Effects of immunologically induced growth hormone deficiency on myelinogenesis in developing rat cerebrum.

Chronic deficiency of growth hormone was produced in rats by injecting highly specific antibodies against rat somatotropin during the first week of postnatal life. Antisera were prepared by immunizing adult rhesus monkeys with purified rat growth hormone. The rate of body and brain growth was significantly decreased when compared with controls injected with nonimmune serum, and 50-day-old animals showed a profound and apparently specific endocrine deficiency of pituitary growth hormone as measured by bioassay. Defective cerebral maturation was evidenced by a 70 to 80 percent decrease of myelin lipids, a 65 percent reduction of deoxyribonucleic acid, and a small but significant decline in ribonucleic acid. An abnormal accumulation of undifferentiated glia was seen in the subependymal zone in association with decreased amounts of stainable myelin in subcortical white matter. The data suggest that pituitary growth hormone and/or its secondarily induced trophic factor, somatomedin B, influences the maturation of neural cells by regulating the replication of glia and the subsequent differentiation of oligodendrocytes to form myelin.