Water and nonelectrolyte permeability of isolated rat hepatocytes.
We have measured the diffusive permeability coefficients of isolated rat hepatocytes to 3H2O, [14C]urea, [14C]erythritol, [14C]mannitol, [3H]sucrose, and [3H]inulin, employing a technique previously developed for erythrocytes (Redwood et al., J. Gen. Physiol 64:706-729, 1974). Diffusion coefficients for the tracer molecules were measured in packed hepatocytes, supernatant fluid, and intracellular medium (lysed hepatocytes) and were calculated assuming one-dimensional semi-infinite diffusion through a homogeneous medium. By applying the series-parallel pathway model, the following permeability coefficients (10(-5) cm/sec) for the hepatocyte plasma membrane were obtained. 3H2O, 98.6 +/- 18.4; [14C]urea, 18.2 +/- 5.3; [14C]erythritol, 4.8 +/- 1.6; [14C]mannitol, 3.1 +/- 1.4; [3H]sucrose, 0; [3H]inulin, 0. These results indicate that isolated rat hepatocytes are highly permeable to water and polar nonelectrolytes, when compared with other transporting epithelia. This relatively high cellular permeability is consistent with a model in which nonelectrolyte permeation is via an aqueous pathway of equivalent pore diameter of 8-12 A. The finding that [14C]erythritol and [14C]mannitol cross the hepatocyte plasma membrane indicates that these molecules enter the bile canaliculus through the transcellular route. Conversely, the failure of [3H]sucrose and [3H]inulin to permeate the hepatocyte in the isolated condition supports the concept that biliary entry of these large carbohydrates, at least that fraction which cannot be accounted for by a vesicular mechanism, must occur via the transjunctional shunt pathway.
D000818:Animals; D001834:Body Water / Q000378:metabolism; D002250:Carbon Radioisotopes; D002463:Cell Membrane Permeability; D003911:Dextrans / Q000378:metabolism; D004896:Erythritol / Q000378:metabolism; D066298:In Vitro Techniques; D007444:Inulin / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008353:Mannitol / Q000378:metabolism; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains; D013395:Sucrose / Q000378:metabolism; D014316:Tritium; D014508:Urea / Q000378:metabolism
D002250:Carbon Radioisotopes; D003911:Dextrans; D014316:Tritium; D008353:Mannitol; D013395:Sucrose; D014508:Urea; D007444:Inulin; D004896:Erythritol