| Abstrakt: |
Hydrogen peroxide (H2O2) caused a transient contraction in endothelium‐intact (E+) and ‐denuded (E−) mesenteric arteries (MA) from 8 – 10‐month‐old spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto rats (WKY) in a concentration‐dependent manner (10−5Mto 10−3M).The contraction to H2O2in MA (E+ or E−) was greater in SHR than in WKY. Removal of endothelium potentiated the contraction to H2O2in WKY but not in SHR. Tachyphylaxis to H2O2was less prominent in SHR than in WKY.The contraction of aorta to H2O2(5×10−4M), expressed as a percentage of 80 mMKCl‐induced contraction, was approximately half of that found in the MA. A greater contraction was found in E+ but not E− SHR aortic rings.The contraction of MA to H2O2(5×10−4M) was greatly inhibited by SQ 29548 and ICI 192605 (thromboxane A2(TXA2)/prostaglandin H2receptor antagonists), quinacrine (a phospholipase A2(PLA2) inhibitor), indomethacin and diclofenac (cyclooxygenase (COX) inhibitors), and furegrelate (a TXA2synthase inhibitor).Production of thromboxane B2induced by H2O2(5×10−4M) was greater in SHR MA than in WKY, and was inhibited by quinacrine, indomethacin and diclofenac, and furegrelate, but not by SQ 29584 and ICI 192605.These results suggested (1) that SHR MA exhibits a higher contraction involving an increased smooth muscle reactivity and less tachyphylaxis to H2O2than WKY; (2) that a greater production of TXA2through activation of PLA2‐COX‐TXA2synthase pathway appeared to be responsible for the enhanced contraction in SHR MA. The enhanced vascular response to H2O2may be related to hypertension in SHR. |
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