title: Functional localization of adenosine receptor-mediated pathways in the LLC-PK1 renal cell line.
abstract: The functional localization of three adenosine receptor-mediated signal transduction pathways in the LLC-PK1 renal cell line was investigated. LLC-PK1 cells were grown on Millicell-CM filter inserts, which allow for the independent exposure of the apical or basolateral side of a confluent cell monolayer to hormones. Adenosine stimulated inositol phosphate turnover, inhibition of adenosine 3',5'-cyclic monophosphate (cAMP) accumulation (A1 receptor), and stimulation of cAMP accumulation (A2 receptor). Adenosine (10 microM) selectively applied to the basolateral side induced a significant (P < 0.05) increase in inositol phosphates, whereas apical exposure did not. The adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (1 microM), blocked the stimulation of inositol phosphate production in LLC-PK1 cells, provided support for an adenosine receptor-mediated event. When adenosine (30 nM) was selectively applied to the apical side, forskolin-stimulated cAMP levels were not significantly decreased (approximately 8%, P > 0.05). However, adenosine (30 nM) presented to the basolateral side produced a significant decrease (approximately 23%, P < 0.05) in forskolin-stimulated cAMP levels. A high dose (100 microM) of adenosine elicited a significant increase (P < 0.05) in cAMP levels when presented to either the apical or the basolateral cell surface. Adenosine (100 microM) applied to the apical side elicited significantly higher cAMP levels (P < 0.05) than the same dose applied basolaterally. LLC-PK1 cells grown on permeable supports exhibit a polarity of functional responses following activation by adenosine. These data support a topographic separation of the multiple adenosine signaling systems in a renal epithelial cell line.
authors.affiliation: Department of Physiology, Michigan State University, East Lansing 48824.
authors.forename: D G
authors.initials: DG
authors.lastname: LeVier
authors.forename: D E
authors.initials: DE
authors.lastname: McCoy
authors.forename: W S
authors.initials: WS
authors.lastname: Spielman
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D007295:Inositol Phosphates / Q000096:biosynthesis; D007425:Intracellular Membranes / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000502:physiology*; D011983:Receptors, Purinergic / Q000502:physiology*; D015398:Signal Transduction; D013997:Time Factors; D014018:Tissue Distribution; D014970:Xanthines / Q000494:pharmacology
chemical_list: D007295:Inositol Phosphates; D011983:Receptors, Purinergic; D014970:Xanthines; D005576:Colforsin; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000242:Cyclic AMP; D000241:Adenosine; D002118:Calcium