Assay Characteristics of Tannate Complexes of Ovine Gonadotropins

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Abstract
The discrepancy in relative potency estimates of the luteinizing-hormone (LH) activity of human pituitary gonadotropin, when measured in terms of ovine luteinizing hormone (NIH-LH-Sl) by the ventral prostate weight (VPW) assay and by the ovarian ascorbic acid depletion (OAAD) assay, was investigated by studying the LH activity of complexes of ovine follicle-stimulating hormone (NIH-FSH-Sl) and of NIH-LHSl with tannic acid. Tannates of NIH-FSH-Sl and NIH-LH-Sl were assayed by both LH assay methods. It was found that tannation increased the LH potency of both standard preparations more than 4-fold in the VPW assay and decreased the LH potency by more than half in the OAAD assay. It was concluded that chemical complexes of the ovine gonadotropin preparations can affect the assay characteristics of the LH activity, including potency estimates, thus greatly altering the index of discrimination. (Endocrinology76: 139, 1965)