The influence of vitamin A on the functions of the small intestine was examined in rats made vitamin A deficient for 40 days by feeding a special diet after weaning and in pair fed vitamin A deficient rats that were given supplementary vitamin A (240 IU/day) in their drinking water. The basal and stimulated electrogenic secretory and absorptive functions of the jejunum and proximal and distal ileum removed from these rats were examined in vitro using the short circuit current as the index of transport activity. The basal short circuit current in the jejunum and proximal ileum was not significantly different but that of the distal ileum was lower. Electrogenic glucose transfer was not significantly affected by the vitamin deficiency. Cholinergic stimulation using the M1/M2 agonist bethanechol showed a greatly enhanced electrogenic secretion in the jejunum of the deficient rats while secretion stimulated by dibutyryl cyclic adenosine monophosphate was significantly greater in their distal ilea compared with the supplemented group. The vitamin deficiency also disrupted the normal higher/lower hierarchical pattern of transport activity between the proximal and distal ileum. The enhanced secretory activity of the vitamin A deficient small intestine offers a putative explanation for the well known relation between vitamin A deficiency and diarrhoea found in humans.
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