Relation between renal and hepatic excretion in drugs: VIII. Influence of triiodothyronine on maturation of phenol red excretion in rats

Abstract

Experiments were performed on 10-, 20-, and 55-day-old female rats. Administration of triiodothyronine (T3; 10 or 20 micrograms/100 g b.wt. for 3 days, once daily) was followed by a significant increase in renal phenol red excretion in 20-day-old and older rats. In 10-day-old rats there was no stimulatory effect of T3 on renal excretion of the dye. On the other hand, biliary excretion of phenol red was significantly diminished in all age groups. Surprisingly, in nephrectomized rats there was a significant increase in hepatic dye excretion in 20- and 55-day-old rats after T3. This increase in transport capacity via liver was connected with a distinct rise of bile flow. In experiments on tissue slices phenol red accumulation was investigated at different medium concentrations. In renal cortical slices there was no significant influence of T3 on specific accumulation of phenol red per 1 g organ wet weight, whereas aerobic accumulation of the dye seems to be diminished in liver tissue after T3 treatment. But in all age groups kidney weight increased significantly. Calculation of total accumulation (= specific accumulation x organ wet weight) resulted in a significantly enhanced renal transport capacity for phenol red in all age groups. In contrast, total hepatic accumulation was reduced independently of age.