Studies have been made on the effects of maternal fasting and alloxan-induced diabetes on fetal and maternal plasma glucose and insulin concentrations, as well as on fetal myocardial and hepatic glycogen concentrations. Maternal fasting for sixteen hours, ending seventy-two hours prior to sacrifice, had no effect on maternal glucose and insulin concentrations. Under these conditions fetal insulin and hepatic and myocardial glycogen concentrations were also unchanged; fetal plasma glucose increased [from 16±2 to 26±3 mg.'100 ml. (p<0.02]. A sixteen-hour maternal fast immediately preceding sacrifice significantly decreased maternal insulin and glucose concentrations. Fetal hepatic and myocardial glycogen levels and insulin concentrations were also decreased; fetal glucose again increased [from 35±1 to 43±1 mg.'100 ml. the fetal rat, and the importance of fetal insulin on fetal glycogen concentrations are discussed.

Maternal alloxan diabetes produced elevated glucose concentrations, unchanged insulin values, decreased hepatic glycogen and increased myocardial glycogen in the fetuses. Possible mechanisms for these findings are discussed. Fetal myocardial glucose uptake in vitro was not affected by either fasting or maternal diabetes.

The data suggest that, whereas near-term fetal rats do possess some ability to control their glucose and glycogen concentrations, manipulation of maternal nutrition by fasting or alloxan diabetes can significantly alter fetal carbohydrate metabolism.

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