THE HORMONE DEPENDENCE OF EXPERIMENTALLY INDUCED GLIOMAS IN THE RAT

Pellets of 3,4-benzpyrene were implanted into the brains of groups of male and female rats. Animals from each of these groups were castrated or ovariectomized, and of these animals half the males and half the females received subcutaneous implants of testosterone. The position of the carcinogenic pellet in the brain was carefully controlled so that it impinged on the subependymal plate of the left lateral ventricle. A high proportion of glial tumours were produced in normal animals and it was found that deaths from cerebral tumour occurred earlier in males. Castration significantly reduced the time-related tumour incidence, and this was not reversed by testosterone. In ovariectomized females tuinour incidence was unmodified by testosterone and deaths from glioma apparently occurred later than in hormonally normal females. The implications from these results are that glial tumours are not dependent on testosterone as previously suggested. Alternative mechanisms for the sex differentiation incidence are discussed.