A high-performance liquid chromatographic (HPLC) meth-od for simultaneous determination of 7-dehydrocholesterol (7-DHC), vitamin D
3 and 25-hydroxyvitamin D
3 (25-OH-D
3) in tissues of fishes was established, and using this method the tissue distribution of the sterols in lamprey (
Entosphenus japonicus), great blue shark (
Prionace glauca), skipjack (
Katsuwonus pelamis) and albacore (
Thunnus alalunga) was in-vestigated. The results are summarized in the following:
1) Although the alimentary canal, gall bladder and roe of lamprey and the alimentary canal of great blue shark contained comparatively high levels of 7-DHC (higher than 2, 000ng/wet tissue g), the other tissues of lamprey and great blue shark and all tissues of skipjack and albacore contained only low levels of 7-DHC (lower than 1, 000 ng/g). There was no significant correlation between the levels of 7-DHC and vitamin D
3. 2) The contents of 7-DHC in the skin of skipjack and albacore were only 1/1, 000 of those in the skin of rats. 3) Although the contents of vitamin D
3 in the liver of skipjack and albacore were extremely high (41, 240 and 21, 000ng/g, respectively), those in the skin were very low (454 and 257ng/g, re-spectively). 4) 25-OH-D
3 was detected in the viscera of skipjack, but the levels were not very high (lower than 150ng/g). These levels were not significantly correlated with those of vitamin D
3.
The results suggest that large quantities of vitamin D
3 in the liver of skipjack and albacore are supplied by other biosynthetic routes or by intake of vitamin D
3 rather than by photochemical biosynthesis.
View full abstract