Nitrogen-oxide (NO) plays an important role for blood pressure regulation, renal hemodynamics, and the renal excretion of sodium. NO is synthesized from L-arginine in the vascular endothelium and have a very short half-life in plasma and is therefore very difficult to measure directly.

L-mono-methyl-L-arginine (L-NMMA) is an analogue to L-arginine and a competitive inhibitor of NO, and therefore can be used to study the effect of NO on the circulation. In normal subjects, infusion of L-NMMA will cause an increase in blood pressure, decreased renal plasma-flow, decreased glomerular filtration rate, and a decreased excretion of sodium.

Hypothesis: Patients with obstructive sleep apnea has a decreased activity in the NO-system. This is contributing to the hypertension often seen in these patients. Decreased activity in the NO-system can be revealed by diminished fall in renal hemodynamic and sodium excretion after infusion of L-NMMA.

Inclusion Criteria:

• Obstructive sleep apnea

Exclusion Criteria:

• Drug or alcohol abuse
• Pregnancy
• Disease of the heart, lungs, liver, kidney or endocrine organs
• Cerebral infarction
• Diabetes
• Gastrointestinal disease