Changes in the tissues of guinea-pigs fed on a diet free from vitamin A but containing methyl retinoate

Abstract

1. Forty-eight guinea-pigs were fed from weaning on a semi-synthetic diet free of retinol and carotenoids. Twenty-two of these animals received a twice-weekly supplement of methyl retinoate and fifteen received a twice-weekly supplement of retinyl acetate. The remaining eleven animals were fed on the vitamin A-free diet without supplementation.2. At varying times throughout the experiment, animals died or were killed by chloroform inhalation. Testes and seminal vesicles were weighed and these tissues together with trachea, lungs, salivary glands, bladder, eyes and vagina were examined histologically.3. The eleven guinea-pigs that received the unsupplemented diet developed signs of vitamin A deficiency after being fed on the diet for 3 or 4 weeks. Many epithelia showed a metaplastic change to the stratified squamous form often with keratinization.4. The guinea-pigs given supplements of either methyl retinoate or retinyl acetate grew at a normal rate and developed none of the signs of vitamin A deficiency that appeared in the animals on the unsupplemented diet. Evidence of metaplastic change in epithelia was not seen in any of these animals.5. Thirteen males were fed on the deficient diet and methyl retinoate. The testicles and seminal vesicles of these animals weighed less than those of the ten males fed on the deficient diet and retinyl acetate. The testes of the former showed severe histological degeneration of the seminiferous epithelium. The testes of the guinea-pigs fed on retinyl acetate were normal.6. Fifteen guinea-pigs fed on the deficient diet and retinyl acetate were mated to normal males. Eleven were thought to have become pregant. Eight of these gave birth to twenty-four pups. One died in advanced pregnancy with five apparently normal pups in utero and one produced three living young and died with one still in utero. Sixteen guinea-pigs fed on the deficient diet and methyl retinoate were mated to normal males. Twelve were thought to have conceived but all resorbed their foetuses.7. The vision of guinea-pigs fed on the synthetic diet and methyl retinoate deteriorated progressively, and after 150 days on the experiment the pupils did not respond to light. However, degeneration of the retina, such as had been seen in rats fed on a vitamin A-deficient diet containing methyl retinoate, was not seen in any of the guinea-pigs.