Ultrastructural studies on cultured fibroblasts from patients with cystic fibrosis.

The ultrastructure of cultured fibroblasts of patients with cystic fibrosis (CF) was investigated and compared with control cultures. CF-fibroblasts showed a significantly increased number of pinocytotic vesicles along the plasma membrane. Other differences in ultrastructure between CF-fibroblasts and controls could not be observed. Cytochemical localisation of calcium was studied after fixation in the presence of oxalate. In CF-fibroblasts, oxalate precipitates (presumably indicating the presence of calcium) were found in the cytoplasm, often associated with membranes of the endoplasmic reticulum and Golgi vesicles, and in association with nuclear membrane and plasma membrane. In control fibroblasts, oxalate precipitates were scarce. The results are in accordance with earlier findings of elevated calcium in fibroblasts from CF-patients, and point to a localisation of at least part of the excess calcium in the cytoplasm and microsomal fraction.