Effects of MBCQ, phosphodiesterase type 5 inhibitor, on high K+-induced contraction and cytosolic Ca2+ level in guinea pig urinary bladder
2003
Kaneda, T. (Nippon Veterinary and Animal Science Univ., Musashino, Tokyo (Japan)) | Fukuda, T. | Shimizu, K. | Urakawa, N. | Nakajyo, S.
ABSTRACT We have examined the effects of MBCQ, a phosphodiesterase type 5 inhibitor, on high K+ -induced contraction and cytosolic Ca2+ ([Ca2+] sub i) level in guinea pig urinary bladder and compared with those of zaprinast. In fura2-loaded muscle strips, MBCQ and zaprinast inhibited the high K+ (hyperosmotically added 65mM KCl) -induced contraction in a concentration-dependent manner. MBCQ and zaprinast both inhibited the K+ (isosmotically added 77mM KCl) -induced contraction and the increases in [Ca2+] sub i level in a concentration-dependent manner. Although the inhibitory effects of zaprinast in [Ca2+] sub i level was smaller than that in muscle contraction, MBCQ inhibited muscle contraction and [Ca2+] sub j level in the same degrees. In summary, it is suggested that the relaxation mechanism of MBCQ is different that of zaprinast and MBCQ inhibit the high K+ -induced contraction via the decreases of Ca2+ movement.
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