[Effects of nitric oxide on pleural lymphatic stomata and lymphatic drainage in the rat]

To investigate the effects of nitric oxide (NO) on the pleural lymphatic stomata and lymph absorption from the pleural cavity, the NOS (nitric oxide synthase) inhibitor N(omega)-nitro-L-arginine-methyl-ester (L-NAME) and the NO donor isosorbide dinitrate (ISDN) were injected into the peritoneal cavity of the rats respectively. Trypan blue was used as a tracer. Then the concentrations of NO and trypan blue in the blood serum were measured, and the ultrastructural changes in pleural lymphatic stomata were observed under a scanning electron microscope (SEM) and studied by a computer image processing system attached to SEM. It turned out that the concentration of NO in the serum was 49.34+/-18.47 micromol/L, and the area and density of the pleural lymphatic stomata were 6.80+/-1.13 microm(2) and 170.24+/-66.60 /0.1 mm(2) respectively in the NO donor group. The concentration of NO reduced to 17.72+/-6.58 micromol/L, and the area and density of the pleural lymphatic stomata were 5.72+/-1.54 microm(2) and 61.71+/-12.73/0.1 mm(2) in the NOS inhibitor group. We found that the area and density of the pleural lymphatic stomata were positively correlated with the NO quantity. After the tracer was injected into the pleural cavity, the NO donor group exhibited a higher trypan blue concentration than the control group. The ability of the pleura to absorb trypan blue was enhanced because of the large opening of the stomata. It is suggested that NO can increase lymph absorption of the pleura by relaxing pleural lymphatic stomata.