Effect of calcium and calcium chelator on the response of the bladder to in vitro ischaemia

Abstract

Objective To examine the eCect of diCerent concensolution, resulted in a diminished response to all stimuli. This contractile dysfunction was least in the trations of calcium on the contractile responses of isolated strips of rabbit bladder detrusor to various presence of calcium chelator (EGTA) and greatest in the presence of 5.4 mmol/L calcium. Repetitive stimuforms of stimulation after 2 h incubation in the presence of substrate and oxygen depletion (in vitro ischaelation during in vitro ischaemia also exacerbated the contractile dysfunction. Lipid peroxidation increased mia), followed by 1 h of recovery. The resultant contractile responses were correlated with the level of during in vitro ischaemia in proportion to the calcium concentration and was enhanced by repetitive stimulalipid peroxidation as determined by malonedialdehyde (MDA) concentration.tion during this period. Regardless of the incubation conditions, the reduction in the contractile response Materials and methods Isolated strips of rabbit bladder detrusor smooth muscle were incubated in Tyrode's was significantly greater for field-stimulated tissues than for those stimulated with carbachol or KCl. solution containing diCerent concentrations of calcium (0-5.4 mmol/L). The eCect of 2 h of incubation inConclusions These results show that the magnitude of contractile dysfunction induced by incubation in the oxygen-and substrate-free medium (in vitro ischaemia), followed by a 1-h incubation in the presence of presence of substrate and oxygen depletion is reduced in the presence of low calcium concentrations, oxygen and substrate, on the contractile responses to field stimulation, carbachol and KCl were determined.increased in the presence of high calcium levels and increased in the presence of repetitive stimulation. In The eCects of repetitive stimulation (15 s of stimulation at 32 Hz applied every 5 min during the 2-h experaddition, the level of lipid peroxidation after the recovery period was proportional to the magnitude of imental period) were also assessed. Results The contractile responses to all stimuli increased contractile dysfunction present.

Effect of Age on the Response to in vitro Ischemia and Reperfusion of the Rabbit Bladder

“…This is consistent with previous studies showing that neuronal membranes (responsible for neurotransmitter release by FS) are significantly more sensitive to hypoxic and I/R damage than muscarinic receptors (which are stimulated by carbachol) or smooth muscle cell membranes (which are depolarized by KCl) [5,6,12,[13][14][15] .…”

“…Studies using an in vitro model of I/R have clearly demonstrated that this model produces contractile and metabolic damage similar to that of partial outlet obstruction [5,6] . The metabolic damage is mediated by the oxidation of proteins and lipids within the various cellular and subcellular membrane systems and can be quan-titated by analyzing the affected tissue for the oxidative metabolite malondialdehyde (MDA) [5,6] .…”

“…The metabolic damage is mediated by the oxidation of proteins and lipids within the various cellular and subcellular membrane systems and can be quan-titated by analyzing the affected tissue for the oxidative metabolite malondialdehyde (MDA) [5,6] . In addition, repetitive stimulation (a model of unstable bladder contractions) resulted in a greater rate of contractile failure and metabolic damage (increased production of MDA) under all conditions tested [6] .…”

The use of Hypochlorous Acid as a Model for Investigating Bladder Overactivity

“…Possibly, the detrusor dysfunction is caused by activation of specific hydrolytic enzymes including calpain and phospholipase A 2 with subsequent damage to intracellular organelles such as the mitochondria and sarcoplasmic reticulum and via generation of reactive oxygen species and subsequent membrane lipid peroxidation (12,13).…”

Influence of oxidative stress on inducing micturition dysfunction following chronic infravesical obstruction and the protective role of an antioxidant diet - association of in vivo and in vitro studies in rats

“…Levin et al demonstrated that, when muscle tissue was exposed to free radical generation, there was an accumulation of calcium in the intracellular medium, which would be responsible for cell damage. Thus, they suggested that galangin would act through type L calcium channels, thereby avoiding increased transportation of calcium ions into cells (17). There would, of course, be a need for studies to elucidate the exact mechanism for the action of galangin, in order to characterize the diseases for which galangin could become part of the therapeutic arsenal.…”