Endocrine Abstracts

To elucidate biochemical evidence for follicular and oocyte maturation, inhibin-A, inhibin-B and activin-A concentrations were measured in 200 follicular fluid samples from follicles ranging from 10.2mm to 36mm in diameter. Inhibin-A concentrations varied from 7.93-436 ng/ml with a mean value was 40.1ng/ml; Inhibin B concentrations varied from 9.7-786 ng/ml with a mean value of 187.3ng/ml; Activin A concentrations varied from 1.73-267.9 ng/ml with a mean value of 40.3ng/ml. Examining concentrations and total content in individual follicles showed that these related cytokines have very different profiles with respect to follicular growth. The concentration of inhibin-A remained constant, while activin-A dropped moderately and inhibin-B decreased dramatically with follicular enlargement. However, when corrected by follicular volume, the total content of inhibin-A and activin-A increased and inhibin-B did not change with follicular development. These profiles suggest that inhibin-A is actively produced during the follicular development in order to maintain a set concentration within the enlarging follicular space. Activin-A also appears to be produced actively, possibly to maintain an inhibin/activins balance. However, inhibin-B seems not to be actively produced by granulosa cells of the enlarging follicle and thus would appear less important than inhibin-A and activin-A in follicular development and maturation.