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Myosin isoforms in female human detrusor
M P FitzGerald1, V Manaves, A F Martin
1Department of Obstetrics and Gynecology, Section of Urogynecology and Pelvic Reconstructive Surgery, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois, USA. mfitzg8@luc.edu
Neurourology and Urodynamics
|January 3, 2001
Summary
Detrusor smooth muscle in women has a consistent myosin isoform ratio (34% SM1, 66% SM2). This ratio remains unchanged in women with detrusor overactivity, suggesting animal models may not accurately reflect human bladder conditions.
Area of Science:
- Urology
- Molecular Biology
- Muscle Physiology
Background:
- Detrusor overactivity is a condition affecting bladder function.
- Myosin heavy chain (MHC) isoforms play a role in smooth muscle contractility.
- Understanding MHC isoform distribution in the detrusor muscle is crucial for bladder research.
Purpose of the Study:
- To determine the relative proportions of SM1 and SM2 myosin heavy chain isoforms in the detrusor smooth muscle of women.
- To compare isoform distribution between women with detrusor overactivity and asymptomatic controls.
- To assess the influence of race and urogynecologic diagnosis on detrusor myosin isoform composition.
Main Methods:
- Full-thickness bladder dome biopsies were obtained from women undergoing laparotomy.
- Myosin heavy chain isoforms were separated and quantified using polyacrylamide gel electrophoresis and densitometry.
- Protein extracts were analyzed from six patients with detrusor overactivity and eight continent controls.
Main Results:
- Detrusor smooth muscle predominantly contains SM2 (66%) and SM1 (34%) myosin heavy chain isoforms.
- No significant differences in SM1/SM2 isoform ratios were observed between women with detrusor overactivity and controls.
- Isoform distribution was consistent across different races and did not vary with urogynecologic diagnosis.
Conclusions:
- The myosin heavy chain isoform ratio in female detrusor smooth muscle is relatively constant (approximately 34% SM1, 66% SM2).
- Detrusor overactivity in women does not appear to alter this myosin isoform composition.
- Current animal models of bladder outlet obstruction may not be suitable for studying human detrusor instability due to differing myosin isoform responses.