Pulmonary arterial reactivity during induced infection of single lung allografts.
OBJECTIVE
Infection is a major cause of mortality in the first year following single lung transplantation and is a distinct risk factor for the development of obliterative bronchiolitis. However, little is known about changes in pulmonary vascular activity in the setting of infection, which might affect and limit function of the graft. Therefore, the aim of this study was to determine how acute infection altered pulmonary arterial reactivity in single lung allografts. Such information could help to develop better diagnostic and therapeutic targets to improve outcome when grafts become infected.


METHODS
Following single lung transplantation, dogs were immunosuppressed with methylprednisolone acetate, cyclosporine and azathioprine. On postoperative day 5, infection was induced in one group of dogs by endobronchial inoculation of antibiotic resistant Eschericia coli (infection group, n=5); in the second group, the same amount of culture media without bacteria was flushed into the bronchus (control group, n=4). All animals were medicated under the same drug protocol. On postoperative day 8, lungs were removed, reviewed for histological assessment, pulmonary arteries were isolated, cut into rings and suspended for pharmacological characterization in organ chambers.


RESULTS
With acute infections, contractions to phenylephrine and angiotensin-1, but not endothelin-1, were reduced in pulmonary arteries with but not without endothelium. Inhibition of nitric oxide synthase with N(G)-monomethyl-L-arginine, monoacetate salt (L-NMMA) restored these contractions. Endothelium-dependent relaxations to adenosine diphosphate and calcium ionophore, which stimulate release of endothelium-derived nitric oxide by a receptor and non-receptor mediated process, respectively, were not different between groups. Relaxations to nitric oxide also were not different between groups.


CONCLUSIONS
These results suggest that acute infection selectively reduces contractions of pulmonary arteries in part through receptor-mediated release of nitric oxide from the endothelium. Inhibiting nitric oxide during episodes of acute infection may help to improve graft perfusion during episodes of acute infection.
Kim
Hae Kyoon
HK
Mayo Clinic College of Medicine, Rochester, MN 55905, United States.
Rao
Vinay P
VP
Park
Young-Sik
YS
Miller
Virginia M
VM
Tazelaar
Henry D
HD
McGregor
Christopher G A
CG
D000208:Acute Disease; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D016040:Lung Transplantation; D008297:Male; D009894:Opportunistic Infections / Q000503:physiopathology*; D009924:Organ Culture Techniques; D011183:Postoperative Complications / Q000503:physiopathology*; D011651:Pulmonary Artery / Q000187:drug effects / Q000503:physiopathology*; D014661:Vasoconstriction; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation
D007166:Immunosuppressive Agents; D014662:Vasoconstrictor Agents