Testosterone levels in the blood plasma of male chicken-pheasant hybrids.

Testosterone levels in the blood plasma of sterile male chicken-pheasant hybrids were compared with plasma testosterone levels of roosters and male pheasants, using radioimmunoassay. Mean values of testosterone in the roosters, male pheasants and chicken-pheasant hybrids during spring were 155.47 +/- 4.03, 24.29 +/- 1.55 and 0.68 +/- 0.05 ng./100 ml., respectively and the corresponding values for winter were 88.88 +/- 4.10, 0.61 +/- 0.04 and 0.76 +/- 0.07 ng./100 ml. The pheasant testes were inactive in winter but active in spring whereas the hybrid testes were inactive in winter and spring unlike those of roosters which were active during these seasons. The low levels of testosterone in hybrids during both seasons could be attributed to the impairment of steroid biosynthetic activity of the Leydig cells and may be causally related to the absence of secondary sexual characteristics and the interruption of spermatogenesis in chicken-pheasant hybrids.