Contraction of Arterial Smooth Muscle of Normotensive and Spontaneously Hypertensive Rats by Manganese(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP)

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Manganese(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP), which has been known as a cell permeable superoxide dismutase mimetic, induced concentration-dependent contraction in rat carotid artery acting directly on smooth muscle. The contractile action was more prominent in the preparation from stroke-prone spontaneously hypertensive rats (SHRSP) compared with that from Wistar Kyoto rats (WKY). It was abolished by the removal of extracellular Ca²⁺ or the application of verapamil. These results suggest that the MnTMPyP-induced contraction is brought about by Ca²⁺ influx through voltage-dependent Ca²⁺ channels (VDCC) and that the difference in VDCC is the cause of the difference in MnTMPyP action between preparations from WKY and SHRSP.