Autoradiography with 14C-bilirubin in pregnant normal Wistar rats and Gunn rats with and without phenobarbital or albumin administration.

Abstract

Pregnant normal Wistar rats and Gunn rats were given 25 μCi (1 mg) 14C-bilirubin intravenously. They were killed at different intervals. Whole-body autoradiography was used to study the different pathways of bilirubin in normal rats and in Gunn rats. Numerous spots of intense blackening were seen on the autoradiographs in the area of the liver of normal rats, indicating biliary excretion of the administered isotope. In the autoradiographic picture of the Gunn rat liver more diffuse blackening was present. In the normal rat the bowels contained radioactive material shortly after the injection, whereas in Gunn rats no radioactivity was demonstrable within the lumen of the bowels; the area over the bowel wall showed intense staining suggesting some mucosal excretion of bilirubin, however. The isotope content of the renal cortex was somewhat higher than that of the medulla in all animals. In addition, the papillae of the Gunn rat kidney contained a very high level of radioactivity; crystallization of bilirubin takes place in this area. Usually there was no radioactivity in the brain or spinal cord outside the vessels. One Gunn rat with an apneic spell immediately after the injection of bilirubin has isotope deposits throughout the brain. The fetuses of normal and Gunn rats showed less radioactivity than the mother animals. The lumen of the fetal bowels was always free of radioactivity even in fetuses of normal Wistar rat mothers with large amounts of the isotope within the gut. With the aid of the stripping-film technique it was possible to demonstrate that some isotope was localized within the liver cell as soon as 30 sec after the injection. In normal Wistar rats only an intense blackening was visible over the bile capillaries and intrahepatic bile ducts in later stages of the experiments. If albumin was given in addition to 14C-bilirubin the same autoradiographic pattern was obtained. Phenobarbital pretreatment caused no autoradiographic changes.