RESPIRATORY EPITHELIAL PERMEABILITY IN COMPLETE FREUNDS-ADJUVANT RAT LUNG GRANULOMATOSIS

To investigate Freund's adjuvant-induced changes in respiratory epithe lial permeability, we determined the respiratory epithelium clearance of Tc-99m-DTPA (RC-DTPA) in rats and the localization of horseradish p eroxidase (HRP) across the lung epithelium. RC-DTPA was determined bef ore and after intravenous injection of saline (control) or complete Fr eund's adjuvant (CFA). Although the respiratory epithelium was not dis rupted, RC-DTPA was increased 15 min after injection of CFA and was st ill high after 3 d but had returned to normal after 7 d, after which i t again increased and stayed high from Day 42 through Day 112. Cell nu mber obtained by bronchoalveolar lavage increased from 15 min to 3 d a fter injection of CFA. Lung granulomatosis was observed 14 to 112 d af ter injection of CFA; changes in RC-DTPA correlated with changes in al veolar cells. HRP was present in bronchiolar intercellular spaces only in the CFA group. We conclude that (1) RC-DTPA increases in rat lung CFA granulomatosis 15 min to 3 and 42 to 112 d following injection, (2 ) the increase in RC-DTPA is not related to a rupture of epithelium bu t (3) is proportional to the cell influx into the lung, and (4) is pos sibly caused by the opening of tight junctions in small airways.