Desensitization of P2Y2 receptor-activated transepithelial anion secretion
Desensitization of P2Y receptor-activated anion secretion may limit the usefulness of extracellular nucleotides in secretagogue therapy of epithelial diseases, e.g., cystic fibrosis (CF). To investigate the desensitization process for endogenous P2Y receptors, freshly excised or cultured murine gallbladder epithelia (MGEP) were mounted in Ussing chambers to measure short-circuit current (I(SC)), an index of electrogenic anion secretion. Luminal treatment with nucleotide receptor agonists increased the I(SC) with a potency profile of ATP = UTP > 2-methylthio-ATP >> α,β- methylene-ATP. RT-PCR revealed the expression of P2Y receptor mRNA in the MGEP cells. The desensitization of anion secretion required a 10-min preincubation with the P2Y receptor agonist UTP and increased in a concentration-dependent manner (IC ≃ 10 M). Approximately 40% of the anion secretory response was unaffected by maximal desensitizing concentrations of UTP. Recovery from UTP-induced desensitization was rapid (<10 min) at preincubation concentrations less than the EC (1.9 x 10 M) but required progressively longer time periods at greater concentrations. UTP-induced total inositol phosphate production and intracellular Ca mobilization desensitized with a concentration dependence similar to that of anion secretion. In contrast, maximal anion secretion induced by Ca ionophore ionomycin was unaffected by preincubation with a desensitizing concentration of UTP. It was concluded that 1) desensitization of transepithelial anion secretion stimulated by the P2Y receptor agonist UTP is time and concentration dependent; 2) recovery from desensitization is prolonged (>90 min) at UTP concentrations >10 M; and 3) UTP-induced desensitization occurs before the operation of the anion secretory mechanism. 2 2 2 2 50 50 2 -6 -6 2+ 2+ -5
Bicarbonate secretion, Chloride secretion, Cystic fibrosis, Epithelium, Gallbladder, Mouse, Receptor regulation
Clarke, Lane L., Matthew C. Harline, Miguel A. Otero, Geraldine G. Glover, Richard C. Garrad, Brent Krugh, Nancy M. Walker, Fernando A. González, John T. Turner, and Gary A. Weisman. "Desensitization of P2Y2receptor-activated transepithelial anion secretion." American Journal of Physiology-Cell Physiology 276, no. 4 (1999): C777-C787.
American Journal of Physiology - Cell Physiology