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Bile salts in twenty six species of fish were examined to investigate the bile salt composition and the distribution of D-cysteinolic acid conjugated bile salts by high-performance liquid chromatography and/or thin-layer chromatography densitometry. Their major bile salts were cholyltaurine and/or chenodeoxycholyltaurine except for the bile salt in Japanese dace which exclusively consists of cyprinol sulfate. A considerable amount of unconjugated cholate was also found in ayu fish. D-Cysteinolic acid conjugates were detected in the bile of wild and aquacultured guelly jack, brackish goby and marbled rockfish as well as red seabream. No D-cysteinolic acid conjugates was found in biles of Japanese sardine and mackerel in spite of existences of D-cysteinolic acid in their muscle and liver.

The effect of oral administration of taurine (200-300 mg daily) on the metabolism of bile acids was studied in male guinea pigs which have predominantly glycine conjugated bile acids. The results were summarized as follows: (a) oral administration of taurine for 10 days increased taurine-conjugated bile acids and the ratio of glycine- to taurine-conjugated bile acids (G:T ratio) shifted from 3.95 to 0.19; (b) in taurine fed guinea pigs, the half-life of chenodeoxycholic acid (CDC) was about 40% shorter than that in controls and the fractional turnover rate increased by 70%; (c) the synthetic rate (mg/day/500 g body weight) of bile acids increased from 4.28 to 7.27 by taurine feeding; (d) hepatic cholesterol 7 alpha-hydroxylase activity was increased 2.4-fold by taurine feeding; (e) the total pool size of bile acids did not change significantly but the amount of lithocholic acid in the caecum and large intestine increased by about 40%; (f) neither free cholesterol nor cholesterol ester levels in liver and serum changed significantly. Results of this study suggest that changing the G:T ratio in the bile acid conjugation pattern may influence the rate of hepatic bile acid synthesis.

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Anemia caused by hemolysis occurred in coho salmon Oncorhynchus kisutch infected with the erythrocytic inclusion body syndrome (EIBS) virus. Bilirubin levels were significantly higher in the plasma of diseased fish than in healthy fish. Hyperbilirubinemia occurred in fish infected with EIBS virus. Erythrocytic superoxide dismutase activities were induced in the diseased fish. The liver bilirubin level of diseased fish was much higher than that of control fish, while the total bile acid level in the plasma of diseased fish was much higher than in the control. The plasma astaxanthin level in the diseased fish was lower than that in the control, whereas plasma vitamin A levels of both were similar. These results suggest that excretion of bile acid decreased in the diseased fish. The accumulation of bilirubin in the liver and the disfunctional bile acid excretion indicate that secretory disorder of bilirubin occurred in the diseased fish and was one of the causes of hyperbilirubinemia observed in coho salmon infected with EIBS virus.