Effects of mammalian and nonmammalian gonadotropins on androgen production by minced rabbit testis.

Androgen production by minced testis from adult rabbits was measured in response to a variety of FSHs and LH5 from eutherian (sheep, rat, rabbit) and metatherian (kangaroo) mammals, a bird (turkey), reptiles (turtle, alligator) and an amphibian (frog). LHs from all three eutherian species were highly potent and produced clear stimulation at doses below 50 ng/ml; relative potencies in the rabbit were consistent with estimates from OAAD assay, but an anuran ovulation assay indicated considerable differences in potency among these three preparations. LH from the kangaroo had only about 4 percent the activity of the eutherian LHs in the rabbit testis. Potencies of mammalian (rat and ovine) FSHs were only a small fraction of the LHs (<1 percent); inactivation of ovine FSH by an LH-antiserum indicated that this low level of activity was due to residual LH contamination. Amphibian, reptilian and avian hormones were active in the rabbit testis, but a sharp dichotomy in potency was evident between these and all mammalian hormones. Nonmammalian hormones stimulated androgen production (with comparable ratios of testosterone and dihydrotestosterone), and maximal levels of androgen produced were the same or greater than obtained with mammalian preparations. However, nonmammalian hormones were consistently three to four orders of magnitude less potent than the eutherian LH5. Furthermore, in several tests, nonmammalian FSHs were also active in the minced rabbit testis at levels (20-110 percent of homologous LH) that could not be readily attributed to LH contamination. Comparisons with relative potencies for the same preparations in an anuran ovulation assay confirm that pronounced phylogenetic specificity underlies the differences in potencies between mammalian and nonmammalian gonadotropins.