STIMULATION OF SECRETORY ACTIVITY BY CF FACTO

Exposure of hamster tracheal explants to whole cystic fibrosis serum (CFS) or fractionated serum components for various lengths of time caused the explusion of mucin droplets from cells lining the luminal surface of tracheal rings, as visualized by scanning and transmission electron microscopy. The effect was not observed with normal serum (NHS), fetal calf serum (FCS), or bronchitic serum (BHS). Epithelial cells were isolated from hamster tracheae (HTE cells) and exposure of log-phase {('14)C}threonine labeled HTE cells to whole serum or partially purified serum proteins from CF patients resulted in an increase in the rate of protein secretion over that elicited by serum proteins from normal individuals, while serum from heterozygotes was intermediate in its effect. Concomitantly these cells took up calcium ion reaching a maximum at 30 min. whose amplitude was dependent upon serum concentration. Chelation of F12 medium in the presence of CFS with 4mM EGTA resulted in a 96% decrease in ('45)Ca('2+) uptake and also caused a decrease in secretion to the basal normal serum response. Treatment of the cells with ionophore A23187 (10 (mu)g/ml) promoted HTE cell calcium uptake and resulted in a maximum CFS-like response in either the presence of any serum, with respect to cellular secretion. Using verapamil at various concentrations, 10('-8)M inhibited ('45)Ca('2+) uptake stimulated by CFS approximately 50%, and cellular secretion was brought to normal levels. Secreted proteins precipitated with alcian blue were resolved by SDS-PAGE followed by fluorography. It was found that several proteins were constitutively secreted by HTE cells in the presence of NHS, while CF factor apparently induced the secretion of specific proteins. A model is presented in which a CF serum factor simulates HTE cells by receptor-mediated opening of a calcium channel. It appears that extracellular calcium stimulates the secretion of 'mucin-like' glycoproteins and that this activity is different from the ciliary-inhibitory activity previously reported for CF factor.