Bladder smooth muscle cell phenotypic changes and implication of expression of contractile proteins (especially caldesmon) in rats after partial outlet obstruction.
BACKGROUND
The purpose of the present study was to investigate morphological changes in bladder smooth muscle of rats with partial outlet obstruction. We investigated smooth muscle cell phenotypic changes and implication of synthetic phenotype in contractility decrease and bladder compliance after bladder outlet obstruction.


METHODS
Partial bladder outlet obstruction was introduced in female rats. Bladder were removed at 1, 3, 6, 10 and 20 weeks after the obstruction. Temporal pattern of changes in bladder mass, light microscopic pathogenesis and phenotypic expression of the bladder smooth muscle cells in the electron micrographs were investigated. Expression of contractile protein was also investigated by the immunoblotting method.


RESULTS
Marked increase in bladder mass with marked thickening of smooth muscle layer was observed at 1 week after obstruction. The ratio of myocytes exhibiting contractile and synthetic phenotypes was almost constant until 6 weeks after the obstruction, but thereafter, synthetic phenotypes gradually increased and the ratio (synthetic/contractile phenotype) was 1.5-fold at 20 weeks after the obstruction. Caldesmon was most markedly expressed after the obstruction among contractile proteins examined by the immunoblotting method.


CONCLUSIONS
Phenotypic changes were confirmed in bladder smooth muscle, and the decrease of the ratio of contractile phenotype was observed after long-term obstruction of the bladder outlet. Among the contractile proteins in the bladder smooth muscle cell, caldesmon was considered a reliable marker for predicting the pathogenetic conditions of the bladder.
Matsumoto
Seiji
S
Department of Urology, Kinki University, Osaka, Japan. urology@med.kindai.ac.jp
Hanai
Tadashi
T
Ohnishi
Norio
N
Yamamoto
Kazuhiko
K
Kurita
Takashi
T
D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D003285:Contractile Proteins / Q000378:metabolism*; D005260:Female; D009130:Muscle, Smooth / Q000378:metabolism / Q000503:physiopathology*; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D001743:Urinary Bladder / Q000378:metabolism / Q000503:physiopathology*; D001748:Urinary Bladder Neck Obstruction / Q000235:genetics* / Q000378:metabolism*
D002148:Calmodulin-Binding Proteins; D003285:Contractile Proteins