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KMID : 0360419780140010033
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Korean Journal of Pharmacology
1978 Volume.14 No. 1 p.33 ~ p.40
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Age-dependent Changes in Contraction and Relaxation of Ureteral Smooth Muscle in Guinea pig
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Abstract
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1) The authors studied the effect of increasing age on the contraction and relaxation mechanism in the ureteral smooth muscle of the guinea pig.
2) Two to three week old, three month old, and two to three year old guinea pig ureters were used and the consistent amplitude of contratile responses were induced by using train stimulation.
3) After mounting the specimens in Tyrode´s solution containing 2.6mM Ca^(++), the ureter was stimulated, of which amplitude was initial contraction and next continuously superfused with Ca^(++)-free Tyrod´s solution. When the contractile response stopped by electrical field stimulation, the muscle specimens was superfused with Tyrode´s solution 0.25mM Ca^(++) for 15min and stimulated with the same parameters. Thereafter, the contraction of Ca^(++) in the solution was increased step by step up to 2.7mM.
4) The ureters of 2-3 week old guinea pigs needed less Ca^(++) for the recovery of contractile response than those of three month and two to three year old did. In 2.7mM Ca^(++), the ureters of 2-3 week and 3 month old guinea pigs recovered the contractile response of over 90% but those of 2-3 year old recovered the contractility of 77.2%.
5) Isoproterenol inhibited in dose dependent manner from 10^(-7) to 10^(-5) M ureteral contractility of both 2-3 week and 2-3 year old guinea pigs. The inhibition of the old ureter by isoproterenol was significantly less (P<0.025) than that of the younger ureter. However theophylline showed the strong inhibition independent of the function of age.
6) Dibutyryl cyclic AMP showed dose-dependent inhibition of the contraction of ureters of 2-3 week old guinea pigs but there was shown no inhibition in the old ureters. Further, the content of endogenous cyclic AMP in the two week old ureter was higher by 73% than that of 17 month old ureter. Cyclic GMP contents was not much different between two groups.
7) The ureteral smooth muscle of the younger guinea pig had more efficiency than that of the older animals in the mobilization and storage of calcium which concerned itself in the contraction and relaxation mechanism.
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