성숙흰쥐와 비교한 신생흰쥐 방광평활근에서 반복적인 수축으로 유발된 방광근 피로도의 차이
Comparative Studies on the Fatigue of Urinary Bladder following Repeated Contractions in Neonatal and Adult Rats
소속 상세정보
오승준/Seung June Oh
김성준/김기환/이안기/김광명/최황/Sung Joon Kim/Ki Whan Kim/Ahn Kie Lee/Kwang Myung Kim/Hwang Choi
KMID : 0358319990400020207
Abstract
서론
장기가 형성되고 난 뒤 제대로 성숙과정을 거치지 않은 발육 신생아기의 방광생리는 성인
의 그것과는 많은 차이가 있을 것이라고 많은 사람들이 수긍하고 있지만 신생아기의 방광생
리에 관해서는 아직 많은 연구정보를 접할 수는 없는 상황이다. 또한 골격근에서의 근육피
로 현상에 관해서 는 스포츠의학 등 많은 분야에서 활발히 연구되어 왔지만, 평활근에 대해
서는 연구결과가 많지 않다.
방광출구폐색과 같은 하부요로에 하중이 가해지는 상황의 초기에 방광은 출구저항을 이겨
보려고 반복적인 수축을 하게 되지만 폐색이 제거되지 않으면 결국 보상에 실패하는데
(decompensation) 이러한 상황에서 평활근의 피로가 발생될 수 있다고 생각된다.
본 연구에서는 신생아기의 방광평활근이 성인기의 방광평활근에 비교하여 보아 이러한 피
로 반응에 있어서 생리적 차이를 알아보고자 하였다.
Purpose : The function of urinary bladder in neonate and adult are regarded as
different but little is investigated on the physiological function of the neonatal urinary
bladder In this study, we compared the contractile responses of bladder muscle strips
between neonate and adult rats to repeated electrical field stimulations(EFSs).
Materials and Methods : Postnatal 1 to 3-day-old Sprague-Dawley(SD) rats(7.3±
1.59m, mean±SE, n=15) and 12-week-old adult SD rat(386±21gm, n=15) were sacrificed
and longitudinal strips of the anterior wall of the bladder were prepared. Each
preparation was mounted in a vertical chamber and connected to a force transducer
(FT03, Grass, U.S.A.). Isometric contractions were induced by three different methods;
1) intrinsic nerve activation by applying EFSs(5, 20, or 60㎐ frequency, square pulse of
0.8ms width, 70V/㎝, 2.5s duration) every 50 seconds, 2) the activation of muscarinic
receptors on smooth muscle cell membrane with 5.0μM carbachol(CCh), 3) direct
smooth muscle stimulation by applying EFSs(60㎐ frequency, 50㎳ width, 70V/㎝, 2.5s
duration) in the presence of tetrodotoxin every50 seconds.
Results : Contractile responses to intrinsic nerve stimulations reached maximal
amplitude at 60㎐ stimulation in both adult and neonate rat bladder. Recovery from the
fatigue in neonate and adult bladder muscle was evaluated by the amplitude changes in
contractions evoked by EFS with 3 min. or 1 min. rest periods. Poor recovery was
induced in neonates even by 3 min. rest period. In neonate group, the amplitude of
contractions declined gradually (fatigue response) with 20 and 60㎐ stimulations, while
the fatigue responses were negligible in adult group. The responses to the exogenous
CCh before and immediately after the repeated stimulations were not significantly
different in both groups. Repeated direct muscle stimulations did not induce significant
decreases of contractile responses in both groups.
Conclusions : These results demonstrate that neonatal bladder becomes fatigued faster
than adult bladder and the fatigue seems to occur at pre-receptor level of the smooth
muscle cells rather than at the muscle itself.
키워드
Fatigue; Bladder; Smooth muscle; Carbachol; Neonate;
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