Gastrointestinal tract single cell

Colchicine is rapidly absorbed after oral administration and tends to concentrate in the spleen, kidney, liver, and gastrointestinal tract. Leukocytes also avidly accumulate and store colchicine even after a single intravenous injection. Since colchicine can accumulate in cells against a concentration gradient, it is postulated that an active transport process may be involved in its cellular uptake. The drug is metabolized, primarily in the liver, by deacetylation. Fecal excretion plays a major role in colchicine elimination, since it and its metabolites are readily secreted into the bile. Only about 15 to 30% of the drug is eliminated in the urine except in patients with liver disease urinary excretion is more important in these individuals. 

The arrow with an asterisk indicates the site of entry of the oral Se tracer. Arrows between compartments represent pathways of fractional transport. Compartments depicted as rectangles represent delays. Compartments G1, G2, G3, 3 gut compartments, probably the small intestine ENT, enterocytes (intestinal cells) HPL, compartment in hepato-pancreatic subsystem or lymphatic system L/P, liver and pancreas LI, large intestine T1, T2, peripheral tissues, e.g., skeletal muscle, bone, kidney. Feces and urine compartments are drawn in the shape of test tubes to represent fractional (single) collections. The model includes absorption distributed along the gastrointestinal tract, enterohepatic recirculation, four kinetically distinct plasma pools, P1-P4, a subsystem consisting of liver and pancreas, and a slowly turning-over tissue pool. 

Figure 3-12. Fraction of mitoses labeled in mucosal tissues of human subjects in the days following a single injection of tritiated thymidine. Samples were obtained by biopsy. A stomach B ileum C colon D rectum. (From Lipkin M, Sherlock P, Bell B. Cell proliferation kinetics in the gastrointestinal tract of man. V. Cell renewal in the stomach, ileum, colon and rectum. Gastroenterology 45 72 -729,1963.)...

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