Journal
AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY
Volume 290, Issue 3, Pages F650-F656Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajprenal.00235.2005
Keywords
urinary bladder dysfunction; calcium sensitization; hyperglycemia
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Funding
- NIDDK NIH HHS [DK 55042, P50 DK 52620, P50 DK052620-05, P50 DK052620-040002, P50 DK052620-050002, P50 DK052620-030002] Funding Source: Medline
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Urinary bladder dysfunction caused by the alteration of detrusor smooth muscle ( DSM) is one of the complications of diabetes. It is well established that smooth muscle contractility is regulated by an elevation of cytosolic Ca(2+) via myosin light chain ( MLC) phosphorylation. However, recent studies have shown the modulation of MLC phosphorylation without a rise in Ca(2+) in smooth muscle and that two key molecules ( Rho-kinase and CPI-17) are involved in the regulation of calcium sensitization. This study investigates the effect of diabetes on DSM calcium sensitization. Diabetes was induced by alloxan in New Zealand White rabbits, and age-matched rabbits given 5% sucrose in the drinking water served as control for diuresis. Two-dimensional gel electrophoresis showed that basal MLC phosphorylation level was significantly higher in diabetic animals than normal or diuretic controls, and Rho-kinase-specific inhibitor, Y-27632, decreased MLC phosphorylation level. Adding Y-27632 to bethanechol-precontracted DSM strips can induce muscle relaxation, but it occurred much more slowly in diabetic samples compared with controls. RT-PCR, Western blot analysis, and immunohistochemistry revealed the overexpression of Rho-kinase beta and CPI-17 at both mRNA and protein levels in response to diabetes. In conclusion, our results demonstrate that Rho-kinase contributes to DSM MLC phosphorylation and there is a higher basal MLC phosphorylation level in diabetic DSM. Our results also suggest that this high basal MLC phosphorylation may be due to the upregulation of Rho-kinase and CPI-17. Thus Rho-kinase-and CPI-17-mediated Ca(2+) sensitization might play a role in diabetes-induced alteration of the detrusor contractility and bladder dysfunction.
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