The mechanisms for ascorbic acid transport were investigated in samples of human placenta obtained from normal term pregnancies. Results suggest that at very high ascorbic acid concentrations this vitamin may cross the placenta by simple diffusion. However, at lower ascorbic acid concentrations the predominant form of transport is carrier mediated and energy dependent. The energy used in the transport process can be derived from either glycolysis or oxidative phosphorylation. In addition, the transport system also requires the presence of sodium and of Na+-K+-dependent ATPase activity.
On day 20 of gestation, after ethanol feeding (27% ethanol calories, 25% protein), placental weights, DNA, RNA and water content were greater than in controls pair-fed an isocaloric diet without ethanol or those ad lib fed a pellet diet of similar composition. Rat litter size and fetal body, liver and brain weights were similar in all groups. In vivo fetal amino acid accumulation was significantly lower after alcohol exposure despite similar placental uptake. These results indicate that both placental hyperplasia and abnormal fetal amino acid uptake occur at a low alcohol dose when fetal body weight is unaffected.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.