DEVELOPMENTAL EFFECTS ON PROTEIN SYNTHESIS RATES IN REGIONS OF THE CNS IN VIVO AND IN VITRO

Abstract— Protein synthesis rates have been determined quantitatively in several regions of the nervous system of rats of various ages. The developmental changes in these regions are generally similar with a high rate maintained from several days before birth to about 4 days of age (1.9–2.1% h⁻¹). A decline in the rate ensues thereupon which continues till approx 30 days of age, whence the curve flattens though continuing slowly downward with increasing age. In the young three regions, cerebellum, pineal and pituitary, exhibit exceptionally higher rates (40–50%) than the cerebral hemispheres, pons-medulla, mid brain or cord, which all display curves of similar magnitude and shape. While the rate in the cerebellum eventually declines with age to within 10% of the rate in cerebral hemisphere, rates in the pineal and pituitary though decreasing remain far above (100%) rates in cerebral hemisphere even in adults.
The rate in vitro for slices of cerebellum follows a pattern similar to that shown previously for cerebral hemispheres: in the very young rates are 70–80% of the in vivo value but decline much more rapidly with age and in adult represent only 10–15% of the rate in vivo.
A markedly different pattern is seen in whole (unsliced) pituitaries wherein in vitro rates parallel in vivo rates with increasing age at approx 70–80% of the in vivo rate. Pineals appear to follow a similar pattern.