Flows of liquid and electrical current through monolayers of cultured bovine arterial endothelium.

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1. Monolayers of arterial endothelium on porous membranes were exposed to a constant pressure between 15 and 35 cmH2O. The rates of liquid flow per unit area (Jv/A) through the monolayers were monitored, together with the electrical resistance (Rm) of the endothelium. 2. At constant pressure, Jv/A decreased with an approximately exponential time course, towards a stable baseline value. This behaviour resembles the sealing previously described for cultured vascular endothelium. At 30-35 cmH2O and 37 degrees C, the mean (+/- S.E.M.) half-time (t1/2) of the decrease in Jv/A (the sealing t1/2) was 548 +/- 141 S (n = 5). The difference between the initial and baseline values of Jv/A was expressed as a fraction of the initial value. The mean (+/- S.E.M.) of this sealing fraction was 0.64 +/- 0.03 (n = 5). Mean (+/- S.E.M.) hydraulic permeability (Lp) was 23.9 +/- 6.4 x 10(-7) cm S-1 cmH2O-1 (n = 9), when measured after sealing. Endothelium appeared damaged after sealing at 30-35 cmH2O and 37 degrees C. 3. Sealing was also observed using glutaraldehyde-fixed endothelium at 30-33 cmH2O and 26-28 degrees C. There was no significant difference between the mean sealing t1/2 of these fixed monolayers, and that of unfixed endothelium at 30-35 cmH2O and 37 degrees C. However, mean sealing fraction was significantly larger for the fixed monolayers than for unfixed endothelium at 30-35 cmH2O and 37 degrees C. There were no significant difference between the post-sealing Lps of these fixed and unfixed monolayers, although the fixed monolayers appeared undamaged after sealing. 4. For unfixed endothelium, Rm was lower after sealing at 30-35 cmH2O and 37 degrees C than before pressure application. There was no significant difference between endothelial Rm before and after sealing, for glutaraldehyde-fixed monolayers. 5. Sealing was also observed at 0 degree C, using unfixed endothelium at 30 cmH2O. Mean sealing t1/2 was not significantly different from that of unfixed endothelium at 30 cmH2O and 37 degrees C. However, mean sealing fraction was significantly smaller at 0 degree C than at 37 degrees C. Unfixed endothelium appeared undamaged after sealing at 30 cmH2O and 0 degree C. Despite this, the post-sealing Lp was not significantly different from that of unfixed endothelium sealed at 30 cmH2O and 37 degrees C, after allowance was made for the effect of temperature on Lp. Rm was not measured in these experiments. 6. It is proposed that sealing is due to pressure-induced deformation of monolayers.(ABSTRACT TRUNCATED AT 400 WORDS)

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