Letter: White-cell glutathione reductase in cystic fibrosis.

We have reported that red-cell glutathione reductase (G.R.) activity is increased in 
cystic-fibrosis (C.F.) patients in comparison with age and sex matched controls. 
We have also demonstrated that serum-G.R. activity is significantly greater in 
C.F. than in controls, obligate heterozygotes, and patients with a variety 
of respiratory and immunological diseases. Moreover, serum-G.R. from C.F. patients and 
carriers responds differently from controls after storage or incubation with heparin. 
We have now examined G.R. in white blood-cells (W.B.C.) of C.F. 
patients. The day after collection of samples mean W.B.C.-G.R. activity was 
significantly less in the C.F. group than in carriers and controls. 
No differences in G.R. activity between the groups was apparent after 
4 and 6 days. White-cell G.R. activity apparently is lower in 
C.F. patients than in controls. We cannot rationalise this decrease with 
the increased activity found in C.F. red cells and serum. Nevertheless, 
the differences between C.F. and controls are of greater interest than 
the apparent directional contradiction. The basis for quantatitive enzyme differences is 
very difficult to determine. The simplest explanation is that the initial 
white-cell G.R. differences between C.F. patients on the one hand and 
controls and carriers on the other are secondary to some aspect 
of the disease or its treatment; but there is no evidence 
to support such a conclusion. These results, which reflect altered behaviour 
of G.R. from C.F. patients, suggest to us that G.R. is 
involved in C.F. 