Effects of ovariectomy and oestrogen replacement on the function and expression of Rho-kinase in rat bladder smooth muscle.
OBJECTIVE
To investigate the effects of ovariectomy and oestrogen replacement on the function and expression of Rho-kinase in rat bladder smooth muscle, as the actual effects of oestrogen deprivation on bladder smooth muscle are unclear.


METHODS
Female Sprague-Dawley rats were placed into one of three groups: sham-operated, bilateral ovariectomy-only, and bilateral ovariectomy plus oestrogen replacement groups. In the last group, oestrogen was replaced by weekly injection of beta-estradiol 17-cypionate (250 microg/kg subcutaneously for 6 weeks) beginning at 1 week after ovariectomy, whereas the other groups received vehicle-only injections for 6 weeks. After treatment, the bladder was removed for muscle strip studies to evaluate the effects of Y-27632, a specific inhibitor of Rho-kinase, on baseline tension and carbachol-induced tonic contractions. Also, the protein expression of RhoA and Rho-kinase isoenzymes was assessed by Western blot analysis.


RESULTS
Of the three groups, incubation with 10 microm Y-27632 resulted in the largest decrease in baseline tension of strips from the bilateral ovariectomy-only group, but this was not statistically significant (P > 0.05). For carbachol-induced tonic contractions, strips from the bilateral ovariectomy-only group were attenuated the most among the three groups after adding Y-27632 (P < 0.05). However, there were no significant differences in the levels of RhoA and the two Rho-kinase isoenzymes in bladder tissues from the three groups.


CONCLUSIONS
Our data show that oestrogen might inhibit the function of Rho-kinase in bladder smooth muscle, while having no significant effect on its expression. This finding might help to explain the greater incidence of urinary tract symptoms suggestive of overactive bladder after the menopause in women.
Hong
Sung K
SK
Department of Urology, Seoul National University, Seoul, Korea.
Yang
Ji H
JH
Kim
Tae B
TB
Kim
Soo W
SW
Paick
Jae-Seung
JS
D000818:Animals; D015153:Blotting, Western; D015914:Estrogen Replacement Therapy; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology*; D009130:Muscle, Smooth / Q000201:enzymology* / Q000502:physiology; D010052:Ovariectomy; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000201:enzymology*; D054460:rho-Associated Kinases
D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases