[Effects of chronic low-frequency electrical stimulation on the external urethral sphincter of male rabbits--electrophoretic analyses of myosin light and heavy chain isoforms].

The present study investigates the effects of chronic low-frequency electrical stimulation on the external urethral sphincter (EUS) of rabbits through the biochemical analysis of the isoforms of myosin light and heavy chains. Twenty-eight adult male rabbits were used in the test. Of these, the EUS of 14 rabbits were continuously stimulated directly at 1.8 Hz, 0.8 msec, 5.0 V with an implantable electrical cardiac pacemaker for more than 10 weeks. The other 14 rabbits were used as the control group and were nurtured under the same conditions as the stimulated group but without the electrical stimulation. Upon conclusion of the stimulation program, the urethra was removed from all 28 rabbits. The portion of the urethra containing the EUS (from the middle of the prostate to the pelvic diaphragm) was cut transversely into thin serial sections and glycerinated. The glycerinated muscle fibers were then isolated under a stereomicroscope and samples for electrophoretic analysis were prepared. Two-dimensional electrophoresis according to the procedure of O'Farrell for myosin light chains and SDS-PAGE containing 40% glycerol for myosin heavy chains were carried out. The molar ratio of myosin subunits was determined by quantification through the dye elution process. The average percentages of slow myosin light chain molecules in 8 unstimulated and 8 stimulated EUS were 33.4 +/- 8.9% (mean +/- SD) and 70.1 +/- 12.8%, respectively. The average percentages of slow myosin heavy chain molecules in 6 unstimulated and 6 stimulated EUS were 17.6 +/- 5.7% and 40.2 +/- 7.1%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)