Experimental intestinal malabsorption states and their relation to clinical syndromes

Change in small intestinal brush border membranes of rats following methotrexate administration

Change in small intestinal brush border membranes of rats following methotrexate administration was monitored by the fluorescence spectra and polarization of the cationic fluorescent probe, safranin 0. Total protein content of brush border membranes of treated rats was less than that of control rats, whereas no significant difference in total sialic acid content of brush border membranes was observed between them. Thus, an apparent increase in the electronegative charge of brush border membrane vesicles per unit of membrane protein following methotrexate administration may possibly cause the change in fluorescence spectra and polarization of safranin 0.

Diarrhoea and constipation

Drug-induced constipation is mostly caused by changes in gut motility, whilst diarrhoea is more frequently caused by an increase in intestinal fluid secretion. In both instances the drug has to reach the enteric nervous system or the enterocyte, either via the blood or from the lumen, in sufficient concentrations to affect the mediators that regulate motility and fluid transport. Diarrhoea and constipation are frequently mentioned as side-effects of drugs, and therapeutic agents for almost all organ systems have been implicated. However, both these side-effects are usually mild or moderate, and rarely necessitate interruption of drug treatment. An exception to this rule is the antibiotic-associated colitis seen in patients treated with antibiotics such as lincomycin or clindamycin; in principle almost all antibiotics may cause this severe and potentially life-threatening complication. Other rare forms of severe, drug-induced colitis and diarrhoea result from toxic or anaphylactic reactions against gold preparations, cytostatic agents and sulphonamides. Ischaemic colitis due to vascular complications has been described in some women taking oral contraceptives, and in patients treated with vasopressin or digitalis.

Alterations in the dog renal tubular epithelium during normothermic ischemia

Dog kidneys were subjected to one, two, or three hours' normothermic ischemia in situ and were then excised for biochemical and histological evaluation. The uptake of para-aminohippurate (PAH) by cortical slices progressively decreased with prolongation of the ischemia, but active transport was never abolished. Glycine uptake and oxygen consumption were only reduced to a modest extent by the ischemia. The intracellular ion levels were drastically altered, with loss of potassium and gain of sodium and chloride, and considerable increases in tissue water were observed. Acid phosphatase was liberated by the whole organ into the venous blood and by the incubated slices into the incubation medium, but both biochemical and histochemical techniques showed that the total quantity of the enzyme in the cells was hardly changed. The histochemical reaction product was localized exclusively in the lysosomes. Morphological damage was slight after one or two hours' ischemia, but more pronounced after three hours, when some cells were seen to be detached from the basement membrane. These relatively minor changes seem insufficient to predict the ultimate fate of the organ after ischemia.

Disaccharidases in rat small intestinal mucosa following cytostatic treatment with adriamycin

Our studies have shown that appropriate doses of adriamycin can reduce the activities of the intestinal disaccharidases in the rat. At higher doses, in addition to morphological changes in the intestinal mucosa, a considerable fall in disaccharidase activities also occurs. This functional impairment can be seen for a period of several days after the morphological restitution of the mucosa. Appropriate studies of the small intestinal mucosa in man will have to be undertaken to show whether similar impairment occurs at therapeutic doses.

The recovery of function and microcirculation in small intestinal loops following ischaemia

Short loops of dog small intestine, filled with a buffered glucose solution, were subjected to one hour's total ischaemia by clamping the corresponding mesenteric artery and vein as well as the intestinal wall at each end of the loop. Immediately after the ischaemic period and 24 hours later, their functional capacity, together with that of neighbouring control loops, was determined by studying the absorption of phenylalanine and beta-methyl-glucoside in vitro and by measuring the levels of Na(+)-K(+)-ATPase in the mucosa. The release of lysosomal enzymes after the ischaemia was studied by gauging the levels of acid phosphatase in the venous blood draining the ischaemic loop. The state of the mucosal microcirculation was investigated by injection of indian ink into the mesenteric artery removal of the loop. Immediately after ischaemia, considerable structural damage was observed in the intestinal mucosa, with desquamation of the villous tips, oedema, vascular stasis, and haemorrhagic infiltration in the lamina propria. No dye was observed in the mucosal capillaries. All transport capacity was abolished, but ATPase levels were unchanged. A significant release of lysosomal enzymes into the venous blood was noted. One day later structural and functional recovery was complete, and vascularization of the villous core was restored.