ABSTRACT
In 10 southern Indian patients with tropical sprue, in vivo dialysis showed a defect of absorption of water and sodium from the rectum, when compared with 11 healthy volunteers. Sodium-potassium-ATPase activity, measured in homogenates of rectal biopsies, was significantly diminished in patients with sprue. Magnesium-ATPase and alkaline phosphatase were normal in biopsy homogenates. Decreased activity of colonic sodium-potassium-ATPase may contribute to diarrhoea in some patients with tropical sprue.
Subject(s)
Rectum/metabolism , Sodium-Potassium-Exchanging ATPase/metabolism , Sodium/metabolism , Sprue, Tropical/metabolism , Water/metabolism , Humans , Intestinal Absorption , Intestinal Mucosa/metabolism , Rectum/enzymology , Sprue, Tropical/enzymologyABSTRACT
Faecal excretion of fatty acids is increased in patients with tropical sprue because of unabsorbed dietary fatty acids. The excretion of fatty acids correlates well with faecal wet weight. In vitro unsaturated fatty acids inhibited Na K-ATPase and Mg-ATPase isolated from basolateral membranes of enterocytes and colonocytes. These findings are a possible explanation for the observed abnormalities in water and electrolyte absorption by the colon in patients with tropical sprue and steatorrhoea.
Subject(s)
Adenosine Triphosphatases/antagonists & inhibitors , Diarrhea/etiology , Fatty Acids, Nonesterified/analysis , Sprue, Tropical/metabolism , Animals , Colon/enzymology , Dietary Fats , Fatty Acids, Nonesterified/pharmacology , Feces/analysis , Humans , Intestine, Small/enzymology , Rats , Sprue, Tropical/enzymologyABSTRACT
Despite the high prevalence of intestinal lactase deficiency in some racial groups and in patients with intestinal disease, the biochemical defect has not been characterized. In the preceding paper normal intestine was found to have two lactases with distinctly different pH optima. Therefore, pH activity curves of homogenates from lactase-deficient intestine were studied, and the pH optimum was found to be shifted from the normal of 5.8 to 4.8. Density gradient ultracentrifugation of intestinal material from five lactase-deficient patients demonstrated absence of a lactase with pH optimum 6.0 and molecular weight 280,000. A second lactase with pH optimum 4.5 and molecular weights of 156,000 and 660,000 remained at normal levels accounting for the shift in the pH optimum in whole intestinal homogenates. In addition, three of the five patients had absence of a smaller beta-galactosidase (molecular weight 80,000) that had specificity only for synthetic substrates. Although not a lactase, this enzyme had a pH optimum identical with the missing lactase, and its activity was inhibited by lactose in a partially competitive manner suggesting that it is capable of binding lactose. It is possible that this enzyme is a precursor or fragment of the missing lactase.The residual lactase activity provided by the lactase with low pH optimum represents 20-70% of the activity of the missing enzyme, and yet these patients are not able to digest dietary lactose. Thus it appears that the residual enzyme plays no significant role in the hydrolysis of ingested lactose.
