Autoradiographic study of [35S]-cysteine and [1-14C]-cystine in pregnant and neonatal mice.

The distribution and fate of 35S from [35S]-cysteine and 14C from [1-14C]-cystine, both precursors to taurine in 17-day pregnant mice and (1-day-old) neonates were investigated by whole-body autoradiography following IV injection for the pregnant mice and IP injection for the neonates. Survival intervals were 30 min, 3 hr. In the dam, 35S and 14C were both highly incorporated into the pancreas. As very low uptake of [35S]-taurine in the pancreas was found in a previous study, it is reasonable to suggest that most radioactivity found in the pancreas represents cysteine. In maternal brain, brown fat, and myocardium, optical density and relative ratio (ODs of 35S and 14C in each tissue and organ/ODs of 35S and 14C in the blood) of 35S were significantly higher than those of 14C, assuming that most of 35S might be present as taurine in these regions. In the developing brain, 35S was found mainly in the differentiating neurons of the cortical plate, including the primordial hippocampal cell layer, and of the cerebellar cortical plate. Relative ratios of 35S in these cerebral regions were significantly higher than those of 14C, suggesting that most of 35S represents taurine.