Influence of supplemental dietary vitamin A on the reproductive performance of iodine-toxic rats.
Several indications of metabolic interactions between vitamin A and iodine prompted this experiment to determine if oral vitamin A supplementation would alleviate the effects of iodine toxicity using aspects of reproductive performance of rats as criteria. Sprague-Dawley female rats were acclimated to a purified diet and assigned, at breeding time, to 2 X 3 factorial experiments (n = 60) to test the effects of 600 and 12,000 IU vitamin A (experiment 1) and 12,000 and 480,000 IU vitamin A (experiment 2) as retinyl palmitate per kilogram diet, on the reproductive performance of rats fed 0.2, 500 and 1,000 ppm iodine. At these dietary levels of iodine, the daily iodine intake of the rats during gestatin in both experiments was 0.003, 8.8 and 17 mg, respectively, and was not affected by vitamin A intake. The iodine intakes correlated positively with the percentage of stillborn pups per litter, negatively with packed cell volumes of the whelping dams and negatively with the survival rates of their liveborn pups. Most pup deaths occurred within 24 hours postpartum and were attributed to the iodine-induced anemia and/or agalactia. Vitamin A supplementation did not significantly reduce the effects of iodine toxicity on the parameters measured, although there was a tendency for vitamin A to reduce the percent of stillbirths in litters of dams fed 1,000 ppm iodine, to increase the number of weaned pups per litter of dams fed 500 or 1,000 ppm iodine and to maintain relative liver size of the iodine-toxic dams during lactation.