CHARACTERIZATION AND REGULATION OF ADENOSINE TRANSPORT IN T84 INTESTINAL EPITHELIAL-CELLS

Adenosine release from mucosal sources during inflammation and ischemi a activates intestinal epithelial Cl- secretion. Previous data suggest that A(2b) receptor-mediated Cl- secretory responses may be dampened by epithelial cell nucleoside scavenging. The present study utilizes i sotopic flux analysis and nucleoside analog binding assays to directly characterize the nucleoside transport system of cultured T84 human in testinal epithelial cells and to explore whether adenosine transport i s regulated by secretory agonists, metabolic inhibition, or phorbol es ter. Uptake of adenosine across the apical membrane displayed characte ristics of simple diffusion. Kinetic analysis of basolateral uptake re vealed a Na+-independent, nitrobenzylthioinosine (NBTI)-sensitive faci litated-diffusion system with low affinity but high capacity for adeno sine. NBTI binding studies indicated a single population of high-affin ity binding sites basolaterally. Neither forskolin, 5'-(N-ethylcarboxa mido)-adenosine, nor metabolic inhibition significantly altered adenos ine transport. However, phorbol 12-myristate 13-acetate significantly reduced both adenosine transport and the number of specific NBTI bindi ng sites, suggesting that transporter number may be decreased through activation of protein kinase C. This basolateral facilitated adenosine transporter may serve a conventional function in nucleoside salvage a nd a novel function as a regulator of adenosine-dependent Cl- secretor y responses and hence diarrheal disorders.