Effect of partial outlet obstruction on rabbit urinary bladder smooth muscle function.
Bladder outlet obstruction secondary to benign prostate hyperplasia is associated with many cellular changes. This study was designed to determine whether these changes involve the contractile apparatus. Bladder smooth muscles from rabbits subjected to partial outlet obstruction for 2 wk were mounted for isometric force, isotonic shortening velocity, and myosin light chain (MLC) phosphorylation levels. Muscle strips from obstructed bladders exhibited spontaneous phasic activity; muscle strips from control bladders did not. Muscle strips from obstructed bladders exhibited increased sensitivity and higher levels of stress in response to the cumulative addition of KCl or carbachol compared with control. During noncumulative addition of KCl or carbachol, no differences in sensitivity were noted. Muscle strips from obstructed bladders had elevated basal MLC phosphorylation levels and stimulation produced small increases in MLC phosphorylation compared with control. V(max) during KCl stimulation of muscle strips from obstructed bladders was 10-fold lower than control. Our results suggest that bladder outlet obstruction produces a muscle cell that develops higher levels of force but with greatly reduced cross bridge cycling rates.
Su
Xiaoling
X
Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia 19102, USA.
Stein
Raymund
R
Stanton
Michaela C
MC
Zderic
Stephen
S
Moreland
Robert S
RS
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D004195:Disease Models, Animal; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D007551:Isotonic Contraction / Q000187:drug effects; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D001743:Urinary Bladder / Q000473:pathology / Q000503:physiopathology*; D001748:Urinary Bladder Neck Obstruction / Q000503:physiopathology*
D018679:Cholinergic Agonists; D018994:Myosin Light Chains; D011189:Potassium Chloride; D002217:Carbachol