Effect of heartworm infection on in vitro contractile responses of canine pulmonary artery and vein

Daria S. Maksimowich From the Departments of Physiology (Maksimowich, Mupanomunda, Kaiser) and Microbiology (Williams), Michigan State University, East Lansing, MI 48824-1101.

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Maria Mupanomunda From the Departments of Physiology (Maksimowich, Mupanomunda, Kaiser) and Microbiology (Williams), Michigan State University, East Lansing, MI 48824-1101.

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 MBChB, PhD
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Jeffrey F. Williams From the Departments of Physiology (Maksimowich, Mupanomunda, Kaiser) and Microbiology (Williams), Michigan State University, East Lansing, MI 48824-1101.

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Lana Kaiser From the Departments of Physiology (Maksimowich, Mupanomunda, Kaiser) and Microbiology (Williams), Michigan State University, East Lansing, MI 48824-1101.

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 MD, DVM

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Abstract

Objective

To test the effect of heartworm infection on agonist-induced constriction of canine pulmonary artery and vein in vitro.

Procedure

Cumulative concentration-response relations to norepinephrine, serotonin, histamine, prostaglandin F2α, and the thromboxane A2 analog U-44069 were determined, using isolated rings of pulmonary artery and vein from control and heartworm-infected dogs. To determine the role of endothelial cells in histamine constriction, some rings were denuded of endothelial cells in both artery and vein.

Animals

Noninfected control and heartworm-infected dogs.

Results

There was no difference in constriction response to norepinephrine, serotonin, prostaglandin F2α, or U44069 of pulmonary artery or vein from control or heartworm-infected dogs. Histamine-induced constriction of pulmonary artery from heartworm-infected dogs was not different from control values, however, when endothelial cells were removed from control, but not heartworm-infected pulmonary artery, histamine-induced constriction was enhanced. Histamine-induced constriction of pulmonary vein from heartworm-infected dogs was significantly depressed, compared with that of control pulmonary vein. However, removal of endothelial cells in pulmonary vein from heartworm-infected, but not control dogs significantly increased constriction.

Conclusion

Heartworm infection alters histamine-induced constriction responses of pulmonary artery and vein. These changes may reflect high circulating histamine concentrations in heartworm-infected dogs, compared with that in controls. Increased circulating histamine concentrations in vivo could bring about decreased sensitivity of histamine receptors or decreases in the number of receptors expressed.

Clinical Relevance

Mast cells and histamine may be important factors in altered endothelium-mediated responses associated with heartworm disease. (Am J Vet Res 1997;58:394–397)

Abstract

Objective

To test the effect of heartworm infection on agonist-induced constriction of canine pulmonary artery and vein in vitro.

Procedure

Cumulative concentration-response relations to norepinephrine, serotonin, histamine, prostaglandin F2α, and the thromboxane A2 analog U-44069 were determined, using isolated rings of pulmonary artery and vein from control and heartworm-infected dogs. To determine the role of endothelial cells in histamine constriction, some rings were denuded of endothelial cells in both artery and vein.

Animals

Noninfected control and heartworm-infected dogs.

Results

There was no difference in constriction response to norepinephrine, serotonin, prostaglandin F2α, or U44069 of pulmonary artery or vein from control or heartworm-infected dogs. Histamine-induced constriction of pulmonary artery from heartworm-infected dogs was not different from control values, however, when endothelial cells were removed from control, but not heartworm-infected pulmonary artery, histamine-induced constriction was enhanced. Histamine-induced constriction of pulmonary vein from heartworm-infected dogs was significantly depressed, compared with that of control pulmonary vein. However, removal of endothelial cells in pulmonary vein from heartworm-infected, but not control dogs significantly increased constriction.

Conclusion

Heartworm infection alters histamine-induced constriction responses of pulmonary artery and vein. These changes may reflect high circulating histamine concentrations in heartworm-infected dogs, compared with that in controls. Increased circulating histamine concentrations in vivo could bring about decreased sensitivity of histamine receptors or decreases in the number of receptors expressed.

Clinical Relevance

Mast cells and histamine may be important factors in altered endothelium-mediated responses associated with heartworm disease. (Am J Vet Res 1997;58:394–397)

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