Letter: Uptake of 35S-heparin by lymphocytes from cystic-fibrosis patients.

In 1969 Danes and Bearn proposed that the metachromasia noted in short-term 
white-blood-cell cultures from both cystic fibrosis (C.F.) homozygotes and heterozygotes probably 
reflected uptake of heparin from the culture-medium by pinocytosis and not, 
as in the genetic mucopolysaccharidoses, stored mucopolysaccharides. This hypothesis was recently 
confirmed by Robertson et al. Using 35S-heparin they demonstrated an increased 
uptake of heparin in short-term C.F. white-blood-cell cultures which corresponded to 
the observations made on the basis of staining. However, as mentioned 
in 1971 by Bafalluy et al., any white blood-cell in culture 
can be overloaded with heparin. As the processes involved in endocytosis 
and exocytosis probably are inconstant within one cell and certainly in 
different cell types, standardisation of cytoplasmic retention of heparin may not 
be possible in order to eliminate the partial overlap between normals, 
C.F. homozygotes and obligatory heterozygotes observed by Robertson et al. This 
report on 35S-heparin again raised the question of the significance of 
cellular mucopolysaccharides in cystic fibrosis. The relevance of mucopolysaccharides in the 
C.F. cultured cell is still unclear. Between 1968 and 1970 the 
mucopolysaccharide content of the cultured fibroblast was reported as normal and 
variable. 