Role of platelet-activating factor in alveolar septal injury associated with experimentally induced pneumonic pasteurellosis in calves.
OBJECTIVE
To determine whether platelet-activating factor (PAF) is involved in acute lung microvascular injury associated with pneumonic pasteurellosis in calves.


METHODS
15 healthy 2- to 4-week-old male Holstein calves.


METHODS
Calves were anesthetized and inoculated intrabronchially with saline (0.9% NaCl) solution (n = 5) or 1x10(9) Pasteurella haemolytica organisms (n = 10). Of the 10 calves inoculated with P haemolytica, 5 also were treated with WEB 2086, a potent inhibitor of PAF, and 5 were treated with vehicle. Blood and bronchoalveolar lavage samples were collected before and 1, 2, 4, and 6 hours after inoculation of P. haemolytica. Blood samples were analyzed to evaluate total number and differential counts of leukocytes, dilute whole-blood leukocyte deformability, size of neutrophils, and neutrophil CD11b expression. Bronchoalveolar lavage samples were analyzed for total number and differential counts of nucleated cells, total protein concentration, and hemoglobin concentration. Size and gross and histologic appearance of lung lesions also was determined.


RESULTS
Treatment of calves with WEB 2086 reduced size of lung lesions, attenuated the increase in microvascular permeability, and reduced neutrophil infiltration in the first 4 hours after inoculation. Treatment with WEB 2086 also attenuated a decrease in leukocyte deformability, increase in size of neutrophils, and CD11b expression by circulating neutrophils.


CONCLUSIONS
It appears that PAF is a major mediator for altered lung microvascular permeability and activation of circulating neutrophils in the first 4 hours after onset of pneumonic pasteurellosis in calves.
McClenahan
D J
DJ
Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, St. Paul 55108, USA.
Fagliari
J J
JJ
Evanson
O A
OA
Weiss
D J
DJ
D000818:Animals; D001381:Azepines / Q000494:pharmacology / Q000627:therapeutic use; D018893:Bronchoalveolar Lavage / Q000662:veterinary; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000382:microbiology; D002417:Cattle; D005434:Flow Cytometry / Q000662:veterinary; D006454:Hemoglobins / Q000032:analysis; D007428:Intradermal Tests / Q000662:veterinary; D007958:Leukocyte Count / Q000662:veterinary; D008168:Lung / Q000473:pathology; D016177:Macrophage-1 Antigen / Q000097:blood; D008297:Male; D016978:Mannheimia haemolytica / Q000187:drug effects / Q000254:growth & development*; D009504:Neutrophils / Q000737:chemistry; D012766:Pasteurellosis, Pneumonic / Q000188:drug therapy / Q000473:pathology*; D010972:Platelet Activating Factor / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011650:Pulmonary Alveoli / Q000382:microbiology / Q000473:pathology*; D014230:Triazoles / Q000494:pharmacology / Q000627:therapeutic use
D001381:Azepines; D006454:Hemoglobins; D016177:Macrophage-1 Antigen; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D014230:Triazoles; C052518:WEB 2086