Characterization of glucagon receptors in liver membranes and isolated hepatocytes during rat ontogenic development.

We studied the functional properties of hepatic glucagon receptors during rat development. Glucagon binding to liver membranes and isolated hepatocytes was significantly less in foetuses and weaning rats than in adult animals, reflecting changes in the number of receptors rather than any change in receptor affinity for the hormone. After correcting for the smaller surface area of foetal hepatocytes, glucagon receptor concentrations were still lower in foetuses than in adult rats. The time courses of glucagon association to liver membranes and of glucagon receptor degradation of prenatal and postnatal rats were similar, while inactivation of glucagon by liver membranes was significantly lower in foetal than in adult rats. Also, glucagon-stimulated production of cAMP was smaller in younger rats. These findings suggest that, according to several criteria, glucagon receptors in the foetus are functionally normal and their delayed development may be important for the metabolic processes occurring during the perinatal age.