Restricted transport of cationic macromolecules across intestinal capillaries.
The charge-selective properties of intestinal capillaries were investigated by measuring steady-state lymph-to-plasma concentration ratios (L/P) of endogenous and exogenous macromolecules of comparable molecular size but different charge. The steady-state L/P values for endogenous lactate dehydrogenase isoenzymes (LD1-LD5) decreased with increasing isoelectric point. The osmotic reflection coefficient for LD1, the most negative isoenzyme studied, was 0.71 +/- 0.01; that for the most positive isoenzyme (LD5) was 0.95 +/- 0.01. The steady-state L/P for an exogenous molecule, neutral dextran, was 0.51 +/- 0.04; the L/P for the positively charged dextran of similar size was 0.25 +/- 0.04. The results indicate that intestinal capillaries behave as a positively charged barrier that reduces blood-lymph exchange of cationic macromolecules and enhances the exchange of anionic molecules.
D000818:Animals; D001692:Biological Transport; D002196:Capillaries / Q000378:metabolism*; D002412:Cations; D002415:Cats; D003911:Dextrans / Q000378:metabolism; D006801:Humans; D007420:Intestine, Large / Q000098:blood supply*; D007421:Intestine, Small / Q000098:blood supply*; D007527:Isoenzymes; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008196:Lymph / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism
D002412:Cations; D003911:Dextrans; D007527:Isoenzymes; D012709:Serum Albumin; D007770:L-Lactate Dehydrogenase