Steroid effects of the lung a Leukotriene promotes contraction of smooth muscle of the bronchioles n Histamine increases vascular permeability, causing capillary eakage and edema Why asthma makes it hard to breathe ed bronchial tube Normal bronchial tubeSteroid effects of the lung  Leukotriene promotes contraction of smooth muscle of the bronchioles  Histamine increases vascular permeability, causing capillary leakage and edema