AIM: To systematically investigate if cGMP/cGMP- dependent protein kinase G (PKG) signaling pathway may participate in dendroaspis natriuretic peptide (DNP)-induced relaxation of gastric circular smooth muscle. METHOD...AIM: To systematically investigate if cGMP/cGMP- dependent protein kinase G (PKG) signaling pathway may participate in dendroaspis natriuretic peptide (DNP)-induced relaxation of gastric circular smooth muscle. METHODS: The content of cGMP in guinea pig gastric antral smooth muscle tissue and perfusion solution were measured using radioimmunoassay; spontaneous contraction of gastric antral circular muscles recorded using a 4-channel physiograph; and Ca2+-activated K+ currents (IK(Ca)) and spontaneous transient outward currents (STOCs) in isolated gastric antral myocytes were recorded using the whole-cell patch clamp technique. RESULTS: DNP markedly enhanced cGMP levels in gastric antral smooth muscle tissue and in the perfusion medium. DNP induced relaxation in gastricantral circular smooth muscle, which was inhibited by KT5823, a cGMP-dependent PKG inhibitor. DNP increased IK(Ca). This effect was almost completely blocked by KT5823, and partially blocked by LY83583, an inhibitor of guanylate cyclase to change the production of cGMP. DNP also increased STOCs. The effect of DNP on STOCs was abolished in the presence of KT5823, but not affected by KT-5720, a PKA-specific inhibitor. CONCLUSION: DNP activates IK(Ca) and relaxes guinea-pig gastric antral circular smooth muscle via the cGMP/PKG-dependent singling axis instead of cAMP/ PKA pathway.展开更多
This study was carried out to clarify role of ceca in nitrogen nutrition of the chicken. Exp. 1： The effect of cecal ligation on nitrogen utilization and excretion was investigated in chickens fed 5% to 14% protein d...This study was carried out to clarify role of ceca in nitrogen nutrition of the chicken. Exp. 1： The effect of cecal ligation on nitrogen utilization and excretion was investigated in chickens fed 5% to 14% protein diet. Irrespective of dietary protein level and different protein sources, the ligation of cecal decreased uric acid excretion and tended to increase nitrogen utilization and balance with the exception of urea-added 10% protein diet. Exp. 2： The effect of cecal ligation on nitrogen utilization and excretion was investigated in conventional and colostomized chickens fed a 5% protein diet or 5% protein diet plus urea. Total nitrogen excretion and uric acid excretion increased by colostomy were depressed by cecal ligation in chickens. Therefore, nitrogen utilization and balance decreased by colostomy were increased by cecal ligation. Urinary nitrogen excretion was significantly decreased by cecal ligation in colostomized chickens, but the cecal ligation did not change fecal nitrogen excretion in chickens fed either diet. Exp. 3： This experiment was carried out to examine the effects of removal of cecal contents on nitrogen utilization, balance and nitrogen excretion in cecally ligated chickens. Total nitrogen excretion was significantly decreased by washing out the cecal contents with saline or antibiotics. The cecal ligation and the removal of cecal contents significantly decreased uric acid excretion in the excreta. There was a highly inverse relationship between microbial counts in the ceca and an excretory amount of uric acid. Exp. 4： In order to examine effects of cecal ligation on microbial activity, microbes were counted and products of microbial fermentation were determined. The ligation of caeca decreased microbial counts, concentrations of acetic, propionic and butyric acids and ammonia concentration of cecal contents. These results suggest that nitrogen metabolism in chickens is affected by possible changes in cecal fermentation caused by preventing the substances from urine and digesta from entering into the ceca.展开更多
基金The National Natural Science Foundation of China, No. 30800382the Youth Science Foundation of Dalian to Professor Hui-Shu Guo, No. 2006B3NS218
文摘AIM: To systematically investigate if cGMP/cGMP- dependent protein kinase G (PKG) signaling pathway may participate in dendroaspis natriuretic peptide (DNP)-induced relaxation of gastric circular smooth muscle. METHODS: The content of cGMP in guinea pig gastric antral smooth muscle tissue and perfusion solution were measured using radioimmunoassay; spontaneous contraction of gastric antral circular muscles recorded using a 4-channel physiograph; and Ca2+-activated K+ currents (IK(Ca)) and spontaneous transient outward currents (STOCs) in isolated gastric antral myocytes were recorded using the whole-cell patch clamp technique. RESULTS: DNP markedly enhanced cGMP levels in gastric antral smooth muscle tissue and in the perfusion medium. DNP induced relaxation in gastricantral circular smooth muscle, which was inhibited by KT5823, a cGMP-dependent PKG inhibitor. DNP increased IK(Ca). This effect was almost completely blocked by KT5823, and partially blocked by LY83583, an inhibitor of guanylate cyclase to change the production of cGMP. DNP also increased STOCs. The effect of DNP on STOCs was abolished in the presence of KT5823, but not affected by KT-5720, a PKA-specific inhibitor. CONCLUSION: DNP activates IK(Ca) and relaxes guinea-pig gastric antral circular smooth muscle via the cGMP/PKG-dependent singling axis instead of cAMP/ PKA pathway.
文摘This study was carried out to clarify role of ceca in nitrogen nutrition of the chicken. Exp. 1： The effect of cecal ligation on nitrogen utilization and excretion was investigated in chickens fed 5% to 14% protein diet. Irrespective of dietary protein level and different protein sources, the ligation of cecal decreased uric acid excretion and tended to increase nitrogen utilization and balance with the exception of urea-added 10% protein diet. Exp. 2： The effect of cecal ligation on nitrogen utilization and excretion was investigated in conventional and colostomized chickens fed a 5% protein diet or 5% protein diet plus urea. Total nitrogen excretion and uric acid excretion increased by colostomy were depressed by cecal ligation in chickens. Therefore, nitrogen utilization and balance decreased by colostomy were increased by cecal ligation. Urinary nitrogen excretion was significantly decreased by cecal ligation in colostomized chickens, but the cecal ligation did not change fecal nitrogen excretion in chickens fed either diet. Exp. 3： This experiment was carried out to examine the effects of removal of cecal contents on nitrogen utilization, balance and nitrogen excretion in cecally ligated chickens. Total nitrogen excretion was significantly decreased by washing out the cecal contents with saline or antibiotics. The cecal ligation and the removal of cecal contents significantly decreased uric acid excretion in the excreta. There was a highly inverse relationship between microbial counts in the ceca and an excretory amount of uric acid. Exp. 4： In order to examine effects of cecal ligation on microbial activity, microbes were counted and products of microbial fermentation were determined. The ligation of caeca decreased microbial counts, concentrations of acetic, propionic and butyric acids and ammonia concentration of cecal contents. These results suggest that nitrogen metabolism in chickens is affected by possible changes in cecal fermentation caused by preventing the substances from urine and digesta from entering into the ceca.
