Myosin isoforms in female human detrusor

The aim of this study was to document the relative proportions of two isofo rms of myosin heavy chain in detrusor smooth muscle of women with detrusor overactivity and in asymptomatic controls. Women aged 35-65 with documented detrusor overactivity and without a history of neurologic disease, prior i ncontinence surgery, elevated post-void residual urine volume, or indwellin g urinary catheter were eligible fur the study. Full-thickness biopsies of extraperitoneal bladder dome were obtained at the time of laparotomy in six patients with documented detrusor overactivity and in a control group of e ight continent patients. Biopsies were frozen in liquid nitrogen, crushed w ith a frozen mortar and pestle at -80 degreesC, and homogenized in buffer, and the extracts were electrophoresed on 6% polyacrylamide sodium dodecyl s ulfate gels and stained with Coomassie blue. The gels were de-stained and t hen the protein bands were scanned with a densitometer. The mean patient ag e was 48 years (range, 36-59). Seven patients were Caucasian and seven pati ents were African American. Detrusor smooth muscle contains a mean of 34% ( range, 27-43%) SM1 and 66% (range, 57-73%) SM2 isoforms. There was no diffe rence in isoform composition when patients were compared according to urogy necologic diagnosis or according to race. In detrusor biopsies from women, approximately 34% of myosin is of the SMI isoform and approximately 66% is of the SM2 isoform. This ratio is relatively constant in the two races stud ied and unchanged in women with detrusor overactivity. Animal models utiliz ing outlet obstruction of the bladder to provoke detrusor instability and d etrusor hypertrophy are known to alter myosin isoform distribution and may not be appropriate models of detrusor instability in human females. Neurour ol. Urodynam. 20:23-29, 2001. (C) Wiley-Liss, Inc.