Effect of Force-feeding a Valine-free Diet on Gastrointestinal Function of Rats

Abstract

To study the effect of an essential amino acid deficiency on gastrointestinal functions, rats were force-fed a 10% amino acid diet devoid of valine for several days, and subsequently a complete amino acid diet. Force-feeding of the valine-free diet for a few days delayed the disappearance of dietary nitrogen from the gastrointestinal tract. ASINGLE FEEDING OF THE COMPLETE AMINO ACID DIET CONTAINING 14C-labeled amino acids or (14C)glucose to rats previously fed the valine-free diet did not improve disappearance of the nitrogen. The absorption of the dietary carbohydrate as well as dietary nitrogen was delayed after feeding the valine-free diet. In spite of the delayed disappearance of dietary 14C-labeled amino acids or (14C)glucose from the gastrointestinal tract, the incorporation of these dietary 14C-labeled amino acids into liver lipids was not different between rats fed the complete amino acid diet and those fed the valine-free diet. Under these experimental conditions, changes in disaccharidase activities in the intestinal mucosa were in parallel with changes in the disappearance of nutrients from the gastrointestinal tract.

Effect of diets supplemented with amino acids on intestinal sucrase and leucine aminopeptidase activities in rats.

“…SOLIMANO et al (4) and ADAMS and LEICHTER (7) proposed that this lack of agreement between human and animal responses to protein deficiency might be due to a number of factors, to deficiency in protein as well as other nutrients and gastrointestinal infection. Recently, however, we found that in rats under force feeding or ad libitum feeding conditions the activities of intestinal disaccharidase and leucine aminopeptidase (LAPase) per length of the small intestine , that is, the segmental activities, were affected by the composition of dietary amino acids and protein (8)(9)(10)(11). The segmental activities of these enzymes were considered to be more substantial measures of the total functional capacities than the enzyme activities per mg of mucosal protein, that is, the specific activities, because these enzyme activities were localized in the brush border membrane of the small intestine (12,13), and the length of the small intestine was little altered by different dietary conditions , whereas in several instances there was substantial reduction in its weight (14,15).…”

Nutritional significance of intestinal sucrase activity in rats.

“…A certain amount of evidence suggesting that the intestinal sucrase activity in rats plays an important role in the digestion and absorption of dietary sucrose has been obtained from many investigations (1)(2)(3)(4)(5)(6). Little, however, indicates the physiological role of this enzyme activity in the nutritional condition at the level of the whole body.…”

Effects of Fish Meal as Source of Protein on Intestinal Maltase Activity and Intestinal and Renal Leucine Aminopeptidase Activity of Growing Rats

“…The intestinal maltase and LAPase activities were affected not only by dietary carbohydrate [ 14] but also by the amino acid composition and protein content of the diet [7,15,16].…”