Simultaneous Measurements of Cytosolic Free Calcium Level and Prostaglandin Synthesis Reveal a Correlation between Them in Perfused Monolayer of Cultured Rat Vascular Smooth Muscle Cells: Effects of Bradykinin and Angiotensin II.

TAKEUCHI, K., ABE, K., MAEYAMA, K., SATO, M., YASUJIMA, M., WATANABE, T. and YOSHINAGA, K. Simultaneous Measurements of Cytosolic Free Calcium Level and Prostaglandin Synthesis Reveal a Correlation between Them in Perfused Monolayer of Cultured Rat Vascular Smooth Muscle Cells: Effects of Bradykinin and Angiotensin II. Tohoku J. Exp. Med., 1991, 165 (3), 183-192-The level of cytosolic free calcium ([Ca2+]I) and the production rate of prostacyclin were simultaneously measured in perfused monolayers of cultured vascular smooth muscle (VSM) cells. After loading of fura-2 (a fluorescent calcium indicator), the monolayer of VSM cells (cultured on a cover glass) was fixed in the perfusion cuvette and the cuvette was placed in a fluorometer to monitor the change in [Ca2+]i. The monolayer was perfused and the fractionated perfusion solution was collected to determine 6-keto-PGF1a (a metabolite of prostacyclin) production found in the solution. Afterwards, the time-dependent changes in [Ca2+]i and 6-keto-PGF1a synthesis were compared. Bradykinin (BK, 10-6M), angiotensin (Ang) II (10-7M) as well as ionomycin (10-6M) induced simultaneous increases in [Ca2+]i and 6-keto-PGF1a production. An inhibitor against prostaglandin synthesis, acetylsalicylic acid (ASA, 10-6M) abolished BK-induced 6-keto-PGF1a synthesis, whereas ASA did not affect the increase in [Ca2+]i. BK-induced increases in [Ca2+]i and 6-keto-PGF1a production occurred in a dose-dependent manner and the half maximal response was observed at the same concentration of BK (10-7M). These results indicate that an increase in [Ca2+]i is closely associated with BK as well as AngII-induced prostacyclin synthesis. It is suggested that an increase in [Ca2+]i plays a prior role in prostacyclin synthesis. Thus, an interaction between phospholipase A2 (prostaglandin synthesis) and phospholipase C (inositol trisphosphate-Ca2+mobilization) is suggested.