ASSESSMENT OF AGONIST-MEDIATED AND CELL-MEDIATED RESPONSES IN AIRWAY MICROSECTIONS BY COMPUTERIZED VIDEOMICROMETRY

The objective of this investigation was to develop a method for real-t ime measurement of changes in luminal area in microexplants of airways during pharmacological and physiological interventions. After guinea pig; were killed, tracheal rings (1- to 2-mm thick) were excised and p laced in 300-mu l chambers. The area of the airway lumen was calculate d as pixel number with the use of computerized videomicrometry. In 29 epithelium-intact airways, 10(-3) M acetylcholine (ACh) caused decreas e in luminal area of 38.1 +/- 2.80% (P < 0.001 vs. 10(-9) M). Spontane ous tone also was demonstrated in 34 preparations from 4 guinea pigs; decrease in area of 17.0 +/- 1.45% after 60-min incubation in buffer a lone was blocked completely by 10(-5) M indomethacin (P = 0.01). Lumin al narrowing caused by less than or equal to 10(-6) M Ach was reversed completely by 10(-6) M albuterol (P = 0.002). Addition of 100,000 act ivated human eosinophils caused 24.7 +/- 4.41% decrease in luminal are a vs. 7.24 +/- 5.51% for nonactivated cells (P = 0.048). We demonstrat e a real-time method for the assessment of auxotonic changes in airway caliber that utilizes microsections of explanted airways and permits the use of extremely small numbers of isolated cells to achieve physio logical activation. Concentration-response characteristics and spontan eous tone are similar to those of large chamber preparations, and narr owing is reversed by beta(2)-adrenoceptor activation.