Isoflurane- and halothane-mediated dilation of distal bronchi in the rat depends on the epithelium.
BACKGROUND
Respiratory epithelium releases substance(s) that can modulate bronchoconstriction in response to constrictive agonists and enhance bronchodilation in response to certain bronchodilators. The hypothesis that the bronchodilatory effect of isoflurane and halothane depends on the epithelium was tested in rat distal bronchial segments.


METHODS
Wistar rat bronchial segments of the fourth order (diameter approximately 100 microns) were dissected. After preconstriction with 5-hydroxytryptamine, each bronchial segment was exposed to increasing concentrations of 0% to 3% isoflurane or 0% to 3% halothane under four conditions: after epithelial rubbing, after pretreatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine, after pretreatment with the cyclooxygenase inhibitor indomethacin, or with no preintervention (control). Changes in bronchial diameter were monitored using an in vitro video detection system.


RESULTS
Both isoflurane and halothane produced concentration-dependent bronchodilation (P < 0.001 for either anesthetic; 40% +/- 11% [mean +/- SD] dilation for 3% isoflurane and 57% +/- 10% dilation for 3% halothane). For both anesthetics, bronchodilation was significantly but incompletely attenuated by epithelial rubbing (12% +/- 7% dilation for 3% isoflurane [P < 0.01] and 31% +/- 10% dilation for 3% halothane [P < 0.01]), by pretreatment with indomethacin (20% +/- 8% dilation for 3% isoflurane [P < 0.02] and 21% +/- 9% dilation for 3% halothane [P < 0.001]), or by L-NNA (9% +/- 7% dilation for 3% isoflurane [P < 0.005] and 39% +/- 12% dilation for 3% halothane [P < 0.05]). Epithelial rubbing did not impair nitroprusside-associated bronchodilation.


CONCLUSIONS
Isoflurane- and halothane-mediated bronchodilation depends at least partially on the epithelium and may involve both a prostanoid and nitric oxide in distal rat bronchi.
Park
K W
KW
Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA. kyungwonpark@mcm.po.com
Dai
H B
HB
Lowenstein
E
E
Kocher
O N
ON
Sellke
F W
FW
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001980:Bronchi / Q000187:drug effects* / Q000502:physiology; D016084:Bronchoconstriction / Q000187:drug effects; D001993:Bronchodilator Agents / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005260:Female; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology
D018685:Anesthetics, Inhalation; D001993:Bronchodilator Agents; D012701:Serotonin; D007530:Isoflurane; D006221:Halothane