title: Effects of cystic fibrosis serum on calcium influx and secretion using isolated tracheal epithelial cells.
abstract: Hamster trachea epithelial (HTE) cells were shown to respond to 20% cystic fibrosis serum (CFS) by secreting twice as much protein as in the presence of 20% normal human serum (NHS). Serum from obligate heterozygotes (HHS) produced an intermediate effect. A peak of Ca2+ entry into the HTE cells occurred about 30 min after exposure to 20% CFS, followed by a slow decline to basal levels. In contrast, 20% NHS did not cause an influx of Ca2+ and HHS produced an influx to about half that of CFS. Increasing concentrations (5-30%) of pooled NHS had no effect on HTE cell Ca2+ uptake or secretion, but pooled CFS and HHS caused progressive increases in Ca2+ influx and protein secretion from 10 to 25% sera. The CFS-induced Ca2+ influx and secretion were about twice those of HHS throughout the range of serum concentrations tested, suggesting the presence of a modulatory influence in HHS. When EGTA was used to chelate extracellular Ca2+ in the presence of CFS, Ca2+ influx was prevented and there was no stimulation of secretion. Ionophore A23187 allowed Ca2+ entry into HTE cells in the presence or absence of serum and a heightened level of secretory activity followed. The time course of Ca2+ influx under the influence of CFS was shown to correspond to the efflux of Na+ from the cells. Also verapamil, a Ca2+ channel blocking agent, inhibited CFS-induced Ca2+ influx by 50% at 10(-5)M and prevented secretion. Thus, it appears that CFS, but not NHS, contains an agent which stimulates Ca2+ uptake into HTE cells by means of a Ca2+ channel and/or Na+-Ca2+ exchange mechanism, and that increased intracellular Ca2+ levels then trigger secretion. The intermediate HTE cell response to HHS suggests that half of the CFS stimulatory agent is present as would be expected in a gene dose effect, lending support for a genetic basis for CF.
mesh_terms: D000293:Adolescent; D000328:Adult; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000097:blood*; D004533:Egtazic Acid / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007223:Infant; D012964:Sodium / Q000378:metabolism; D014132:Trachea / Q000378:metabolism* / Q000473:pathology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002132:Calcium Radioisotopes; D000001:Calcimycin; D004533:Egtazic Acid; D012964:Sodium; D014700:Verapamil; D002118:Calcium