Effect of lactate and H+ on structure and function of rat intestine

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Abstract
Segments of rat ileum and colon were infusedin vivo to test if 0.1 M lactate, 10−4 M H+ or both altered mucosal structure and function. In the first series of experiments, lactate concentration was kept at 0.1 M while H+ was varied from 10−4 to 10−7 M. Lactate and 10−4 M H+ in the colon, and lactate and 10−5 M H+ in the ileum depressed net water transport and caused sloughing of superficial absorptive cells. In the second series of experiments, H+ concentration was kept at 10−4 by using carboxymethylcellulose, rather than organic acids, to buffer the infusion mixture; the concentration of lactate was varied from 0 to 0.1 M. Mucosa remained normal after infusions of 10−4 M H+ alone. Addition to the 10−4 M H+ infusion of 0.1 M, lactate in the colon or 0.075 M lactate in the ileum caused increased mucosal sloughing. Thus lactate plus H+ (or unionized lactic acid) alters colonic and ileal mucosa. Because such high concentrations of lactate and H+ are found in subjects malabsorbing carbohydrates, the present experiments support the contention that H+ and organic acids are etiological factors in some cases of chronic fermentative diarrhea.