Relation of anion secretory activity to intracellular Ca 2+ in response to lysylbradykinin and histamine in a cultured human colonic epithelium

Abstract

A cultured human epithelial cell line, Colony 29, has been used to investigate the relation between anion secretion and intracellular Ca 2+ concentration (Ca i) in response to the secretagogues, lysylbradykinin (LBk) and histamine. Anion secretion was measured as short-circuit current (SCC) responses in epithelia cultured on pervious supports. Ca i was measured both in cell suspensions and epithelial monolayers using Fura-2 fluorescence. While it is concluded that raised Ca i is responsible for anion secretion the relationship is complex. For both secretagogues there is a receptor reserve, that is the maximal Ca i increase is greater than that required to cause a maximal secretory response. By examining the interactions between maximally effective concentrations of LBk and histamine it was shown that neither the SCC nor Ca i responses behaved additively. From observations in the absence of external Ca 2+ it was concluded that both secretagogues cause Ca 2+ release from the same intracellular source, but that in normal conditions Ca 2+ derived from intracellular and extracellular sources is responsible for the full effect.