Does a short-term draining of bile duct affect the plasma thyroxine level in rats?

In three groups of male rats weighing about 350 g and fed normal pelleted diet the left femoral artery and vein were cannulated under pentobarbiturate anesthesia and in samples of plasma obtained between 0 and 6 h after the injection of heparin the level of thyroxine (T4) was measured with the aid of specific radioimmunoassay. In addition, in Group A (22 animals) and C (17 animals) also the bile duct was cannulated and the total bile was collected into a flask for the same period. In addition, the animals of a Group C were thyroidectomized by electrocoagulation immediately before "O h". The Group B consisted of 18 sham-operated animals in which, in addition to the cannulation of blood vessels, only laparotomy and separation of bile duct without cannulation were made. In all groups a linear decline of plasma T4 level was found corresponding to a half-life of about 11 h. Since there were no significant differences in the slope of regression line between groups, it was concluded that the period of draining bile duct for 6 h was presumably too short to interfere significantly with the absorption of T4 in lower intestine and ileum and that the uniform decline of T4 level in plasma in all groups was presumably due to the effect of pentobarbiturate.