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.
Animals ; Lymphatic System ; physiology ; NG-Nitroarginine Methyl Ester ; pharmacology ; Nitric Oxide ; blood ; Nitric Oxide Synthase ; antagonists & inhibitors ; Peritoneal Stomata ; ultrastructure ; Rats

To study the cell signal transduction mechanism of nitric oxide (NO) on the peritoneal lymphatic stomata and lymph drainage in the rat, cGMP content were measured by a commercially available radioimmunoassay kit, and the [Ca(2+)](i) were observed by a confocal laser scanning microscope in the cultured peritoneal mesothelial cell. Animal experiment was practiced to study the effect of NO-cGMP-Ca(2+) pathway on the lymphatic stomata and lymph absorption. The results showed that: (1) Sper/NO increased cGMP of the rat peritoneal mesothelial cell (RPMC) in a dose-dependent manner (P<0.01) compared to the control group. This effect was blocked by 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) (P<0.05), a specific inhibitor of soluble guanylyl cyclase (sGC). The level of [Ca(2+)](i) in single RPMC decreased by adding Sper/NO (P<0.05). Pretreatment with ODQ for 10 min blocked the Sper/NO-induced decrease in [Ca(2+)](i). L-typed calcium channel blocker nifedipine induced an immediate and marked decrease in [Ca(2+)](i) (P<0.05).. After [Ca(2+)](i) reached a balance again, adding Sper/NO could not change [Ca(2+)](i) (P>0.05). (2) Sper/NO increased the area of the stomata (P<0.01) and the quantity of the tracer in a dose-dependent manner (P<0.05) compared to the control group. Pretreatment with ODQ significantly inhibited Sper/NO-induced change of lymphatic stomata and lymph drainage (P<0.01). Nifedipine increased the opening area of the lymphatic stomata (P< 0.01) and the concentration of absorbed trypan blue of the diaphragm (P<0.05). Sper/NO could not make a further change in the samples pretreated by nifedipine (P> 0.05). The results indicate that NO can decrease [Ca(2+)](i) in the RPMC through the NO-cGMP pathway. This procession is related with the L- type voltage-gated Ca(2+) channel. NO enlarges the opening area of the lymphatic stomata and enhances the lymph drainage of tracer by NO-cGMP-[Ca(2+)](i) pathway.
Animals ; Calcium Signaling ; physiology ; Cyclic GMP ; metabolism ; Female ; Lymph ; physiology ; Lymphatic Vessels ; physiology ; Male ; Nitric Oxide ; physiology ; Peritoneal Stomata ; physiology ; Random Allocation ; Rats ; Rats, Sprague-Dawley