Exp Mol Med.  1998 Sep;30(3):151-158.

Caffeine causes glycerophosphorylcholine accumulation through ryanodine-inhibitable increase of cellular calcium and activation of phospholipase A2 in cultured MDCK cells

• Kim DK
• Jung KY

Abstract

Glycerophosphrylocholine (GPC) is a renal medullary compatible organic osmolyte that is derived from choline via phosphatidylcholine, which is catalyzed in part by phospholipase A2 (PLA2) and its degradation by GPC: choline phosphodiesterase (GPC: choline PDE). We found that caffeine elevated intracellular free calcium ([Ca2+]i) and GPC level in cultured MDCK cells, canine kidney epithelial cells, and propose a possible biochemical mechanism. When MDCK cells were incubated for 3 h with 1 to 10 mM caffeine, cellular GPC was elevated in a dose-dependent manner, and this occurred independently of the extracellular osmolality. Caffeine stimulated the rate of [14C]choline incorporation into [14C]GPC and PLA2 activity. Whereas, GPC: choline PDE activity was accompanied by less of increase. These enzyme changes demonstrate the increased net synthesis of MDCK GPC. In order to identify what triggers the PLA2 activation, [Ca2+]i was measured by using a fluorescence dye, Fura-2. Caffeine (10 mM) resulted in a typical transient increase in MDCK [Ca2+]i concentration, and this increase was greatly inhibited by pretreatment of MDCK cells with 10 mM ryanodine for 5 min. Ryanodine (10 mM) also inhibited the caffeine-induced stimulation of PLA2 activity. These findings provide the first evidence that caffeine in MDCK cells causes a ryanodine-inhibitable increase of [Ca2+]i and PLA2 activity, resulting in cellular GPC accumulation.

Keyword

caffeine; [Ca2+]i; glycerophosphorylcholine,; phospholipase A2; MDCK

MeSH Terms

Animal
Caffeine/pharmacology*
Calcium/metabolism*
Carbon Radioisotopes
Cell Line
Choline/metabolism
Dogs
Glycerylphosphorylcholine/metabolism*
Kidney/cytology
Phospholipases A/metabolism*
Phospholipases A/drug effects
Phospholipases A/antagonists & inhibitors
Phosphoric Diester Hydrolases/metabolism
Phosphoric Diester Hydrolases/drug effects
Ryanodine/pharmacology*
Ryanodine/metabolism