Oxygen radicals and substance P in perinatal hypoxia-exaggerated, monocrotaline-induced pulmonary hypertension.

Perinatal hypoxia has been observed to cause more aggressive pulmonary hypertension in human. Several mediators such as reactive oxygen species (ROS) and substance P are believed to be crucial in the mechanism of inducing pulmonary hypertension. This study was designed to test whether substance P and ROS play a role in perinatal hypoxia-exaggerated, monocrotaline (MCT)-induced pulmonary hypertension. Normoxic Wistar rats (weighing 258 +/- 9 g, n = 31) were divided into two groups: control (n = 16) and MCT (n = 15). Perinatal hypoxia Wistar rats (weighing 260 +/- 19 g, n = 49) were divided into six groups: Hypoxia (n = 8), Hypoxia+MCT (n = 8), Hypoxia+capsaicin (CP)+MCT (n = 7), Hypoxia+MCT+1,3-dimethyl-2-thiourea (DMTU)(E) (n = 10), Hypoxia+MCT+DMTUL (n = 9), and Hypoxia+MCT+ hexa(sulfobutyl) fullerenes (HSF) (n = 7). Rats in the control group received saline injections. MCT (60 mg/kg, s.c.) was given three weeks prior to the functional examination. Chronic capsaicin pretreatment was performed to deplete substance P. Hydroxyl radical scavenger DMTU (500 mg/kg) was intraperitoneally (i.p.) injected early (DMTUE) or late (DMTUL) after MCT. Antioxidant HSF (10 mg/kg, i.p.) was given once daily for three weeks following MCT. MCT treatment caused significant increases in pulmonary arterial pressure (Ppa) and substance P level in lung tissue in normoxic rats. The MCT-induced increase in pulmonary arterial blood pressure was exaggerated by perinatal hypoxia, but this exaggeration was attenuated by either capsaicin pretreatment or antioxidant administrations. These results suggest that both ROS and substance P are involved in perinatal hypoxia-augmented, MCT-induced pulmonary hypertension.