QUANTITATIVE RT-PCR FOR INHIBIN ACTIVIN SUBUNITS - MEASUREMENT OF RATHYPOTHALAMIC AND OVARIAN INHIBIN/ACTIVIN SUBUNIT MESSENGER-RNAS DURING THE ESTROUS-CYCLE/

Inhibins (alpha-B-A and alpha-B-B) and activins (beta(A)-beta(A), beta (A)-beta(B) and beta(B)-beta(B)) were originally isolated from ovarian follicular fluids as FSH secretion modifiers. Inhibin/activin subunit s, alpha, beta(A) and beta(B), are widely distributed in several tissu es, including gonads and brain, and inhibins and activins have been re ported to be involved in ovarian or hypothalamic functions. In this st udy, we established and employed a competitive RT-PCR assay system for rat inhibin/activin subunits by capillary electrophoresis to determin e rat hypothalamic and ovarian inhibin/activin subunit mRNA levels dur ing the estrous cycle. Linearity of standards for alpha, beta(A), and beta(B) subunit assays were between 9.01-0.3 amol, 0.003-0.09 amol and 0.002-0.02 amol of each fragment DNA as a standard, respectively. Hyp othalamic beta(A) subunit mRNA. during the estrous morning (1000 h) te nded to be increased compared with that of the proestrous evening (170 0 h), although they were not significantly different. Ovarian a subuni t mRNA levels tended to be increased during the proestrous morning (10 00 h) and were significantly increased in the proestrous evening (1700 h), compared with diestrus and estrus (P<0.05). Ovarian beta(A) subun it mRNA was also significantly higher in the proestrous evening, compa red with diestrus and estrus (P<0.05), but in the case of beta(B) subu nit mRNA there was no difference among diestrus, proestrus and estrus. We thus established a sensitive competitive RT-PCR system for the mea surement of inhibin/activin alpha, beta(A) and beta(B) subunits, and t his assay system would be helpful for the study of inhibin/activin act ion in brain and other tissues where these factors are expressed at lo w levels.