Effect of adult heartworm (HW) crude extract on isolated canine abdominal aortic strips precontracted with noradrenaline was examined by recording isometric changes in tension. HW extract caused contraction of the aortic strip at a low concentration (LC) and its relaxation at a high concentration (HC). In aortic strips without endothelium, LC extract elicited a contraction similar to that in the strips with endothelium, whereas HC extract failed to produce any relaxation but instead produced a contraction. The relaxing effect of HC extract was blocked after treatment with 300 µM NG-nitro-l-arginine methyl ester hydrochloride, with reversal by additional treatment with 3 mM l-arginine. It was also markedly reduced or abolished after treatment with 3 µM oxyhemoglobin or 1 µM methylene blue. Fractionation of HW extract by high-performance liquid chromatography revealed that the relaxing and contracting activities are due to different substances in the extract. The results indicate that HW extract contains 2 different vasoactive substances, 1 causing contraction of canine abdominal aorta via a direct action on the smooth muscle, and the other its relaxation indirectly by releasing nitric oxide from endothelial cells. These vasoactive substances might play a role in HW extract-induced shock in dogs, and in the pathogenesis of HW infection.
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June 2001
BIOCHEMISTRY-PHYSIOLOGY|
June 01 2001
Relaxing and Contracting Activities of Heartworm Extract on Isolated Canine Abdominal Aorta
KATSUYA KITOH;
KATSUYA KITOH
Laboratory of Internal Medicine, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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AKIKO OKA;
AKIKO OKA
Laboratory of Internal Medicine, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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HITOSHI KITAGAWA;
HITOSHI KITAGAWA
Laboratory of Internal Medicine, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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TOSHIHIRO UNNO;
TOSHIHIRO UNNO
Laboratory of Internal Medicine, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
*Laboratory of Veterinary Pharmacology, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
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SEIICHI KOMORI;
SEIICHI KOMORI
Laboratory of Internal Medicine, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
*Laboratory of Veterinary Pharmacology, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
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YOSHIHIDE SASAKI
YOSHIHIDE SASAKI
Laboratory of Internal Medicine, Division of Veterinary Medicine, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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J Parasitol (2001) 87 (3): 522–526.
Citation
KATSUYA KITOH, AKIKO OKA, HITOSHI KITAGAWA, TOSHIHIRO UNNO, SEIICHI KOMORI, YOSHIHIDE SASAKI; Relaxing and Contracting Activities of Heartworm Extract on Isolated Canine Abdominal Aorta. J Parasitol 1 June 2001; 87 (3): 522–526. doi: https://doi.org/10.1645/0022-3395(2001)087[0522:RACAOH]2.0.CO;2
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