Superoxide dismutase and catalase do not affect the pulmonary hypertensiveresponse to group B streptococcus in the lamb

The purpose of this study was to determine whether treatment with conjugate d antioxidant enzymes could attenuate or abolish pulmonary hypertension ind uced by group B streptococcus (GBS). Lambs, 3-7 d old, were anesthetized an d ventilated. Intravascular catheters were placed in the left ventricle, de scending aorta, right atrium, and pulmonary artery for continuous monitorin g of intravascular pressures. Cardiac output was measured with radiolabeled microspheres. Measurements were obtained at baseline and 15 and 60 min int o a 60-min GBS infusion, and 60 min after GBS was stopped. Blood gas values were held constant and Pao, was maintained >100 mm HE. The control group r eceived saline vehicle only (n = 6), the GBS group received GBS infusion on ly (n = 9), the enzymes (ENZ) group received polyethylene glycol-superoxide dismutase (PEG-SOD) and polyethylene glycol-catalase (PEG-CAT) treatment o nly (n = 6), and the ENZ + GBS group received PEG-SOD and PEGCAT then GBS ( n = 9). Plasma samples were obtained to confirm increased superoxide dismut ase and catalase activities in the groups receiving enzymes. Compared with baseline, pulmonary vascular resistance increased by 119% and 101% at 15 mi n and 87% and 81% at 60 min in the GBS and ENZ + GBS groups, respectively. Sixty minutes after the termination of the GBS infusion, PVR returned to ba seline in the GBS group but did not in the ENZ + GBS group. Enzyme infusion s resulted in at least a ninefold increase in plasma enzyme activities. As opposed to previously published data from endotoxin models, PEG-CAT and PEG -SOD were ineffective in altering the GBS-induced pulmonary hypertensive re sponse in this model. This suggests that acute administration of antioxidan t enzymes may not be effective in ameliorating GBS-induced pulmonary hypert ension.