Abnormal Erythrocyte Sodium Transport in Cystic Fibrosis (CF)

Abstract

To further explore the recently reported erythrocyte cation transport defect in cystic fibrosis (CF) patients and their parents [BALFER et al., Science, 00:…, 1968], we have measured sodium (Na) content and the major components of Na outflux in erythrocytes from 21 normal young adults, 22 CF patients (ages 7–27), and 20 obligate heterozygotes.

Ma content of red cells from patients and heterozygotes was normal. Of the various components of Na outflux measured, there was no difference between heterozygotes and their normal male or femal counter parts.

Of the major components of Na outflux, that portion sensitive to ouabain (0—) was normal in all CF groups. Abnormalities of Na outflux in CF were primarily due to that portion which was insensitive to ouabain and sensitive to ethacrynic acid (0–/E+). 0–/E+ fractional outflux was decreased in CF males of all ages (0.027±0.02/h) relative to male controls (0.051±0.02). 0–/E+ was decreased in 7 CF females over the age of 16 (0.012±0.005) compared to female controls (0.023±0.01). However, in the 4 CF females under 16, 0–/E+ outflux (0.057±0.003) was greater than that of older CF females.

The normal data from heterozygotes indicate that erythrocyte Na outflux cannot be used as a ‘gentic marker’ for CF. These data document altered cation transport in non-exocrine tissue from males and older females with CF. Furthermore, this abnormality does not simply reflect a general alteration of erythrocyte cation transport, but is localized to a single specific component of Na outflux, which has a characteristic requirement for metabolic substrates as well as distinctive kinetic parameters. Studies of this transport system in other tissue from patients with CF may permit a characterization of the disease at the molecular level.

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