Tissue glycogen and blood glucose and fructose levels in the pig fetus during the second half of gestation.

Tissue glycogen levels in the liver, cardiac ventricle, lung, thigh muscle, kidney and placenta were determined in pig fetuses of 60-112 days gestational age. Liver glycogen levels increased earlier in gestation than suggested by previous reports although the maximum rate of deposition occurred between 100 and 107 days. The time of deposition of muscle glycogen was similar to that of the liver. Lung glycogen levels peaked between 70 and 90 days but then fell rapidly in late gestation. Cardiac levels were similar at all ages studied. Blood fructose levels were high in younger fetuses but levels were lower in older fetuses and were falling rapidly between 107 and 112 days. Maternal blood contained only traces of fructose. Fetal blood glucose levels were lower than maternal levels and appeared to be more closely related to maternal levels than to the gestational age of the fetuses.