Properties of follicle-stimulating hormone receptors and changes during annual breeding cycle in the testis of short-tailed bandicoot rat, Nesokia indica

Some properties and seasonal changes of follicle-stimulating hormone (FSH) receptors in the testis of short-tailed bandicoot rat, Nesokia indica, were studied. The binding of FSH was highly specific for mammalian FSHs and located primarily in the testis. The Scatchard plot analyses of the binding of FSH to the testicular preparations of N. indica showed straight lines similar to those of albino Wistar rats, suggesting the presence of a single class of FSH-binding sites. The mean dissociation constants (K_ds) for FSH receptors of N. indica were 1.416 (0.964 - 2.667, 95% confidence interval) nM in December, 1986; 1.348 (0.885 - 2.849) nM in April, 1987; and 3.039 (1.678 - 16.127) nM in August to October, 1987. No significant differences were found among the three groups, but they were all significantly greater than those in Wistar rats. The FSH binding per unit weight of tissue during nonbreeding phase (June, 1987) was lower than those during other phases (December, 1986; April and August-October, 1987). Calculated numbers of FSH-binding sites showed no statistically significant differences among the latter three phases. In June preparations the number of binding sites was not determined due to their extremely low binding capacity.