Abstract
In hypophysectomized (hypox) or thyroidectomized (thyrox) rats, the hepatic capacity to excrete bilirubin decreased progressively, reaching the maximal reduction, 40 % of normal, 7 days post-hypophysectomy and 18 to 25 days post-thyroidectomy. Both the volume of bile secreted and the concentration of bilirubin in bile were reduced. Hepatic uptake of bilirubin in vivo was unaffected by hypophysectomy but was reduced to 64 % of normal by thyroidectomy. Neither hypophysectomy nor thyroidectomy affected bilirubin glucuronide formation by liver homogenate in vitro. In hypox rats, the excretory defect was corrected after 6 days treatment with porcine growth hormone (2.0 mg/day) or thyroxine (1.25, 2.5 or 10.0 μg/day). In thyrox rats the excretory defect was corrected after 6 days treatment with thyroxine (2.5 or 5.0 μg/day). Treatment of thyrox rats with porcine growth hormone (2.0 mg/day/6 days) restored hepatic excretory capacity to 71 % of normal.
Although neither hypophysectomy nor thyroidectomy altered hepatic glucuronyl transfereas activity in vitro when bilirubin served as glucuronide acceptor, when o-aminophenol (OAP) served as glucuronide acceptor hepatic glucuronyl transferase activity declined gradually to 25 % of normal 7 days post-hypophysectomy and 18 days post-thyroidectomy. In hypox rats, the OAP conjugation defect was corrected after 22 days of thyroxine administration (10.0 μg/day), whereas 6 days treatment with eithergrowth hormone or thyroxine failed to correct the OAP conjugation defect.
These studies reveal that growth hormone and thyroxine are important in the regulation of hepatic bilirubin excretion and suggest that the synthesis of ethereal (e.g. OAP) and ester (e.g. bilirubin) glucuronides may be catalyzed by different glucuronyl transferases. (SPR)
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Gartner, L., Gluck, J. & Arias, I. 16 Hormonal Regulation of Bilirubin Excretion by Rat Liver. Pediatr Res 1, 204 (1967). https://doi.org/10.1203/00006450-196705000-00023
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DOI: https://doi.org/10.1203/00006450-196705000-00023