Effects of spermine on the relaxation response of rat detrusor smooth muscles.
Endogenous polyamines are known to influence excitation-contraction coupling in smooth muscle. This study was designed to determine the effects of the polyamines spermine, spermidine, and putrescine on the contractile responses of rat detrusor smooth muscles. Under physiological conditions, isometric tension recordings were made of isolated bladder strips from excised rat bladder. The effects of spermine, spermidine, and putrescine (1 mM each) on the bladder contractions induced by various agents, i.e., acetylcholine, bethanechol, high-K, and tetraethylammonium (TEA) were measured. A conventional patch clamp technique was used in whole cell mode with single smooth muscle cells of rat bladder. Calcium channel currents were recorded to determine the effects of spermine on channel activities. Polyamines elicited a concentration-dependent relaxations on the contractile agents induced contractures. Spermine showed the most potent relaxation effect of the polyamines examined, and relaxed the contractions induced by the agents. Calcium channel activities were significantly reduced by adding 1 mM spermine to the bath. We concluded that spermine exerts a potent relaxant effect on rat bladder smooth muscle, and this effect appears to be mediated by calcium channel antagonism.
Myung
Soon Chul
SC
Department of Urology and Physiology, Chung-Ang University, College of Medicine, Dongjak Gu, Huksuk Dong 221, Seoul, South Korea.
Oh
Seung Young
SY
Kim
Kyung Do
KD
Kim
Sae Chul
SC
Lee
Moo Yeol
MY
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects*; D009129:Muscle Tonus / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D011700:Putrescine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology*; D019789:Tetraethylammonium / Q000494:pharmacology; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects / Q000502:physiology