Spermatogenesis and SRBC haemolysin formation in various inbred mouse strains treated with cyproterone acetate.

The synthetic steroid antiandrogen cyproterone acetate (CA) was administered subcutaneously to adult male mice of the inbred strains B10, B10.D2, B10.BR and C57BL/6 either as a single dose of 1 mg or as 10 daily doses of 0.5 mg. At 48 h after a single dose of CA, the thymus and spleen weights were markedly reduced and the morphology of the thymus was changed (depletion of cortex lymphocytes) in some strains. At 6 h and at 12 days after the 10th dose of CA, thymuses in males of all strains were markedly diminished with a histologically apparent involution affecting the cortex, as well as the medulla and reticuloepithelial tissue. Spleen weights in males of some strains were also significantly lower. SRBC haemolysin titres at 12 days after the 10th dose and spermatogenesis at 6 h and at 12 days after the 10th dose were significantly decreased in males of all strains; in none of the males was sterility produced by the CA doses used, however, Indications of the strain differences could only be seen in the onset and duration of the damage to the spleen and the corresponding decrease in haemolysin formation. The importance of the consequences of short-term administration of CA is discussed in terms of potential risks for long-term administration of CA in the regulation of male fertility.