Representative histological features of lung vascular smooth muscles in a guinea pig allergic asthma model. A) Low-power micrograph (10x) from the lungs of control and asthma model guinea pigs showing a bronchus and an arteriole. Note the extensive smooth muscle (SM) area in the asthma model arteriole. B) Area of arteriole SM layer, as measured by automated morphometry (n = 6 per group). C) Systemic arterial pressure and D) pulmonary arterial pressures (n = 4 and 8 guinea pigs in control and asthma model group, respectively). Bars and vertical lines are mean ± SE. *P < 0.01 (unpaired Student’s t-test).