Glucocorticoids induce corticosteroid-binding globulin biosynthesis by immature mouse liver and kidney

Marked changes in mouse corticosteroid-binding globulin (CBG) gene expression in the liver and kidney occur postnatally. To study the influence of glucocorticoids on the initiation of mouse CBG biosynthesis in these tissues during the first two weeks after birth, we administered dexamethasone (0.5 microgram/g body wt/day) to 4- and 11-day-old pups for three days. This resulted in higher serum CBG and hepatic CBG mRNA levels in animals, irrespective of their ages. Higher relative amounts of CBG mRNA in the kidneys of 14-day-old pups after three days of dexamethasone treatment co-incided with higher amounts of intact and proteolytically cleaved CGB in their urine, and both are indicative of increased CGB production by the developing renal tubules. When an additional group of 11-day-old pups (n = 4) was treated with 0.25 microgram dexamethasone/g body weight per day for five days, this also resulted in significantly higher levels of serum CBG (P < 0.01), hepatic CBG mRNA (P < 0.01) and renal CBG mRNA (P < 0.05), compared to littermates treated with the oil vehicle alone. In contrast, serum CBG levels progressively decreased in adult female mice during five days of treatment with 0.5 microgram dexamethasone/g body weight per day. Taken together, these data indicate that glucocorticoids induce murine CBG gene expression in the immature liver and kidney, and support the concept that the effects of glucocorticoids on CBG gene expression are developmentally stage-specific.