Evaluation of airway smooth muscle contractions in vitro by high-frequency ultrasonic imaging.
To visualize ASM contraction in vitro, we measured changes in cross-sectional area and inner circumference of isolated porcine and human bronchi in response to acetylcholine or carbamylcholine chloride (Carbachol) using high-frequency ultrasound. A mechanical ultrasonic catheter (20 MHz; diameter, 1.7 mm; echo element, 1 mm2) demonstrated three histologic layers (mucosa, cartilage and adventitia) and allowed measurement of dose-dependent contraction of porcine bronchi over time. Acetylcholine (10(-4)M) significantly decreased the cross-sectional area by 17 +/- 2.85 percent but did not change the circumference. The mean initial value for area was 0.6 +/- 0.08 cm2 and for circumference was 3.0 +/- 0.24 cm (n = 5). The EC50 of acetylcholine was 1.5 x 10(-8) M. Carbachol (10(-4)M)-induced contractions of human bronchi were also observed under the same conditions. In conclusion, high-frequency ultrasonic imaging can be used to study the morphology of ASM contractions in vitro, providing valuable information on the natural dynamics of ASM.
Iizuka
K
K
First Department of Internal Medicine, Gunma University School of Medicine, Japan.
Dobashi
K
K
Houjou
S
S
Sakai
H
H
Itoh
K
K
Nakazawa
T
T
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000166:cytology / Q000000981:diagnostic imaging* / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D013552:Swine; D014463:Ultrasonography
D002217:Carbachol; D000109:Acetylcholine