Dzialoszynski, Mystkowski & Stewart (1945) showed that vitamin A was present in human blood as a protein complex and not in the colloidal state. This idea was further extended by Ganguly, Krinsky, Mehl & Deuel (1952) and by Ganguly & Krinsky (1953), who suggested that a specific carrier protein probably maintained a steady vitamin A alcohol concentration in the blood. Also, Krinsky, Cornwell & Oncley (1958) have shown that vitamin A alcohol and vitamin A ester are transported by two separate lipoproteins in human blood. Some recent observations have, however, focused attention on the coincidence of widespread protein malnutrition and vitamin A deficiency in human beings in many parts of the world, and have led to
1. Young rats with low reserves of vitamin A were dosed with retinal in groundnut oil, and the stomach, the contents, mucosa and muscles of small intestine, the blood and the liver were analysed at periods up to 24hr. after dosing. 2. Up to 6hr. after the dose, retinal was present in high concentrations in the contents, mucosa and muscles of the intestine. Small but significant amounts were present in blood and liver at all times. 3. The intestinal mucosa and muscles always contained small amounts of retinol and its esters. 4. A study of the distribution of the three forms of the vitamin within the mucosal cell showed that most of the mucosal retinal enters the cell unchanged. 5. When protein-depleted rats were similarly given retinal, the rate of reduction of the aldehyde, and the consequent deposition in the liver of retinol and its esters, progressively decreased with reduced protein intake.
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