decrease was not statistically significant. GnRH did not affect α and βB mRNA levels when administered singly. The level of βA mRNA was not changed by any of the above treatments. In conclusion, the presence of inhibin α, βA and βB subunit mRNAs in the rat anterior pituitary with the greatest abundance of βA was demonstrated by using RT-PCR. Activin B or activin AB may play important roles in FSH secretion in an autocrine or a paracrine fashion, and activin A may play an indirect role in FSH secretion.