Figure 2: Changes in the contractile responses of the mesenteric artery following intratracheal instillation (IT) of MWCNTs The changes in the contractile responses were assessed by wire myography of the first order mesenteric artery from 17 - 19 days pregnant (A, C, E and G) and nonpregnant female (B, D, F and H) Sprague Dawley rats, 24 hours following intratracheal instillation (IT) of 100 μg/kg of (S)-MWCNTs or 10% surfactant. The stress generation in response to cumulative concentrations of phenylephrine (PE; A and B), endothelin 1 (ET-1; C and D) and serotonin (5HT; E and F) are plotted. The percentage relaxation from a 30 μM phenylephrine pre-stimulation stress level in response to cumulative concentrations of acetylcholine (Ach; G and H) is graphed. * indicates p < 0.05 compared to 10% surfactant while # indicates p < 0.05 compared to naïve using repeated measures ANOVA (n = 4 - 7).The p values were derived following the comparison of each concentration response curve across treatment groups using a regression analysis by examining the best-fit values.