Influence of cellular incorporation of n-3 eicosapentaenoic acid on intracellular Ca2+ concentration and membrane potential in vascular smooth muscle cells

• Published in: Atherosclerosis Vol. 138; no. 1; pp. 117 - 127
• Main Authors: ASANO, M, NAKAJIMA, T, YAMASHITA, K, OKUDA, Y, HAZAMA, H, IWASAWA, K, TOMARU, T, OMATA, M, SOMA, M, ASAKURA, Y, MIZUTANI, M, SUZUKI, S
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01-05-1998
• Subjects: Animals; Aorta - cytology; Aorta - metabolism; Aorta - physiology; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Calcium - metabolism; Cardiology. Vascular system; Cell Movement - drug effects; Eicosapentaenoic Acid - metabolism; Fatty Acids - metabolism; Fatty Acids, Unsaturated - pharmacology; Intracellular Membranes - metabolism; Medical sciences; Membrane Potentials - physiology; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - metabolism; Muscle, Smooth, Vascular - physiology; Osmolar Concentration; Rats; Time Factors; Rat; Rodentia; Polyunsaturated fatty acid; Cardiovascular disease; Smooth muscle; Vascular disease; Vertebrata; Mammalia; Calcium ion; Diet therapy; Animal; Blood vessel; Atherosclerosis; Intracellular; Membrane potential; Eicosapentaenoic acid
• ISSN: 0021-9150; 1879-1484
• DOI: 10.1016/s0021-9150(98)00010-0

Long-term treatment with n-3 eicosapentaenoic acid (EPA) has been shown to exert hypotensive effects and have beneficial effects on atherosclerosis. To elucidate one of the underlying mechanisms of these effects, intracellular calcium concentration [Ca2+]i, and resting membrane potential were measured in rat vascular smooth muscle cells (A7r5 cell) treated with EPA, using Ca2+-sensitive dye fura-2 AM and the patch clamp technique. The alterations in fatty acid compositions of phospholipids and cell migration after treatment with EPA (30 microM) for 6 h-7 days were also examined. After treating cells with EPA, the EPA and DPA (docosapentaenoic acid) content of the phospholipid fraction (mol.%) increased in a time-dependent manner. Alternatively, arachidonic acid (AA) decreased, and then the ratio of EPA and AA (EPA/AA) increased significantly. The resting [Ca2+]i decreased from 170 +/- 46 nM (n = 16) in control cells to 123 +/- 29 nM (n = 16) in cells treated with EPA (30 microM) for 7 days. Vasopressin (100 nM), endothelin-1 (100 nM) and platelet-derived growth factor (PDGF 5 ng/ml) evoked an initial peak of [Ca2+]i, followed by a smaller sustained rise of [Ca2+]i in the presence of extracellular Ca2+. In EPA-treated cells, both the peak and the sustained rise of [Ca2+]i induced by these agonists decreased in comparison to the control cells. EPA treatment also decreased the transient [Ca2+]i rise evoked by these agonists in the absence of extracellular Ca2+. Under the current clamp condition, resting membrane potential was significantly higher in EPA-treated cells (-49.8 +/- 10.4 mV, n = 41) than in control cells (-44.6 +/- 7.4 mV, n = 41, P < 0.05), and the input resistance of the cell was lower in EPA-treated cells, while cell size and capacitance were not statistically different. In addition, long-term treatment with EPA for 7 days significantly inhibited PDGF-induced cell migration. These results suggest that cellular incorporation of n-3 eicosapentaenoic acid attenuates intracellular mechanisms related to changes of [Ca2+]i and affects membrane potential, thereby inhibiting migration of vascular smooth muscle cells. These actions of EPA may contribute to its vasorelaxant and antiatherosclerotic effects.