Exhaled oral and nasal nitric oxide during L-arginine infusion in preeclampsia

Objective: To determine the effects of the nitric oxide (NO) precursor L-arginine on the airway NO concentration in patients with preeclampsia. Methods: NO was measured by a noninvasive chemiluminescence technique in air sampled directly from nasal and oral cavities during expiration before and during L-arginine infusion in 9 preeclamptic and 10 control pregnancies. Maternal blood pressure and heart rate were simultaneously recorded, and blood was sampled for analyses of cyclic guanosine monophosphate (cGMP) and nitrate. Results: Basal nasal and orally exhaled NO and the increment in nasal NO concentration during L-arginine infusion were similar in both groups. Basal plasma and platelet cGMP concentrations were similar in both groups. Following L-arginine infusion, plasma cGMP levels were significantly higher in preeclamptics (p < 0.01), while platelet cGMP was unaffected in both groups. Basal plasma nitrate was significantly higher in preeclamptics (p < 0.01), and this difference was not altered following infusion. Blood pressure and heart rate remained unaffected by the procedure in both groups. Conclusions: Blood pressure did not decrease in the preeclamptics following L-arginine infusion, despite a significant increase in nasal NO sampled during breathhold and a concomitant increase in plasma cGMP, possibly reflecting an endogenous NO production. These results do not support the idea of a generalized decrease in NO production being a major cause of hypertension in preeclampsia.