The Role of Nitric Oxide in Airway Responsiveness in Diabetic-Antigen Sensitized Guinea Pigs in Vitro

Clinical asthma and airway responsiveness appear to be less severe when diabetes is superimposed. The aim of the present study was to determine the possible role of Nitric Oxide (NO) in the airway reactivity under diabetic and diabetic-allergic conditions. Twenty-five male guinea-pigs were divided into five groups of five each as follows: diabetic, antigen sensitized, diabetic- antigen sensitized, insulin-treated diabetic- antigen ovalbumin sensitized and control animals. Tracheal rings of all groups were mounted in an organ bath system for isometric contraction measurements. Tissues were pre-incubated with either of the following chemicals: L-NAME, L-arginine or methylene blue. Cumulative concentration response curve was made with histamine. Decrease in the airway reactivity in diabetic and diabetic- antigen sensitized animals were shown compared to the antigen sensitized animals. pEC50 values of histamine in the presence of L-Arg showed increase in diabetic and diabetic- antigen sensitized animals compared to the controls. In the presence of methylene blue, these values showed an increase in diabetic and diabetic- antigen sensitized animals compared to the controls. However, incubation with L-NAME did not change the airway responsiveness to histamine in diabetic and diabeticantigen sensitized animals compared to the controls. Experimental diabetes causes were found to decrease the responsiveness of tracheal rings in the presence or absence of allergy. Findings of this research work showed that NO had no role in hypo-responsiveness of airway in diabetic and diabetic- antigen sensitized animals.