Desmosterol in rat central and peripheral nervous systems during normal and neoplastic growth

Desmosterol (5, 24-cholestadien-3beta-ol; delta 24-cholesterol; 24-dehydrocholesterol), an immediate precursor of brain cholesterol, increased in malignant intracranial tumors induced in rats by nitrosourea derivatives. The average increase in desmosterol was higher in intracerebral gliomas than in neurinomas of the trigeminal nerve. Similarly, desmosterol increased only slightly in developing normal trigeminal nerve compared to the high levels observed in developing cerebrum. The differences may have been partly related to the predominantly growing cell type, i.e., glial (central nervous system) or Schwann (peripheral nervous system) cells seen at the time of study.

Differential oncogenic effects of methylnitrosourea

We investigated differences in the oncogenic effects of methylnitrosourea (MNU) which were induced by varying dose schedules and changing administration routes. The nervous system represented the target organ when MNU was given intravenously to rats. Carcinogen by other routes resulted in decreased numbers of neurogenic tumors and the appearance of neoplasms at the injection site. Increased oral doses of MNU caused shorter survival times, a decreased incidence of neuroglial tumors, and increased numbers of thymic lymphomas and mesenchymal tumors of the nervous system. The results suggest that many tissues are susceptible to the oncogenic effects of MNU, but the degree of exposure necessary for neoplastic transformation varies.