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Influence of some physiologic and dietary factors on plasma sterol concentration in bile acid excretion in the domestic chicken Lindsay, Owen Burnett

Abstract

An in vivo technique was developed for the purpose of determining the rate of absorption of bile salts by the mesenteric small intestine of the chicken. Using this technique, it was found that the absorptive capacity of the intestine for sodium taurocholate and sodium glycocholate increases distally. The possibility was investigated that the amount of bile salt reabsorbed from the intestine determines the level of circulating sterols in the chicken. Intestinal absorption of sodium taurocholate was accordingly determined in birds selected to show a wide range in levels of circulating sterols. Absorption of the bile salt was tested with concentrations of taurocholate equivalent to 0.15 and 0.75% cholic acid, using open segments of intestine. Data obtained from 20 birds showed that the level of circulating sterols and the rate of bile salt absorption were not significantly correlated. The lack of a significant correlation was considered to be probably due in part to variation in the effect of diet on the availability of bile salts for reabsorption. The rate of bile acid excretion and the concentration of circulating sterols were therefore determined in birds fed diets supplemented with triglycerides, of varying degree of unsaturation, soyalecithin and beta sitosterol. It was found that a diet supplemented with 15% coconut oil induced an elevation in the level of plasma sterols when substituted for a low-fat diet but that diets supplemented with corn oil and herring oil, induced little or no change in this level. The change to a fat-enriched diet was associated with a decrease in the fecal output of bile acids. The decrease was greater when coconut oil rather than corn oil or herring oil was fed, indicating that the plasma sterol lowering property of unsaturated fats is due at least in part to their enhancing effect on bile acid excretion. Diets to which 2.5% soyalecithin and 0.5% beta sitosterol were added, effected a slight reduction in the level of plasma sterols. The addition of soyalecithin to the diet resulted in a significant increase (P < 0.01) in the growth rate of the birds studied. The amount of bile acids excreted was increased significantly (P < 0.01) by the addition of soyalecithin to the diet. The addition of beta sitosterol to the diet resulted also in an increase in bile acid excretion. The increase approached significance at the 5% level of significance (F ratio calculated = 7.53, significant F ratio = 7.71). The increase in bile acid excretion resulting from the administration of the soyalecithin supplemented diet was considered to be the net result of two opposing effects. One effect was an increase in the reabsorption of bile acids. It was evidenced by a further increase in the plasma sterol level of the lithocholic acid-fed chick in response to dietary soyalecithin. The other effect was reasoned to be an increase in the biliary excretion of bile acids and/or bacterial alteration of bile acids in the digestive tract.

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