Plasma levels of cortisol and corticosteroid-binding globulin (CBG) and hepatic CBG mRNA expression in pre- and postnatal pigs

Abstract

The relationships among hepatic corticosteroid-binding globulin (CBG) mRNA expression and plasma concentrations of cortisol and CBG was evaluated in fetal pigs ( n=7–14 per age) on days 50, 70, 80, 90, and 104 of gestation and postnatal pigs ( n=8 per age) on days 1, 3, 10, 20, 30, and 40 following birth. In fetal pigs, hepatic CBG mRNA expression was highest ( P<0.01) on day 50 as compared to days 90 and 104, exhibiting an overall negative relationship ( r=−0.63; P<0.01) with estimated gestation age. Plasma porcine CBG (pCBG) concentration was correlated ( r=0.34; P<0.05) with hepatic CBG mRNA level. Plasma cortisol concentrations were not different over this same period. In postnatal pigs, hepatic CBG mRNA expression increased ( P<0.01) from days 3 to 40. The pCBG concentration increased ( P<0.01) from days 1 (6.1±3.4 μg/ml) to 10 (15.1±3.7 μg/ml), while plasma cortisol concentration remained constant. An understanding of the relation between hepatic CBG mRNA and circulating pCBG concentrations may provide insight into the mechanisms determining the bioavailability of cortisol necessary in prenatal development and the conservation of cortisol during postnatal development in the pig.