Substrate concentration changes during pregnancy in the conscious rat.

Weight gain, food intake and blood metabolite concentrations were investigated in conscious pregnant and non-pregnant rats. A silastic catheter was inserted under light diethyl ether anaesthesia into the carotid artery. Surgery did not significantly affect the weight gain or food intake in pregnant and non-pregnant rats compared with non-operated females. Blood glucose concentration, which was constant during the last half of pregnancy, was 1.4-fold lower than in non-pregnant rats. Blood lactate and pyruvate concentrations were similar in non-pregnant and in pregnant animals until 16.5 days of gestation. Then blood lactate concentration was increased by 50% between 16.5 days of gestation and term, whereas in the same period of pregnancy, blood pyruvate concentration was unchanged. Blood alanine concentration was increased by 150% from 13.5 days of gestation to term. Plasma non-esterified fatty acids concentration increased progressively during the second half of pregnancy to reach values 2-fold higher than in non-pregnant rats. Blood ketone bodies concentrations were unchanged during pregnancy and similar to those observed in non-pregnant animals.