ABSTRACT
Rats were divided into 6 groups fed with 2 levels of zinc (1.41 and 100 ppm) and 3 levels of vitamin A (retinyl acetate 0, 7 and 46 mg/kg). Each group of the rats was tube-fed for 18 days and killed on the 19th day of experiment. Growth rate, zinc and vitamin A levels in serum and tissues, alkaline phosphatase (AKP) activity in serum, total protein and hemoglobin concentrations were measured. Both zinc levels in serum and tissues and AKP activity of the zinc deficient groups were significantly lower than those of the control group. The serum vitamin A values were distinctively depressed in the vitamin A free and vitamin A normal group. The serum vitamin A values in the vitamin A enriched group were not affected by zinc deficient diet and its serum zinc levels was higher than vitamin A free and normal group. The results suggest that zinc deficiency will interfere the release of vitamin A from liver and lead to the decrease of blood vitamin A, which may occurs only when the blood zinc is lower than a certain "critical level" . Different levels of vitamin A have different effect on rats of zinc deficiency, such as vitamin A deficiency will aggravate the zinc deficient symptoms and the increase of vitamin A intake can alleviate zinc deficient harms.