Testosterone sensitivity of the seminal sacs of tree sparrows (Spizella arborea) in different reproductive states.
Testosterone sensitivity of the seminal sacs of castrated tree sparrows from each of three reproductive states was evaluated by measuring the change in seminal-sac mass per unit change in the logarithm of replacement or plasma testosterone. Birds were exposed to exogenous testosterone for 38 days. Replacement doses less than 0.17 mumol or plasma concentrations less than about 0.7 nmol/l did not induce seminal-sac growth in photosensitive castrated birds held on short days, in photosensitive castrated birds transferred from short to long days, or in photorefractory castrated birds retained on long days. Higher replacement doses or plasma concentrations, however, stimulated log dose-dependent growth of the seminal sacs in castrated birds from all three reproductive states. The change in seminal-sac mass per unit change in the logarithm of the dose of replacement testosterone was less (P = 0.0495) in photosensitive castrated birds held on short days than in photosensitive castrated birds transferred to long days. A more critical test of sensitivity (i.e. the change in seminal-sac mass per unit change in the logarithm of mean plasma testosterone concentration) indicated, however, that sensitivity of the seminal sacs to testosterone is independent of reproductive state. That result, when considered in the context of the plasma testosterone profile of intact males during a simulated reproductive cycle, argues that the seminal sacs of sexually quiescent (photosensitive or photorefractory) tree sparrows are small not because of their insensitivity to androgens, but because of a deficiency of circulating androgens.
F E
FE
Wilson
D000818:Animals; D001717:Birds; D008297:Male; D009919:Orchiectomy; D012098:Reproduction; D013739:Testosterone / Q000494:pharmacology / Q000502:physiology*; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology*
D013739:Testosterone