Abstract
When a pure preparation of 9-cis β-carotene was administered to rats through a stomach tube, it was absorbed and easily isomerized to all trans β-carotene in vivo. On the other hand, when synthetic all trans β-carotene was administered, 9-cis β-carotene was not found, indicating that isomerization of the all trans form to the 9-cis form does not occur in vivo. 9-cis β-Carotene and all trans β-carotene accumulated in the liver, but the levels of both carotenes in the plasma increased only transiently. However, the amounts of total β-carotene in the plasma and liver were larger in rats administered 9-cis β-carotene than in those given all trans β-carotene.
