Regulation of peripheral glucagon concentrations in cyclic, pregnant, and lactating rats.

In the rat, peripheral glucagon concentrations were studied throughout pregnancy and lactation. Basal glucose concentrations were decreased during late pregnancy and during lactation, but basal glucagon concentrations were not affected. Infusion of glucose (7.4 mg/min) caused an elevation of the glucose concentrations, which became lower in the course of lactation, and a suppression of the glucagon concentrations which was the same throughout pregnancy and lactation. Ingestion of 336 mg of glucose or 1 g of rat chow throughout pregnancy and lactation induced a transient increase of the glucose concentrations and a biphasic glucagon response: following a short-lasting elevation, the glucagon concentrations became suppressed. The glucagon responses to these tests did not change during pregnancy and lactation. It is concluded that the regulation of the peripheral glucagon concentration is not affected by pregnancy or lactation, and that the response of the glucagon concentration to a metabolic challenge varies with the kind of test (oral or intravenous) used.