The specificity of inhibin bioassay using cultured pituitary cells

It has been established that the inhibition of the cellular content of FSH in cultured pituitary cells can be used as a sensitive and precise bioassay for inhibin. During studies on the inhibin content of human plasma, FSH suppression was noted to occur together with LH suppression. Further studies revealed that where combined FSH and LH suppression occurred, cytological changes in the pituitary cells suggestive of toxicity were found, indicating non-specific effects of these substances. Charcoal treatment or gel filtration of seminal plasma removed or separated the toxic substances from the inhibin activity, the latter characterized by FSH suppression parallel to the standard preparation, no LH suppression and no light-microscopic changes in pituitary cells. It is recommended that careful evaluation of all inhibin bioassay systems should be undertaken to detect substances producing non-specific effects and additional guidelines for the assessment of specificity are suggested.