Effects of subcutaneously injected graded doses of all-trans retinoic acid and all-trans retinoyl beta-glucuronide on the outcome of pregnancy in Sprague-Dawley rats.

The effects of single subcutaneous injections (s.c.) of graded doses (20, 40, 80, 160, 320, and 480 mumol/kg body weight (BW) of all-trans retinoic acid (RA) and all-trans retinoyl beta-glucuronide (RAG) on day 8.5 of gestation on the outcome of pregnancy in Sprague-Dawley rats was studied. At dose levels of 20, 40, and 80 mumol/kg BW, neither RA nor RAG showed any adverse maternal or fetal effects. However, at dose levels of 160, 320, and 480 mumol/kg, RA was found to be much more toxic than RAG to both mother and fetus. Fetuses of animals receiving a 160 mumol/kg BW dose of RA were significantly reduced in weight and length, while animals receiving the same dose of RAG had fetuses of normal size. RA doses of 320 and 480 mumol/kg BW resulted in symptoms of maternal toxicity and even death. In contrast, RAG at these high levels produced no signs of maternal toxicity. RAG doses of 320 and 480 mumol/kg BW were also less toxic to fetuses. RA doses of 320 mumol/kg BW resulted in only 8% live births, while animals treated with an equivalent amount of RAG experienced 95% live births. Animals receiving a dose of 480 mumol/kg BW of RA had no live births, but similar doses of RAG resulted in 28% live births and pups of normal size.

Comparative histologic effects of daily topical application of creams containing all-trans-retinoic acid or all-trans-retinoyl beta-glucuronide on pig skin.

The efficacy of all-trans-retinoic acid (tRA) and all-trans-retinoyl beta-glucuronide (RAG), a water-soluble metabolite of vitamin A, in the topical treatment of acne is comparable. However, whereas 3.3 mM tRA shows side effects, 3.3 mM RAG does not. To assess the relative toxic and histologic effects (dermal and epidermal changes) of long-term (24-week) daily applications of tRA and RAG on the skin, separate skin patches were measured and marked dorsally on the skin of six 21-day-old, castrated male pigs. Each skin patch area was treated daily with a cream formulation containing either 3.3 mM RAG, 16.5 mM RAG, 33 mM RAG, 3.3 mM tRA, 16.5 mM tRA or blank cream. To serve as controls, one patch received no treatment, one patch received blank cream only and for 5.3 weeks one 'washed' patch was given daily application of 33 mM RAG with routine cleansing using a mild soap typical of skin care. The amount of cream used per square centimeter remained the same during the course of the study. Biopsy tissue was collected at -1, 0, 2, 4, 8, 12 and 24 weeks from 7 test patches. The 'washed' patch was biopsied once at the 5.3-week mark. Topically applied RAG cream (3.3 mM) resulted in significantly lower histologic scores when compared with scores from tissue treated with an equimolar concentration of tRA. The highest concentration of RAG tested (33.3 mM) resulted in a response comparable to that observed in the lowest tRA (3.3 mM) treated patch area. Daily cleansing of the test area receiving 33.3 mM RAG completely eliminated any clinical signs or negative histologic changes. In conclusion, long-term topical tRA treatment in young pigs, as in humans, showed dose-dependent adverse effects on the skin, whereas RAG treatment had significantly lower histologic changes and less irritation and/or inflammation.