Ischemia cyclic nucleotides

Disorders that cause increased secretion of fluid and electrolytes into the small intestine of the horse are characterized by abdominal discomfort, distension of the small intestine and enterogastric reflux. In young foals with small intestinal secretory disorders, diarrhea may occur. Increased intestinal secretion can result from the active secretion of electrolytes and water, for example the cyclic nucleotide-stimulated secretion that results from exposure to bacterial enterotoxins. Passive secretion of water can result from increased permeability of the intestine, such as in enteritis, distension or ischemia, or decreased absorption of osmoti-caUy active substances, such as with lactose intolerance in foals. Disorders in which there is decreased secretion of fluid into the small intestine are not appreciated, although impactions of ingesta in segments of the small intestine can occur. 

PKG and cyclic nucleotide phosphodiesterases (PDEs) (reviewed by Baxter37). A rapid release of natriuretic peptides and induction of their de novo synthesis occurs in myocardial ischemia. Natriuretic peptides may have a cardioprotective role. BNP-32 administration in perfused rat hearts prior to left main coronary artery occlusion and until 30 min of reperfusion resulted in limitation of infarct size in a concentration dependent manner. Furthermore, this effect was abolished by 5-hydroxydecanoate (presumed to be a selective blocker of mitochondrial KATp channels), L-NAME, an inhibitor of NOS and ODQ, a specific soluble guanyl cyclase inhibitor.38 Similarly, human recombinant ANP limited infarct size and reperfusion arrhythmias in a canine model of coronary occlusion and reperfusion.39... 

E. F. Du Toit, C. A. Muller, J. McCarthy, L. H. Opie, Levosimendan effects of a calcium sensitizer on function and arrhythmias and cyclic nucleotide levels during ischemia/reperfusion in the Langcndorff-perfused guinea pig heart, J Pharmacol Exp Ther 290, 505-14 (1999). 

Fig. 4.6 Time course of cyclic nucleotides in global ischemia. The left ordinate indicate the concentrations of cyclic AMP and on the right are those for the cyclic GMP. The concentrations of cyclic AMP and cyclic GMP are expressed in pmol/mg protein and fmol/mg protein, respectively, indicating the order of magnitude lower amounts of cyclic GMP...

Kobayashi, M., Lust, W.D., and Passonneau, J.V. (1977) Concentrations of energy metabolites and cyclic nucleotides during and after bilateral ischemia in the gerbil cerebral cortex. J. Neurochem., 29 53-59. 

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