Comparative Effects of All-trans and 13-cis Retinoic Acid Administration on Serum and Liver Lipids in Rats

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Abstract
The effects of all-trans and 13-cis retinoic acid upon serum and liver lipids were investigated in Sprague-Dawley rats. Groups of rats were fed daily with 105, 210 and 315 µg/g diet of one of the retinoids for periods of up to 8 days. Other groups were injected intraperitoneally (I.P.) daily with retinoids at levels equivalent to the daily intake of rats receiving 105 or 210 µg of retinoid/g diet. All dietary concentrations of all-trans retinoic acid induced hypertriglyceridemia, however, only the highest dietary concentration of the 13-cis form caused this response. Injection of the all-trans form consistently increased serum triglycerides, while 13-cis retinoic acid did so in only one case. Retinoid-fed rats fasted for 6 hours before blood sampling demonstrated similar increases in serum triglycerides compared to their respective controls. Also, retinoid administration reduced serum retinol at all levels tested with the all-trans form appearing to be more potent. Growth and feed intake was somewhat reduced in rats receiving the highest level of all-trans retinoic acid. Liver analysis did not reveal fatty liver or alterations in phospholipid, cholesterol or vitamin A content in any groups monitored. Our previous studies have shown induction of hypertriglyceridemia when rats were fed as low as 26 µg/g diet of all-trans retinoic acid. The current studies would indicate that feeding 315 µg/g diet of the 13-cis isomer was required to elicit a similar response.