Endothelial cell permeability to water and antipyrine

The endothelium provides a structural barrier between plasma constituents and the tissues. The permeability characteristics of the the endothelial cells regulate the transcellular movement of materials across this barrier while other movement is paracellular. In this study the permeability of the endothelial cells to tritiated water (3HHO) and 14C-labeled antipyrine (AP) was investigated. The cells were isolated non-enzymatically from calf pulmonary artery and were maintained in culture and used between the seventh and fifteenth passage. The cells were removed from the T-flasks with a rubber policeman, titurated with a 22g needle and centrifuged. The cells were mixed with an extracellular marker, drawn into polyethylene tubing and packed by centrifugation for use in the linear diffusion technique. All measurements were made at 37 C. The diffusion coefficients for 3HHO through the packed cells (D), the intracellular material (D2), and the extracellular material (D1) were 0.682, 0.932 and 2.45 x 10-5 cm2 s-1 and for AP were 0.273, 0.355 and 1.13 x 10-5 cm2 s-1 respectively. The permeability coefficient calculated by the series-parallel pathway model for 3HHO was higher than that for AP and for both 3HHO and AP were lower than those calculated for isolated lung cells and erythrocytes