Early adrenalectomy stimulates subsequent growth and development of the rat brain

Rats were adrenalectomized (ADX) or sham-operated (SHAM) on the 11th day of life and subsequent brain development (cerebrum and cerebellum) studied in terms of tissue weight and biochemical composition. Measured at about 65 days of age, early ADX subjects had significantly heavier brains (in terms of both wet and dry weights) than SHAMs, despite being lighter in overall body weight. Brain protein and DNA contents were elevated, as was the activity of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP), a myelin marker enzyme. Glycerol-3-phosphate dehydrogenase (GPDH), a glucocorticoid-regulated enzyme, was reduced in activity. Although both the cerebrum and cerebellum showed the growth-enhancing effects of early adrenalectomy, the DNA and CNP changes were most pronounced in the cerebrum. Finally, the effect of adrenal removal on myelinogenesis was confirmed by subcellular fractionation experiments demonstrating that more myelin could be recovered from the brains of ADX than from SHAM animals. These results are significant in terms of the influence of adrenal secretions on normal brain development and the role of GPDH in myelin lipid biosynthesis.