Excretory pattern of bile during phototherapy.

We studied the acute effects of phototherapy (PT) on bile flow and on the biliary excretion of bilirubin pigments and of bile salts in male homozygous Gunn rats (120-150 g). 13 rats received PT and 10 rats were kept in the dark. Bile was collected by cannulation of the common bile duct at hourly intervals from 1 h prior to PT till after 4 h of 'lights on'. Before treatment, all values were similar in both groups. After 4 h of lights on, mean plasma bilirubin fell from 145.3 +/- 4.3 to 99.2 +/- 2.7 mumol/l (p less than 0.01) in the PT rats, but did not change in the controls. During the lights-on period, PT rats had a significantly higher hourly bile volume, and a higher excretion of biliary bilirubin and bile salts than the controls (p less than 0.005). Over the total 4-hour lights-on period, the PT group had a higher mean output of bile than the controls (0.93 +/- 0.17 vs. 1.52 +/- 0.34 ml/4 h; p less than 0.005) and an increased excretion of bilirubin (0.08 +/- 0.016 vs. 0.148 +/- 0.01 mumol/4 h; p less than 0.005) and bile salts (35.1 +/- 3.7 vs. 55.2 +/- 12.5 mumol/4 h; p less than 0.005). The results show that PT of the Gunn rat is associated with a rise in bile flow and with an increased excretion of bile salts, in addition to an increased biliary bilirubin output.