Impact of different chloride and glucose solutions on nasal potential difference

The nasal potential difference (nasal PD) technique can provide useful diagnostic information and can be used to assess the physiological effect of new treatments for cystic fibrosis (CF). In preparation for multi center trials of new CF treatments, many groups worldwide have sought to standardize the protocol, but subtle differences in solution composition remain. This article has compared the effect of different chloride and glucose concentrations on the PD.

Following pre-treatment with amiloride to block sodium absorption, the effect of 0 mM versus 6 mM chloride was compared in six non-CF and six CF subjects. In a separate series of experiments, the effect of glucose on baseline PD was examined in the range of 0-20 mM.

Following amiloride pre-treatment, the change from 6 to 0 mM chloride increased the PD by approximately 2 mV in the non-CF subjects; the reverse protocol decreased PD by a similar amount. As expected, little change in PD occurred in the CF subjects. Changing the glucose concentration between 0, 10, and 20 mM had little effect on nasal PD in non-CF and CF subjects.

The use of 0 mM chloride gives responses in the non-CF subjects, which are approximately 2 mV greater than protocols which use low (6 mM) chloride. Different glucose concentrations appear to exert little effect on baseline PD, suggesting that electrogenic glucose transport plays a limited role in airway transport at rest.