Inhibitory effect of nicorandil on the contraction of isolated human urinary bladder detrusor muscle.

This study was performed to determine whether the antianginal drug nicorandil relaxes isolated human detrusor muscle. Ten strips of detrusor muscle obtained from 10 pediatric patients who underwent surgery on the urinary bladder were contracted with 80 mM potassium chloride (KCl) before and after incubation with four concentrations of nicorandil (100, 200, 400 and 800 microM). The percent inhibition by nicorandil of the height and area under the curve (AUC) of KCl-induced contractions of the detrusor strips was calculated. The effect of glibenclamide (10 microM) on nicorandil (800 microM)-induced inhibition of KCl-induced detrusor contractions was also studied. Nicorandil caused a concentration-dependent inhibition of KCl-induced contractions of the detrusor strips. The percent inhibition of the height of KCl-induced contractions of the detrusor by nicorandil was significant at concentrations of 200, 400 and 800 microM. The percent inhibition of the AUC for KCl-induced detrusor contractions was significant at all four concentrations of nicorandil used. Glibenclamide reversed the inhibitory effect of 800 microM nicorandil on KCl-induced detrusor contractions. These results suggest that nicorandil inhibits KCl-induced contractions of isolated human detrusor muscle and may therefore be useful in clinical conditions requiring detrusor muscle relaxation.

Inhibition of Spontaneous Contractility of Isolated Caprine Ureter by Flupirtine.

CONTEXT: Kv7 potassium channels are expressed in several types of smooth muscles and could mediate physiological responses in the tissues expressed. Flupirtine is an analgesic that acts by opening Kv7 potassium channels. It has been shown to inhibit the contractility of several types of isolated smooth muscle. AIMS: This study investigated the ability of flupirtine to inhibit the spontaneous contractility of isolated distal caprine (goat) ureter. SETTINGS AND DESIGN: Spontaneous contractility of the isolated goat ureter was recorded using a physiograph. MATERIALS AND METHODS: The ability of 1, 3, 10, 30, and 90 µM concentrations of flupirtine maleate to inhibit the spontaneous contractility of isolated distal goat ureter was investigated. The ability of the nonspecific potassium channel blocker 4-aminopyridine (4-AP; 1 mM) and the specific Kv7 channel blocker XE-991 (100 µM) to reverse the inhibitory effect of flupirtine on ureteric contractility was also investigated. STATISTICAL ANALYSIS USED: Both parametric and nonparametric statistical tests were used. RESULTS: At 10, 30, and 90 µM concentrations, flupirtine significantly inhibited the spontaneous contractility of the isolated goat ureter. The EC50 of flupirtine for a contact period of 10 min was 17.7 µM. The inhibitory effect of flupirtine on ureteric contractility was significantly reversed by 4-AP and XE-991. CONCLUSIONS: Flupirtine inhibits the spontaneous contractility of the isolated goat ureter by opening Kv7 channels.

The effect of a nicorandil congener on isolated human myometrium.

OBJECTIVE: To determine the effect of a nicorandil congener, SG-209 on the myometrium. STUDY DESIGN: Isolated strips of myometrium, from nine women who underwent hysterectomy, were made to contract with 55 mM KCl before and after incubation with three concentrations of SG-209 (1.5, 3.0 and 10 microM). The mean height of contraction and the area under the curve were analysed using a non-parametric test. RESULTS: At a 10 microM concentration, SG-209 significantly decreased the mean area under the curve from 10.8 to 2.5 cm2 (p<0.05). CONCLUSION: SG-209 significantly relaxes the human non-pregnant myometrium. Along with its congener, nicorandil, it may be useful in clinical conditions that require uterine relaxation.

Inhibitory effect of curcumin on the contractility of isolated caprine detrusor muscle.

Curcumin is a naturally occurring compound which has been used in traditional medicine in India for a long time. This study investigated the ability of curcumin to inhibit the contractility of isolated caprine (goat) detrusor muscle. The ability of three concentrations of curcumin (30, 100 and 300 µM) to inhibit the 100 µM acetylcholine-induced contractility of the isolated caprine urinary bladder detrusor muscle was investigated. The effect of raising the concentration of acetylcholine from 100, 200 and 400 µM to overcome the curcumin-induced inhibition of detrusor contractility and the effects of the reversal agents tetraethylammonium, a potassium channel blocker (100 µM), glibenclamide, an ATP-sensitive potassium channel blocker (10 µM), and propranolol, a beta adrenergic receptor blocker (1 µM), on the inhibitory effect of detrusor contractility was also studied. Curcumin caused a concentration-dependent inhibition of acetylcholine-induced contractility of the isolated detrusor muscle which was statistically significant at all three concentrations of curcumin used. This inhibition was partially overcome by raising the concentration of ACh to 200 and 400 µM. The inhibition was overcome by the concurrent administration of tetraethylammonium. Glibenclamide reversed the inhibitory effect of 100 µM curcumin, but not that of 300 µM curcumin. Propranolol reversed the inhibitory effect of 100 µM curcumin but not that of 300 µM curcumin. These results suggest that curcumin inhibited the contractions of the isolated detrusor muscle. The results further suggest that the inhibitory effect is mediated by various mechanisms: stimulation of beta adrenergic receptors; an anticholinergic effect; and the opening of ATP-sensitive potassium channels.

Effect of potassium channel modulators on toxicity of Cleistanthus collinus.

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.

Comparison of intralesional verapamil with intralesional triamcinolone in the treatment of hypertrophic scars and keloids.

BACKGROUND: The calcium channel blocker, verapamil stimulates procollagenase synthesis in keloids and hypertrophic scars. AIM: To study the effect of verapamil in the treatment of hypertrophic scars and keloids and to evaluate the effect of verapamil on the rate of reduction of hypertrophic scars and keloids in comparison with triamcinolone. METHODS: The study was a randomized, single blind, parallel group study in which 54 patients were allocated to to receive either verapamil or triamcinolone. Drugs were administered intralesionally in both groups. Improvement of the scar was measured using modified Vancouver scale and by using a centimeter scale serially till the scar flattened. RESULTS: There was a reduction in vascularity, pliability, height and width of the scar with both the drugs after 3 weeks of treatment. These changes were present at one year of follow-up after stopping treatment. Scar pigmentation was not changed desirably by either drug. Length of the scars was also not altered significantly by either drug. The rate of reduction in vascularity, pliability, height and width of the scar with triamcinolone was faster than with verapamil. Adverse drug reactions were more with triamcinolone than with verapamil. CONCLUSION: Intralesional verapamil may be a suitable alternative to triamcinolone in the treatment of hypertrophic scars and keloids.