Taurine in developing rat brain: subcellular distribution and association with synaptic vesicles of [35S]taurine in maternal, fetal and neonatal rat brain

— The concentration of taurine in the brain of the fetus in several species is higher than that found in the mature animal. In order to explore the functional significance of this, we have studied the subcellular distribution of taurine and [35S]taurine in the brain of the mother, the fetus and the neonate after [35S]taurine was administered to pregnant rats. In maternal brain, the distribution of taurine and of radioactivity (all of which was recovered from brain as taurine) in the subcellular fractions of maternal brain were essentially identical and were recovered primarily in two fractions (72% taurine, 71% [35S]taurine was soluble, S3; 16% and 17%, respectively, was in the crude mitochondrial and synaptosomal fraction, P2). After further fractionation of P2, most of the taurine and [35S]taurine were in the cytoplasmic, O, and the synaptosomal, B, fractions. In the neonatal brain, shortly after birth there was a decrease in taurine and [35S]taurine recovered in the supernatant fraction, S3, accompanied by an increase in the percentage of taurine and [35S]taurine recovered in the crude mitochondrial fraction. A small percentage of taurine and [35S]taurine was consistently recovered in the synaptic vesicle fraction. Fractionation of the synaptic vesicles on a gel column separated the vesicle bound taurine completely from the free taurine: approx 1% of the taurine in the synaptic vesicle fraction was eluted with vesicles and could not be released by hypo-osmotic shock. The pattern of development in subcellular fractions of neonatal rat brain labelled with [35S]taurine via intraperitoneal injections of the pregnant mother may be an indication of maturation or protection of putative taurinergic nerve endings.