Correlations among pH and Mg, Ca, P, Na, K, Cl^- and HCO^-₃ Contents of Digesta in the Gastro-Intestinal Tract of Rats

Abstract

pH and Mg, Ca, P, Na, K, Cl^- and HCO^-₃ contents of digesta in the stomach, the small intestine, the caecum, the colon were determined in the rats to study the effects of pH on absorption of Mg, Ca and P in the gastro-intestinal tract. Acidification in the stomach (pH3.46), sudden pH rise in the upper segment of the small intestine (pH6.52), sudden alkalization from pH6.89 to pH7.41 in the defined site of the lower segment of the small intestine, acidification in the caecum (pH6.91) and sudden alkalization in the colon (pH7.97) were observed. The positive correlations among Cl^-, HCO^-₃, Na and K contents suggested that these minerals neutralized the low pH by HCl secreted in the stomach and organic acids produced by fermentation in the caecum. The significant negative correlations between pH and the ratio of Mg, Ca or P contents (Sup %) in supernatant fraction to total contents showed the possibility that the insoluble salts of these minerals precipitated as pH rose. The sudden increase of P content in the caecum might be due to the accumulation of P into multiplied bacteria. These results suggested that the sudden alkalization of digesta might decrease the absorptions of Mg, Ca and P in the intestine.