PASSIVE SENSITIZATION OF HUMAN BRONCHI AUGMENTS SMOOTH-MUSCLE SHORTENING VELOCITY AND CAPACITY

We assessed whether incubation with human serum from atopic individual s containing high concentrations of immunoglobulin E (IgE) causes augm entation of maximal contraction of human bronchial smooth muscle from nonatopic subjects in vitro. Bronchi were obtained from eight patients undergoing lung resection, and force-velocity relationships were dete rmined for eight pairs of epithelium-intact bronchial rings of generat ions 6-7 using an electromagnetic lever system, which allowed isotonic shortening when load-clamps [from 0 to maximal isometric force (P-o)] were applied at specific times after onset of contraction. Contractio ns were elicited by supramaximal electrical field stimulation (50 Hz, 10 strain duration, 25 V). Optimal length (L(o)) for each tissue was d etermined during equilibration. After resection, tissues were sensitiz ed passively with human sera containing high titers (> 1,000 U/ml) of IgE by incubation for 16 h at 20 degrees C. Maximal shortening velocit y (V-max) was increased for passively sensitized bronchi [0.1150 +/- 0 .0240 1/2 circumferences/s (1/2Cir/s)] compared with sham-sensitized b ronchi [0.0731 +/- 0.0152 1/2Cir/s, P = 0.038]. Similarly, maximal sho rtening (Delta L(max)) was augmented in sensitized bronchial rings (11 .27 +/- 1.80 %L(o)) compared with sham-sensitized tissues (8.19 +/- 1. 39 %L(o), P = 0.012). However, P-o did not differ between sensitized ( 122.5 +/- 24.4 mN/cm(2)) compared with sham-sensitized tissues (138.4 +/- 32.1 mN/cm(2), P = 0.642). Our data are the first demonstration th at V-max and Delta L(max) are augmented in sensitized but not challeng ed human bronchial rings after passive sensitization using human serum containing high concentrations of IgE.