Fish gonadotropin(s). I. Bioassay of salmon gonadotropin(s) in vitro with immature trout gonads.

1. The effect of salmon gonadotropin(s) (SG) on cyclic AMP (cAMP) levels in immature trout gonadal tissue of both sexes was measured by radioimmunoassay. 2. A dose-response line was obtained to SG in gonads of both male and female trout. 3. As little as 0.45 SG units (1 SG unit = 1 mug NIH-LH-S18 in the chick bioassay) significantly increased cAMP formation in the presence of 8 mM theophylline; mammalian LH, FSH, LTH, ACTH, TSH and HCG were inactive. 4. The assay for SG was investigated with respect to time of incubation and two phosphodiesterase inhibitors; some conditions for the cAMP radioimmunoassay (cAMP-RIA) were compared.