Liver glycerol and water permeability of obese and lean mice.

The coefficient of membrane glycerol or water permeability (Pgly and Pf, respectively) of the hepatocyte sinusoidal plasma membrane were assessed as described in Materials and Methods. (A) Glycerol permeability analysis. Representative tracings of stopped-flow light scattering of sinusoidal membrane vesicles from obese (ob/ob) and lean mouse livers in response to a 150 mM inwardly directed gradient of glycerol at 10°C. The initial increase in light scattering results from osmotic water efflux (vesicle shrinkage), followed by a slower decrease caused by glycerol entry. (B) The hepatocyte Pgly of ob/ob mice is significantly lower than lean littermates. (C) Osmotic water permeability analysis. Representative tracings of stopped-flow light scattering of sinusoidal membrane vesicles from ob/ob and control wild type mouse livers in response to a 140 mM inwardly directed hyperosmotic gradient of mannitol at 10°C. (D) The hepatocyte Pf of obese mice is moderately lower than that of lean mice. Data are mean ± S.E.M. from four independent experiments carried out using vesicles from each one of the liver preparations from six obese and six lean mice. *, P