MEMBRANE-RESTRICTED REGULATION OF CA2+ RELEASE AND INFLUX IN POLARIZED EPITHELIA

EPITHELIAL cells exist in a complex setting in which responses to muco sal or serosal environments are mediated by receptors expressed on spe cialized cellular domains, such as apical versus basolateral cell memb ranes, We investigated whether airway epithelia can react selectively through G-protein-coupled receptors to stimuli in the mucosal or seros al environments by measuring inositol phosphate and intracellular Ca2 responses in polarized human nasal epithelial monolayers, We report h ere that unilateral ATP (10(-4) M) administration stimulated P-2 purin oceptors and tapped pools of intracellular Ca2+ associated with the pl asma membrane ipsilateral but not contralateral to stimulated receptor s. Similarly, activation of plasma membrane Ca2+ influx by ATP was con fined to the membrane ipsilateral to receptor stimulation. These findi ngs demonstrate that polarized epithelia restrict P-2 receptor-mediate d responses to a single domain of the cell, reflecting membrane-specif ic generation and catabolism of inositol phosphates and confinement of calcium influx regulation to the membrane ipsilateral to the stimulat ed receptors.