Regulation of testicular infiltration in acute lymphoblastic leukaemia of the rat.

The testis is a common site of relapse in childhood acute lymphoblastic leukaemia (ALL). In adults, testicular relapses of ALL are very rare. A similar age-difference in the frequency of the testicular infiltration exists also in the rat T-cell leukaemia. In the present investigation, the effect of various hormonal treatments and unilateral cryptorchidism on the form of testicular infiltrates by the rat T-cell leukaemia was studied. Inhibition of testicular activity by estradiol treatment (E2) of early pubertal rats injected i.p. with rat T-leukaemic lymphoblasts significantly decreased the proportion of the testis occupied by leukaemic infiltrates. The proportion of the testis occupied by leukaemic infiltrates was significantly higher in the abdominal testes of both early and late pubertal unilaterally cryptorchid rats, than in the scrotal testes of leukaemic control rats. Daily treatment of early pubertal rats with human chorionic gonadotrophin (hCG), or human menopausal gonadotrophin (hMG), did not have an effect on testicular leukaemic infiltration. These studies demonstrate that the leukaemic infiltration of the testis is influenced by the changes in the physiological activity of the testes.