ABSTRACT
PURPOSE: The aim of this study was to evaluate the relaxation in vitro of cavernous smooth muscle induced by a new NO donor of the complex nitrosil-ruthenium, named trans-[Ru(NH3)4(caffeine)(NO)]C13 (Rut-Caf) and sodium nitroprusside (SNP). MATERIALS AND METHODS: The tissues, immersed in isolated bath systems, were pre-contracted with phenilephrine (PE) (1 µM) and then concentration-response curves (10-12 - 10-4 M) were obtained. To clarify the mechanism of action involved, it was added to the baths ODQ (10 µM, 30 µM), oxyhemoglobin (10 µM), L-cysteine (100 µM), hydroxicobalamine (100 µM), glibenclamide, iberotoxin and apamine. Tissue samples were frozen in liquid nitrogen to measure the amount of cGMP and cAMP produced. RESULTS: The substances provoked significant relaxation of the cavernous smooth muscle. Both Rut-Caf and SNP determined dose-dependent relaxation with similar potency (pEC50) and maximum effect (Emax). The substances showed activity through activation of the soluble guanylyl cyclase (sGC), because the relaxations were inhibited by ODQ. Oxyhemoglobin significantly diminished the relaxation effect of the substances. L-cysteine failed to modify the relaxations caused by the agents. Hydroxicobalamine significantly diminished the relaxation effect of Rut-Caf. Glibenclamide significantly increased the efficacy of Rut-Caf (pEC50 4.09 x 7.09). There were no alterations of potency or maximum effect of the substances with the addition of the other ion channel blockers. Rut-Caf induced production of significant amounts of cGMP and cAMP during the relaxation process. CONCLUSIONS: In conclusion, Rut-Caf causes relaxation of smooth muscle of corpus cavernosum by means of activation of sGC with intracellular production of cGMP and cAMP; and also by release of NO in the intracellular environment. Rut-Caf releases the NO free radical and it does not act directly on the potassium ion channels.
Subject(s)
Animals , Male , Rabbits , Muscle Relaxation/physiology , Muscle, Smooth/drug effects , Nitric Oxide Donors/pharmacology , Nitroprusside/pharmacology , Ruthenium Compounds/pharmacology , Cyclic GMP/biosynthesis , Cyclic GMP/chemistry , Cysteine/pharmacology , Guanosine Monophosphate/biosynthesis , Guanosine Monophosphate/chemistry , Muscle, Smooth/physiology , Nitric Oxide Donors/chemistry , Nitroprusside/chemistry , Potassium Channels/chemistry , Ruthenium Compounds/chemistry , Time FactorsABSTRACT
The study was conducted to determine the effects of boiled extract of Cleistanthus collinus on rats by observing ECG changes and electrolyte levels in serum and urine. Influence of minoxidil and glibenclamide on Cleistanthus collinus induced toxicity was determined. ED50 for arrhythmia, changes in contractility and heart rate were recorded using the isolated frog heart. Cleistanthus at low doses caused transient tachycardia and increase in contractility and at high dose caused arrhythmia and cardiac arrest in rat. LD50 was found to be 1690 mg/kg. Minoxidil potentiated cardiac toxicity, whereas glibenclamide did not produce any significant change. High concentration of potassium in Cleistanthus extract hindered comparison of its levels. There was excretion of sodium even in the presence of hyponatraemia. Cleistanthus at low dose caused transient tachycardia and increase in contractility and at high dose caused arrhythmia and cardiac arrest in isolated frog heart. ED50 for arrhythmia was found to be 1406 mg/kg. Acute toxicity was mainly due to depressive cardiac activity of Cleistanthus. It also caused renal failure. Potassium channel modulators did not have important role in acute cardiac toxicity treatment. Probably in chronic toxicity, electrolyte level changes are involved and potassium channel modulators might have a role.
Subject(s)
Animals , Electrocardiography , Electrolytes/metabolism , Female , Glyburide/pharmacology , Glycosides/toxicity , Heart/drug effects , Hydrogen-Ion Concentration , Lignans/toxicity , Male , Minoxidil/pharmacology , Myocardium/metabolism , Plant Extracts , Potassium/chemistry , Potassium Channels/chemistry , Ranidae , Rats , Rats, Wistar , Sodium/chemistry , Time Factors , TreesABSTRACT
Bartter-like syndrome encompasses a set of inherited renal tubular disorders associated with hypokalemic metabolic alkalosis, renal salt wasting, hyperreninemic hyperaldosteronism, and normal blood pressure. Antenatal Bartter syndrome, a subtype of Bartter-like syndrome, is characterized by polyhydramnios, premature delivery, life-threatening episodes of fever and dehydration during the early weeks of life, growth retardation, hypercalciuria, and early-onset nephrocalcinosis. Mutations in the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) and ATP-sensitive inwardly rectifying potassium channel (ROMK) of the thick ascending limb of Henle's loop have been identified in the antenatal Bartter syndrome. We report the identification of two heterozygous mutations of the gene for Kir 1.1 (ROMK) from an antenatal Bartter syndrome patient who presented at birth with mild salt wasting and a biochemical findings that mimicked primary peudohypoaldosteronism type 1, such as hyperkalemia and hyponatremia, and evolved to a relatively benign course. We have identified amino acid exchanges Arg338Stop and Met357Thr in the gene exon 5 for ROMK by PCR and direct sequencing. Both mutations alter the C-terminus of the ROMK protein, and can affect channel function.