Induction of spermiation in anurans by mammalian pituitary gonadotropins and their subunits

Tests with highly purified ovine FSH and LH in three species of anurans show that the spermiation response in these amphibia does not discriminate between the two pituitary gonadotropins: FSH and LH are essentially equipotent. Similar results are obtained with both hypophysectomized and intact frogs. Less purified gonadotropin preparations (NIH) give more variable results: LH is considerably more potent than FSH in Rana pipiens, but FSH is about twice as potent as LH in Hyla regilla and Eleutherodactylus coqui. There is a slight synergism between FSH and LH. However, the use of trypsin to inactivate LH and the use of antiserum to block FSH confirmed that the activity of each purified gonadotropin is an intrinsic property of the molecule. The relative potencies of the highly purified gonadotropin preparations in the anuran spermiation test differed markedly from those observed with the same preparations in mammalian and reptilian assays. In anurans, the relative potency of purified LH was about 20 times greater than in other systems, whereas, the relative potency of the highly purified FSH was only about $\text{1}\text{5}$ that observed in the other tests.The two individual subunits of LH had little activity in the frogs (ca. 2.5% of LH) and there was slight difference in their potencies. In contrast the β subunit of FSH was relatively potent (about 25% of native FSH), but the α subunit was inactive (<3%). In all three species of anuran, a crude extract of anuran (bullfrog, R. catesbeiana) pituitary glands was as potent as the most active purified mammalian hormone.