NASAL POTENTIAL DIFFERENCE IN CONGENITAL BILATERAL ABSENCE OF THE VAS-DEFERENS

Congenital bilateral absence of the vas deferens (CBAVD) is supposed t o be due to defective activity of the cystic fibrosis (CF) transmembra ne conductance regulator (CFTR) in the genital tract. With the aim of studying CFTR activity in vivo we measured nasal potential difference (NPD) in a group of CBAVD subjects, who were then compared with normal control subjects and CF patients. Sodium transport, measured under ba sal conditions and after amiloride superinfusion, was normal in almost all CBAVD patients, who had NPD values similar to those of normal con trol subjects. Chloride transport was studied by measuring NPD during perfusion with a chloride-free solution and isoproterenol. Under these circumstances CBAVD patients as a whole showed normal chloride secret ion. However, three subjects with CBAVD had abnormal NPD values. They had either elevated sweat chloride concentrations together with sympto ms of mild CF, or compound heterozygosity (Delta F508/R117H). In concl usion the group of CBAVD patients as a whole presented normal bioelect ric properties of nasal epithelium, suggesting normal CFTR activity. I n a small subgroup NPD was abnormal, suggesting a diagnosis of CF, lat er confirmed by elevated sweat chloride concentrations or positive DNA testing. We suggest that CBAVD patients with altered NPD should under go further clinical follow-up in order to detect possible late complic ations of CF.