Effect of human chorionic gonadotrophin on in vitro contractions of stimulated detrusor muscle strips of female rats

Aims: We studied the effect of human chorionic gonadotrophin (hCG) on the in vitro detrusor muscle contractions in female rats. Methods: Two adjacent detrusor muscle strips from the bladder dome of 18 female Wistar rats (230-250 gm) were mounted in an organ bath for the recording of isometric tension. Carbachol (10^-9-10^-3 M), α,β methylene adenosine 5′-triphosphate (ATP) (10^-9-10^-3 M) and potassium chloride (KCl) (10^-4-10^-3 M) were applied (n = 6 × 3 groups). Concentration-response curves, before and after the addition of hCG (100 iu/mL) or oxybutynin (10^-5 M) to either muscle strip, were compared. Results: All curves were displaced to the right by hCG in a concentration-dependent manner with significant inhibition of contractions induced by carbachol (P < 0.001) and KCl (P = 0.016) but not those induced by α,β-methylene ATP (P = 0.4). Estimated order of potency of inhibition was carbachol>KCl>α,β-methylene ATP. The overall inhibitory effect of hCG was significantly less than oxybutynin (P < 0.001). Conclusions: hCG significantly inhibited in vitro detrusor contractions induced by depolarization (KCl) and cholinergic (carbachol) but not purinergic (α,β-methylene ATP) stimulation in a dose-dependent manner in female rats.