Duration of Response to Free and Tannated Luteinizing Hormone

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Abstract
Time studies were performed in order to determine factors involved in our previous observation that the potency of ovine luteinizing hormone (NIH-LH-Sl) is increased 4.5-fold by tannation as measured in the ventral prostate assay and decreased one half as measured in the ascorbic acid depletion assay. The studies were performed by making daily observations over a period of 4 days of the weight of the ventral prostate in hypophysectomized rats, and by determining the ovarian ascorbic acid depletion in the Parlow test rats at intervals of 4 hr for 12–24 hr after the single injection of free or of tannated NIH-LH-Sl. It was found that a single dose of tannated NIH-LH-Sl had a greater effect than an equivalent amount of free NIH-LH-Sl on the ventral prostate weight but a lesser effect in inducing ovarian ascorbic acid depletion. The ovarian ascorbic acid depletion (OAAD) assay was found to have limited use in the study of duration of response to luteinizing hormone (LH), whereas the ventral prostate weight (VPW) assay was found to be useful for this purpose. It was concluded that the greater effectiveness of tannated NIHLH- Sl in the VPW assay was due to a prolonged sojourn of the LH in the body; the lesser effectiveness of the tannated NIH-LHSl in the OAAD assay was due to the incomplete liberation of LH from the tannate. (Endocrinology76: 259, 1965)