PLASMINOGEN-ACTIVATOR INHIBITOR-1 MESSENGER-RNA IS INDUCED BY HEMORRHAGE IN ENDOTHELIAL AND MESOTHELIAL CELLS OF THE RAT-LIVER

We have recently shown that plasminogen activator inhibitor-1 (PAI-I) mRNA is elevated after hemorrhage in various tissues including liver. In this study, we set out to identify the cell types in the liver that are responsible for the increase in PAI-1 mRNA after hemorrhage using in situ reverse transcription-polymerase chain reaction (in situ RT-P CR). Male Sprague-Dawley rats were cannulated and subjected to a 20 ml /kg hemorrhage within 3 min or 300 mu g/kg of endotoxin. Four hours la ter, the livers were harvested, fixed, frozen, and sectioned. RT-PCR s howed an increase of PAI-1 mRNA in liver 4 h after hemorrhage or endot oxin-treatment. Standard in sim hybridization could not detect PAI-1 m RNA in the livers of either the hemorrhage, endotoxin, or control grou ps. However, in situ RT-PCR detected PAI-1 mRNA in vascular endothelia l cells and capsular mesothelial cells, but not in hepatocytes, in bot h the hemorrhage and endotoxin groups. No signal was found in the cont rol rats, or when the experimental protocol was modified to 1) omit th e RT step, 2) precede the RT step with RNA digestion, or 3) use an irr elevant probe. These results demonstrate that hemorrhage induces PAI-1 mRNA in endothelial and mesothelial cells of liver.