ステロイド薬剤の肝内代謝考察法に関する比較研究

抄録

It is reasonable to presume that the metabolism of the steroid hormones in the liver may play an important role in elucidating their physiologic significance.
Although there are many methods by which the intrahepatic metabolism of the steroid hormones can be evaluated, little has been reported on a method to elucidate simultaneously such dynamic factors as metabolic rate, quantities passing through the liver, structural change, conjugation and the like.
In this paper, comparative studies on the methods for the investigation of steroid hormone metabolism in the liver were carried out.
These include batch incubation, dialysis, continuous flow perfusion, portal vein injection and the “tissue column method” which was newly designed in order to search for the dynamic factors described above in a simple system, simultaneously.
In the “tissue column method” studied here, cell suspension of the rabbit liver mixed with Sephadex G 75 gel (4 : 1 in volume) was packed at the height of 4 cm in a glass column (internal diameter ; 1.5 cm).
After an isotopically labelled steroid was placed on the tissue column, this column was perfused with oxygenated extracellular fluid (pH 7.4), keeping the perfusion system at 37°C.
The perfusion was continued for 60 min. and the perfusate was collected in 5 fractions. Flow rate was kept at 2 ml/min.
When the perfusion was stopped, the cells were rapidly homogenized. The concentrations of the radioactivity in each perfusate, and in the final cells were measured. The amount of entry into the liver cells were calculated.
The compounds in the perfusate and in the cells were separated by alumina column chromatography for analyzing the metabolites.
Based on these experiments, the following conclusions were drawn ;
1) Usual methods with liver slices and homogenates can clarify only the metabolic pathway.
2) To examine the amount of entry of steroids into the liver, portal vein injection as well as the “tissue column method” are preferable to the methods of dialysis and batch incubation. It seemed probable that the entry of steroids into the liver might not be explained simply on the basis of passive transfusion.
3) Incubation of slices and homogenate are of great advantage in studying the metabolic transformation in a specific organ. However, portal vein injection as well as the “tissue column method” are much more preferable to investigate the conjugation of steroids in the liver.
4) Continuous flow perfusion reported by Elrio Gurpide is suitable to examine the metabolism and the entry of steroids in a specific organ, but it is disadvantageous for investigating the conjugation of steroids because of its low production rate of conjugated steroids.
5) The portal injection method is intricate, troublesome and expensive, but this method provides a situation similar to in vivo circumstances.
6) It is evident that despite its simplicity, the newly designed “tissue column method” is of great worth in obtaining summarized information of the entry, metabolic pathway, metabolic rate, structural change and conjugation of the steroid hormones in the liver.