RIA determination and immunofluorescence localization of cyclic nucleotides in rainbow trout (Salmo gairdneri) testes

Using histological criteria, testicular development was divided into six stages (I-Va). The testicular amounts of 3',5'-cyclic adenosine- and guanosine monophosphate (cAMP, cGMP) were determined radioimmunologically, and their testicular distribution patterns were monitored by indirect immunofluorescence microscopy. During slow testicular growth (stages I-III), the nucleotide concentrations were high (0.62-1.2 pmol cAMP/mg, 0.17-0.24 pmol cGMP/mg). With the appearance of spermatozoa in stage IV, they fell to low levels which were maintained with some fluctuations until the end of the cycle (0.05-0.1 pmol cAMP/mg, 0.016-0.05 pmol cGMP/mg). The cAMP antiserum intensely stained spermatogonia, a portion of the spermatocytes, and spermatids. Spermatozoa showed almost no staining. Fluorescence labeling of somatic cells was observed in immature testes and during spermiation. Except for staining all spermatocytes, the same pattern was observed using the cGMP antiserum.