Decreased systemic bioavailability of L-arginine in patients with cystic fibrosis.

Background: L-arginine is the common substrate for nitric oxide synthases and arginases. Increased arginase levels in the blood of patients with cystic fibrosis may result in L-arginine deficiency and thereby contribute to low airway nitric oxide formation and impaired pulmonary function.

Methods: Plasma amino acid and arginase levels were studied in ten patients with cystic fibrosis before and after 14 days of antibiotic treatment for pulmonary exacerbation.

Increased arginase activity in cystic fibrosis airways.

Rationale: Airway nitric oxide concentrations are reduced in cystic fibrosis (CF). Arginases compete for L-arginine, the substrate of nitric oxide synthesis.

Objectives: We hypothesized that increased arginase activity may be one factor contributing to nitric oxide deficiency in CF.