Vasodilatory action mechanisms of apigenin isolated from Apium graveolens in rat thoracic aorta

• Published in: Biochimica et biophysica acta Vol. 1115; no. 1; pp. 69 - 74
• Main Authors: Ko, Feng-Nien, Huang, Tur-Fu, Teng, Che-Ming
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 14.11.1991; Elsevier
• Subjects: A. graveolens; Animals; Aorta, Thoracic - drug effects; Aorta, Thoracic - physiology; Apigenin; Biological and medical sciences; Blood vessels and receptors; Caffeine - pharmacology; Calcium - pharmacology; Calcium influx; Calcium Radioisotopes - metabolism; Chamomile; Cyclic AMP - metabolism; Cyclic GMP - metabolism; Female; Flavonoids - isolation & purification; Flavonoids - pharmacology; Fundamental and applied biological sciences. Psychology; Inositol Phosphates - metabolism; Male; Muscle Contraction - drug effects; Muscle, Smooth, Vascular - drug effects; Norepinephrine - pharmacology; Oils, Volatile - isolation & purification; Oils, Volatile - pharmacology; Plants, Medicinal - chemistry; Potassium - pharmacology; Rat aorta; Rats; Rats, Inbred Strains; Vasodilator Agents - isolation & purification; Vasodilator Agents - pharmacology; Vasorelaxation; Vertebrates: cardiovascular system; Rat aorta; norepinephrine; Apigenin; ACh; NE; acetylcholine; Vasorelaxation; A. graveolens; Calcium influx; Calcium; Rat; Rodentia; Cyclic AMP; 3',5'-GMP; Ionic channel; Muscle contraction; Vasodilation; Thoracic aorta; Vertebrata; Mammalia; Norepinephrine; Mechanism of action
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/0304-4165(91)90013-7

The effect of apigenin, isolated from Apium graveolens, on the contraction of rat thoracic aorta was studied. Apigenin inhibited the contraction of aortic rings caused by cumulative concentrations of calcium (0.03–3 mM) in high potassium (60 mM) medium, with an IC 50 of about 48 μM. After pretreatment it also inhibited norepinephrine (NE, 3 μM)-induced phasic and tonic contraction in a concentration (35–140 μM)-dependent manner with an IC 50 of 63 μM. At the plateau of NE-induced tonic contraction, addition of apigenin caused relaxation. This relaxing effect of apigenin was not antagonized by indomethacin (20 μM) or methylene blue (50 μM), and still existed in endothelial denuded rat aorta or in the presence of nifedipine (2–100 μM). Neither cAMP nor cGMP levels were changed by apigenin. Both the formation of inositol monophosphate caused by NE and the phasic contraction induced by caffeine in the Ca 2+-free solution were unaffected by apigenin. 45Ca 2+ influx caused by either NE or K + was inhibited by apigenin concentration-dependently. It is concluded that apigenin relaxes rat thoracic aorta mainly by suppressing the Ca 2+ influx through both voltage- and receptor-operated calcium channels.