JBC, Vol. 250, Issue 15, 5847-5851, Aug, 1975
Ontogeny of glucocorticoid receptors in rat liver
G. Giannopoulos
Specific receptors for glucocorticoids are present in liver cytosols of rat
fetuses at least as early as the 18th day of gestation. The concentration
of the receptor begins to decline after the 20th day reaching undetectable
levels shortly before and after parturition. The receptor can be detected
again 1 to 2 hours after birth, and its levels increase markedly to higher
than adult values between the 2nd and 5th day. The reason for the failure
to detect specific hormone binding near parturition appears to be due to
occupation of binding sites by endogenous steroids rather than the absence
of the receptor. This is indicated by the demonstration of both cytoplasmic
and nuclear receptor sites in liver slices of newborn rats incubated with
labeled dexamethasone at 37 degrees. The cytoplasmic receptors of fetal and
adult liver differ in their relative affinity for cortisol and
corticosterone. The fetal receptors have a higher affinity for
corticosterone than cortisol while the reverse is true for the adult
receptors. These observations suggest either the existence of dissimilar
receptors in fetal and adult liver or the presence of more than one type of
receptor sites. It is therefore possible that subtle differences in the
nature of hepatic receptors may be partly responsible for the
maturation-dependent qualitative differences in tissue responsiveness to
glucocorticoids.
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