1. Young rats were kept for several weeks on a diet deficient in vitamin A. Some were undosed, others were given marginal (25i.u. weekly), adequate (1000i.u. weekly) or excessive (50000i.u. daily) doses of vitamin A acetate. The undosed rats developed signs of vitamin A deficiency, and the overdosed animals had skeletal fractures indicative of hypervitaminosis A. 2. The rats were decapitated. T...

Young male Sprague-Dawley rats were fed oral supplements of vitamin A; either a subtoxic dose of 5000 i.u./day for 16 weeks (10 animals), or a toxic dose of 15,OOOi.u./day for 16 days (5 animals). High-dose animals exhibited signs of acute toxicity; low-dose animals demonstrated only less weight gain than controls. Vitamin A sera and liver levels evidenced intoxication. Light and electron micro...

Toxic effects of administering large doses of vitamin A have been known for a long time to occur in human beings as well as in laboratory animals (Josephs, 1944; Knudson & Rothman, 1953). Polar bear liver is an unusually potent source of vitamin A and is toxic as a food even for Eskimo's dogs (Rodahl & Moore, 1943). I n hypervitaminosis A basal metabolism is lowered (Sadhu & Brody, 1947) and li...

Vitamin A status was examined in nine adult cystic fibrosis patients and six adult control subjects, together with an assessment of their ability to absorb 10,000 IU of retinyl palmitate from a test meal, taken with appropriate pancreatic enzyme supplements. Median baseline values for plasma retinol and carotene, as well as median serum retinol binding protein concentrations, were significantly...

The effect of vitamin A deficiency and hypervitaminosis A on the urothelial carcinogenicity of N-[4-(5-nitro-2-furyl)-2-thiazolyl]formanmide (FANFT) was determined in female weanling Sprague-Dawley rats. Vitamin A deficiency resulted in squamous metaplasia of the urinary bladder and high incidences of cystitis, ureteritis, and pyelonephritis. Administration of FANFT to vitamin A-deficient rats ...

Studies of hypervitaminosis A in animals and anecdotal reports of accidental vitamin A poisoning in humans suggest impairment of bone remodeling and increased numbers of fractures. Because of the widespread use of high-dose vitamin A supplements which may produce subclinical hypervitaminosis associated with decreased bone mass and increased risk of fracture, we studied the relationship between ...