Objective:Albeit the effects of hypercholesterolemia on ion channels' and smooth muscle cells' functions have been investigated extensively, limited information on function of urinary bladder is available. Therefore, we aimed to investigate the effects of hypercholesterolemia on contractions of in vitro urinary bladder smooth muscles in rats.

Methods: 

Serum lipid profiles and tissue cholesterol levels of adult male Sprague-Dawley rats, fed with standard (C, n=25) or 4% cholesterol diet (HC, n=26) for four weeks were measured. Aorta was examined microscopically for atherosclerosis. Spontaneous contractions of detrusor muscle strips and their responses to 80mM KCl and electrical field stimulation (EFS) or cumulative dose-contraction curves to carbachol (10-8-10-4M) were recorded. Carbachol dose-contraction curves were repeated in the presence of L-type calcium channel blocker nifedipine (10–6M) and/or rho-kinase inhibitor Y27632 (10–5M). Data were analyzed statistically.

Results: 

Plasma cholesterol was elevated in HC group (C:89.24±3.81, HC:155.38±9.66 mg/dL, P<0.05), tissue cholesterol levels were similar. There was no sign of atherosclerosis. The amplitude of basal spontaneous (P>0.05) and KCl-induced (P<0.05) contractions were greater in HC group (HC:29.1±1.7; C:21.2±1.6 g/100mg tissue). EFS and carbachol-induced contractions were comparable among groups. Nifedipine, Y27632 and nifedipin+Y27632 reduced carbachol-induced contractions to 39%, 23%, 88% of pre-drug controls in the C group and to 68%, 22%, 90% of pre-drug controls in the HC group.

Conclusions: 

Increased KCl-induced and spontaneous contractions together with potent attenuation of carbachol-induced contractions with nifedipine strips in hypercholesterolemia group, collectively, suggest that hypercholesterolemia has an impact on both sarcolemmal L-type calcium channels and contractions of detrusor strips.