Beta-adrenergic sweat responses in cystic fibrosis heterozygotes with and without the delta F508 allele.

Abstract

Cystic fibrosis (CF) causes early death for most homozygotes, yet has a carrier frequency among Caucasians of about 4-5%, suggesting a heterozygote advantage. The major defect in the CF gene is a three-base deletion leading to loss of a phenylalanine residue at position 508 (delta F508) that accounts for about 68% of CF alleles in the North American population; the remaining 32% appears to consist of a large assortment of mutations. Sweat secretion in response to beta-adrenergic stimulation is completely lacking in CF homozygotes and is reduced to 1/2 normal in heterozygotes. To determine if this secretory process is affected by different CF alleles, we used the polymerase chain reaction technique with DNA obtained from peripheral leukocytes to determine retrospectively the presence or absence of the delta F508 allele in 20 CF heterozygotes for whom sweat responses to beta-adrenergic stimulation had previously been determined. Twelve of 20 subjects (60%) were positive for the delta F508 mutation. The variance in sweat responses was not reduced in the delta F508 group relative to the non-delta F508 group, but a gender/allele interaction was noted.