Role of histamine in heartworm extract-induced shock in dogs.
OBJECTIVE
To determine whether heartworm (HW) extract-induced shock in dogs is consistent with anaphylactic shock by examining the role of histamine.


METHODS
6 mixed-breed dogs (3 without and 3 with HW infections) and 4 specific pathogen-free (SPF) Beagles.


METHODS
Four experiments were performed as follows: 1) 6 mixed-breed dogs were treated IV with 2 ml of HW extract, and plasma histamine concentrations were determined; 2) 4 SPF dogs were treated IV with 2 ml of HW extract and examined for shock; 3) sera from 6 dogs of experiment 1 and from 4 SPF dogs of experiment 2 that were obtained before HW extract treatment were tested for heterologous passive cutaneous anaphylaxis (PCA), using rabbits during a sensitization period of 48 to 72 hours; and 4) mast cell degranulation by HW extract was tested, using rat mesentery and canine cultured mast cells.


RESULTS
Experiment 1: 6 dogs developed shock, and plasma histamine concentrations increased significantly from 0.3 +/- 0.2 (mean +/- SD) ng/ml before HW extract treatment to 44.6 +/- 68.9 ng/ml at the onset of shock; experiment 2: all SPF dogs developed shock and had an increase in plasma histamine concentrations; experiment 3: sera from mixed-breed dogs without HW infection and from SPF dogs had negative PCA reactions; experiment 4: HW extract degranulated rat mesentery mast cells and released histamine directly from canine mast cells.


CONCLUSIONS
Results of our study indicate that an unknown mast cell-degranulating substances contained in HW extract may degranulate mast cells directly, consequently releasing histamine that may participate in the onset of shock in HW extract-induced shock in dogs.
Kitoh
K
K
Laboratory of Internal Medicine, Faculty of Agriculture, Gifu University, Japan.
Katoh
H
H
Kitagawa
H
H
Nagase
M
M
Sasaki
N
N
Sasaki
Y
Y
D000707:Anaphylaxis / Q000503:physiopathology / Q000662:veterinary*; D000818:Animals; D001794:Blood Pressure; D004183:Dirofilaria immitis; D004184:Dirofilariasis / Q000503:physiopathology*; D004283:Dog Diseases / Q000469:parasitology / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D006632:Histamine / Q000096:biosynthesis / Q000097:blood / Q000502:physiology*; D007958:Leukocyte Count / Q000662:veterinary; D008297:Male; D008407:Mast Cells / Q000378:metabolism / Q000473:pathology; D010323:Passive Cutaneous Anaphylaxis; D010976:Platelet Count / Q000662:veterinary; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D013047:Specific Pathogen-Free Organisms
D006632:Histamine