British Journal of Nutrition

Vitamin A metabolism in rats

Streptozotocin-induced diabetes in rats is associated with impaired metabolic availability of vitamin A (retinol)

P. J. Tuitoeka1, S. Ziaria3, A. T. C. Tsina3, R. V. Rajottea2, Miyoung Suha1 and Tapan K. Basu*a1*

a1 Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5

a2 Surgical-Medical Research Institute, University of Alberta, Edmonton, Alberta, Canada T6G 2N8

a3 Division of Life Sciences, The University of Texas at San Antonio, San Antonio, Texas 78249-0662, USA

Abstract

Using streptozotocin-induced diabetic Wistar rats, studies were carried out to examine the metabolic availability of vitamin A in the plasma, liver and the retina of the eye. Control and diabetic rats were fed ad lib. on a semi-purified diet either with or without (basal) vitamin A supplementation, or pair-fed on the basal diet for 4 weeks. Despite the fact that diabeticrats consumed 48% more feed, they had lower plasma concentrations of retinol (P<0·003). The decrease in plasma retinol concentration was a response to diabetes (or diabetes-induced trauma), since neither pair-feeding (P<0·01) nor vitamin A supplementation altered this effect (P<0·05). Furthermore, the hepatic concentrations of the vitamin in these animals remained elevated and this increase was greater in the supplemented diabetic group (P<0·001). Decreases in 11-cis retinal (a component of rhodopsin) concentrations in the retina were also observed in diabetic animals. The increased hepatic and the decreased plasma and retina vitamin Alevels suggest a defect in the transport of the vitamin from the liver.

(Received October 05 1994)

(Revised May 22 1995)

(Accepted August 16 1995)

Footnotes

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