In this study we investigated the role of the adenosine analogue 2-chloroadenosine (CAD) in the regulation of protein kinase C (PKC) in porcine coronary artery. Arterial rings were contracted with endothelin-1 (ET-1; 10(-10) to 10(-7) M) and phorbol 12,13-dibutyrate (PDBu; 10(-7) M) after incubating them for 1 and 2 days with PDBu (200 nM) in the presence and absence of CAD (10(-4) M). Chronic exposure to PDBu alone attenuated ET-1-induced contractions, while inclusion of CAD during incubation protected against the PDBu-induced blunting of ET-1-induced contraction. Similarly, PDBu (10(-7) M)-induced contraction of the arterial rings was attenuated upon chronic incubation with PDBu, and once again, inclusion of CAD showed an improved response to PDBu-induced contraction when compared with PDBu alone. Incubation with PDBu (200 nM) for 20 min caused the PKC translocation from cytosol to membrane, whereas CAD totally blocked this translocation. Chronic (1 and 2 days) incubation with PDBu caused a substantial depletion of PKC activities in cytosol and membrane. The presence of CAD protected the PDBu-induced depletion of PKC in both cytosol and membrane. To replete PKC, after incubation with the drugs, the arteries were incubated in the absence of drugs for another 2 days. Arteries incubated with PDBu in the presence and absence of CAD recovered significantly in their response to ET-1 as well as PDBu. These results indicate that CAD protects against the PDBu-induced activation and depletion of PKC in porcine coronary artery.
Exogenous sphingosine 1-phosphate and sphingosylphosphorylcholine do not stimulate phospholipase D in C6 glioma cells.
