Effects of various secretagogues on [Ca2+]i in cultured human nasal epithelial cells

Recent studies conducted on cultured canine tracheal cells have suggested that a complex relationship exists between cAMP and Ca2+ in the control of electrolyte secretion. The goal of this study was to determine if the Ca2+ second messenger system functions in a similar fashion in cultured human nasal epithelial cells, a tissue in which control of electrolyte secretion is known to be disrupted in the genetic disease, cystic fibrosis. Human nasal epithelial tissue was obtained as a by-product of surgery and put into monolayer cell culture. After 4-5 days in culture, cells were loaded with fura-2 and intracellular free Ca2+ measured as previously reported. We found that bradykinin increased intracellular free Ca2+ in all cells tested, whereas isoproterenol increased intracellular free Ca2+ in only half the cells tested, suggesting that more than one transporting cell type may be present in this tissue. Epinephrine and prostaglandin E2 had no effect on intracellular free Ca2+. We found that the voltage-sensitive Ca2+ channel blocker verapamil had no effect on the bradykinin-induced change in intracellular free Ca2+. Removal of Ca2+ from the bathing saline only slightly attenuated the increase in intracellular free Ca2+ that resulted from stimulation with bradykinin. We conclude that the source of the increased intracellular free Ca2+, observed during stimulation with secretagogues, was primarily intracellular stores.