LUNG EPITHELIAL PERMEABILITY AND BRONCHIAL RESPONSIVENESS IN SUBJECTSWITH STABLE ASTHMA

Lung epithelial permeability of asthmatic patients has been reported t o be similar or lower than that of healthy subjects and to be correlat ed or not to bronchial hyperresponsiveness. To clarify these discrepan cies, we evaluated Tc-99m-DTPA pulmonary clearance in a group of caref ully selected asthmatic patients with mild, stable asthma (n=13; seven women; mean age+/-SD=27.69+/-6.63 years), and compared them with a gr oup of healthy, nonsmoking subjects (n=8; six women; mean age+/-SD=24. 38+/-5.15 years). Selection criteria for asthmatics were as follows: b aseline FEV1 greater than or equal to 80% of predicted values, no bron chial infections, and/or no asthma attacks during 4 weeks prior to stu dy and peak expiratory flow rate variability lower than 20%, over a pe riod of 3 weeks. Patients controlled symptoms with beta(2)-adrenergic drugs only, regularly or on demand. Mean baseline FEV1 (+/-SD) as perc ent of predicted was 102.38+/-13.97 and 112.88+/-18.36, respectively ( p <0.05). In the asthmatic group, bronchial responsiveness to methacho line (PC20 M FEV1) ranged between 0.55 and 28.5 mg/mL. Mean value (+/- SD) of DTPA clearance from lungs to blood (evaluated on the first 10 m in out of 30 min of the curves) in the asthmatic group was not differe nt from that of control group (68.31+/-21.46 and 69.5+/-15.73). In the asthmatic patients, there was no correlation between PC20 M values an d DTPA T1/2 min of the whole lung, nor between PC20 M and inner and ou ter lung clearance zones, Moreover, both in asthmatics and healthy sub jects, DTPA clearance of outer (alveolar) zones was significantly fast er than that of inner (bronchial) zones (57.69+/-19.94 vs 102.08+/-38. 19, p <0.001, and 59.75+/-12.49 vs 103.5+/-31.86, p <0.003, respective ly). Our data show that DTPA clearance in patients with stable asthma is similar to that found in healthy subjects; it is not. correlated to degree of bronchial responsiveness and occurs more rapidly in the out er zones than in the inner zones, both in asthmatic patients and in he althy subjects, Thus, to date, DTPA clearance index is not a valid too l for identifying and/or monitoring asthmatic patients.