Cystic fibrosis. In vitro and in vivo studies on the biochemical background to the pathogenesis.

Cystic fibrosis (CF) is the most common severe, autosomal recessive disease in Caucasians. The main clinical symptoms are all related to exocrine gland disturbances and include obstructive lung disease, pancreatic insufficiency and increased sweat electrolytes. In the present investigation fibroblasts from CF homozygotes were studied by X-ray microanalysis and were shown to have an increased calcium and a decreased sodium content, compared with fibroblasts from controls. The calcium increase was not specific for CF, since it was also found in fibroblasts from trisomy patients. The calcium abnormality could be corrected without any effect on the sodium level by treatment of CF cells with medium conditioned by normal cells. When normal cells were treated with medium conditioned by CF cells, the intracellular sodium level decreased without changes in the calcium level. Acid hydrolases were quantitatively increased in serum from CF patients but no qualitative differences, neither in thermal stability nor in isoelectric focusing patterns were found. Neither was any defect observed in the recognition marker of the hydrolases released from CF fibroblasts. CF homozygotes and heterozygotes had increased concentrations of lactate and electrolytes and increased activities of ribonuclease in their saliva and urine. The salivary concentration of protein was also elevated. When healthy controls were submitted to intensive maximal (anaerobic) exercise on a bicycle ergometer their salivary contents of lactate, ribonuclease, protein and electrolytes increased. Their saliva thus became more like that in CF patients. Indications of abnormal handling of a load dose of sucrose were found in both homozygotes and heterozygotes. Greater increases in the salivary concentrations of both glucose and lactate, but also a more rapid clearance of these metabolites were noted after the sucrose intake. Ingestion of sucrose also caused a normalization (decrease) of the salivary electrolyte content in homozygotes and heterozygotes. Evidence was thus produced to indicate a disturbance in the metabolism of carbohydrates and energy in cystic fibrosis, and it is speculated that such a disturbance might be of importance for the pathogenesis of this disease.