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.
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-PGF1 alpha (a metabolite of prostacyclin) production found in the solution. Afterwards, the time-dependent changes in [Ca2+]i and 6-keto-PGF1 alpha synthesis were compared. Bradykinin (BK, 10(-6) M), angiotensin (Ang) II (10(-7) M) as well as ionomycin (10(-6) M) induced simultaneous increases in [Ca2+]i and 6-keto-PGF1 alpha production. An inhibitor against prostaglandin synthesis, acetylsalicylic acid (ASA, 10(-6) M) abolished BK-induced 6-keto-PGF1 alpha synthesis, whereas ASA did not affect the increase in [Ca2+]i. BK-induced increases in [Ca2+]i and 6-keto-PGF1 alpha production occurred in a dose-dependent manner and the half-maximal response was observed at the same concentration of BK (10(-7) M). 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.
Takeuchi
K
K
Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Abe
K
K
Maeyama
K
K
Sato
M
M
Yasujima
M
M
Watanabe
T
T
Yoshinaga
K
K
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000008:administration & dosage / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D011453:Prostaglandins / Q000096:biosynthesis*; D010738:Type C Phospholipases / Q000378:metabolism
D011453:Prostaglandins; D000804:Angiotensin II; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D001920:Bradykinin; D002118:Calcium