二,三の放射性同位元素による肝臓排泄機能の研究

第1報放射性物質の正常胆汁内排泄

抄録

In order to elucidate the mechanism and physiological significance of biliary excretion, three radioactive substances, Na₂ HP³² O₄, Co⁶⁰ C1₂ and Co⁶⁰-vitamin B₁₂, were given to rabbits and the biliary excretion was compared with blood concentration and urinary excretion. These substances were chosen because of their differences in ionization and nutritional value.
1) P³² excretion: Biliary excretion of P³² following the intramuscular administration of Na₂ HP³² O₄ reached a maximum two hours after the injection, whereas the peak of radioactivity in the blood and urine came within 30 minutes and 1 hour, respectively. When administered intraperitoneally, the biliary radioactivity peak was lower and delayed, appering at 3 to 4 hours. The radioactivity in the blood was highest at 30 minutes and that in the urine reached a maximum at 2 hours following the intraperitoneal injection. The biliary excretion curve showed a gradual decline from the peak in both cases.
The concentrations of P³² following oral administration were low both in blood and bile at one hour, but the biliary concentration exceeded that of blood at 6 hours when it was maximum.
2) Co⁶⁰ C1₂ excretion: The biliary excretion of Co⁶⁰ after intramuscular injection of its chloride was much smaller and delayed, with a peak at 3 to 4 hours, than in the case of P³². The greater portion of the injected amount was excreted into the urine in 2 hours, making 6 hours excretion 95% of the total dose. This figure is in a marked contrast with 18% in the case of P³². The biliary excretion rate was maintained for 24 hours. Following intraperitoneal injection the radioactivity in bile reached a maximum within 3 to 5 hours with little excretion in early hours. The blood concentration were low and gradually increased to reach the peak in 4 hours. The urinary excretion pattern resembled that of intramuscular administration.
3) Co⁶⁰-vitamin B₁₂: The appearance in bile of Co⁶⁰ B₁₂ administered intravenously was gradual with low concentrations at the beginning to reach the peak in 3 to 4 hours, although the blood concentrations were highest immediately after injection. There was a corresponding time lag in biliary excretion. The concentrations in blood and bile decreased gradually. The urinary excretion increased sharply in 2 hours and then decreased rapidly again. The excretion pattern in bile following both subcutaneous and intramuscular administrations was the same as that of intravenous injection for lower radioactivity in bile.
The data seem to indicate that the biliary excretion reflects the metabolic behavior of administered substances and constitutes an extrarenal excretion route.