DISTRIBUTION BETWEEN PROTEIN-BOUND AND FREE FORMS OF PLASMA-CORTISOL IN THE GILT AND FETAL PIG NEAR-TERM

Thirty-five time-dated pregnant gilts were used to document plasma lev els of total and free cortisol, corticosteroid-binding globulin (CBG) binding capacity, and percent distribution of cortisol among protein-b ound (CBG and albumin) and free forms in the fetal pig during the last 24 days ofgestation. Plasma from fetal pigs on days 110-114 of gestat ion (gestation length 114 days) had significantly higher levels of tot al cortisol (p < 0.01), percent albumin-bound and free cortisol (p < 0 .10), and free cortisol concentration (p < 0.05) compared to samples o n days 90, 100 and 105, Fetal plasma CBG binding capacity increased (p < 0.05) linearly from day 100 to 114, Fetal pigs located in the cervi cal region ofthe uterus had lower (p < 0.05) total and free cortisol a nd higher (p < 0.05) albumin and total protein concentrations compared to fetuses in the middle and oviductal regions, Total, percent free a nd free cortisol concentrations in maternal plasma on days 105-114, we re greater (p < 0.10) than that measured on days 12-100 of gestation. These results suggest that the developmental patterns of plasma cortis ol and CBG in the prenatal pig are directly related and highly similar to those of another precocious species, the sheep.