Hormonal control of hepatic bilirubin transport and conjugation.

GARTNER, LAWRENCE M., AND IRWIN M. ARIAS. Hormonal control of hepatic bilirubin transport and conjugation. Am. J. Physiol. 222(5): 1091-1099. 1972. -The role of the pituitary and thyroid glands in the regulation of hepatic transport and metabolism of bilirubin in Sprague-Dawley rats was investigated with continuous bilirubin infusion and bile collection for estimation of cumulative hepatic uptake and maximal hepatic excretion of bilirubin in vivo and determination of glucuronyltransferase activity in vitro. Maximal hepatic excretion of bilirubin was Ibeduced to 40y0 of normal by 7-l 1 days after hypophysectomy and 34-36 days after thyroidectomy. Both the volume of bile secreted and the maximal concentration of bilirubin in bile were reduced. Cumulative hepatic uptake of bilirubin was probably unaffected by hypophysectomy, but may have been reduced by thyroidectomy. L-Thyroxine alone was capable of correcting the bilirubin transport defects in both groups of animals. Thyroid stimulating hormone (TSH) also corrected the defect in hypophysectomized rats. Defective glucuronyltransferase activity was observed only when ortho-aminophenol (OAP) served as the glucuronid r e eceptor in vitro. Bilirubin glucuronide formation was either normal or increased following hypophysectomy or thyroidectomy. L-Thyroxine administration returned glucuronyltransferase activity to normal. Other hormones were without effect.