Effect of olvanil (N-vanillyl-cis-9-octadecenoamide) on cytosolic Ca²⁺ increase in renal tubular cells

In canine renal tubular cells, effect of olvanil, a presumed cannabinoid and vanilloid receptor modulator, on intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured by using fura-2. Olvanil (5-100 M) caused a rapid and sustained [Ca²⁺]_i rise in a concentration-dependent manner. Olvanil-induced [Ca²⁺]_i rise was prevented by 70 and 90% by removal of extracellular Ca²⁺ and La³⁺, respectively, but was not changed by dihydropyridines, verapamil and diltiazem. In Ca²⁺-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca²⁺-ATPase, caused a monophasic [Ca²⁺]_i rise, after which the increasing effect of olvanil on [Ca²⁺]_i was abolished; also, pretreatment with olvanil partly reduced thapsigargin-induced [Ca²⁺]_i rise. U73122, an inhibitor of phoispholipase C, abrogated ATP-, but partly inhibited olvanil-, induced [Ca²⁺]_i rise. Two cannabinoid receptor antagonists (AM251 and AM281; 5 M) and a vanilloid receptor antagonist (capsazepine; 100 M) did not alter olvanil (50 M)-induced [Ca²⁺]_i rise. These results suggest that olvanil rapidly increases [Ca²⁺]_i in renal tubular cells, by stimulating both extracellular Ca²⁺ influx and intracellular Ca²⁺ release via mechanism(s) independent of stimulation of cannabinoid and vanilloid receptors.