The Charateristics of Glycogen Metabolism of Diaphragm in Rats

운동부하시 흰쥐 호흡근의 당원 대사

Diaphragm is thought to play the most important role in breathing and has a substantially greater proportion of slow oxidative and fast glycolytic fibers, and low proportion of fast oxidative fibers. The respiratory muscle, diaphragm, has the functional characteristics of slow speed of contraction, high resistance to fatigue and the ability to respond to intermittent ventilatory loads, for example of exercise. In the present study, the characteristics of the metabolism (depletion and repletion) of glycogen and the structural changes of diaphragm during depletion and repletion of glycogen were observed in rats. For comparison, the red gastrocnemius muscle which has a greater proportion of fast oxidative glycolytic (FOG) and slow oxidative (SO) fibers, and low proportion of fast glycolytic (FG) fiber, was also studied. The glycogen concentration of diaphragm in overnight fasted rats was $2.30{\pm}0.14mg/gm$ wet weight. The values of glycogen concentration at 60, 90 and 120minutes of treadmill exercise loaded rats was significantly decreased compared to that of the overnight fasted rats. There was no significant difference among the glycogen concentrations of diaphragm at 60, 90 and 120minutes of exercises. The glycogen concentration of diaphragm was decreased to $1.12{\pm}0.17$ from $2.30{\pm}0.14mg/gm$ wet weight by treadmill exercise. The glycogen depletion rate of diaphragm during exercise was faster than that of red gastrocnemius in both of the first 60minutes and 120minutes duration of exercise. The glycogen repletion of diaphragm after intragastric glucose administration by stomach tube was studied in control and exercise groups. The glycogen concentration was significantly increased after glucose administration in both of control and exercise groups. All of the concentration of exercise group at 60, 120 and 180minutes after glucose administration was significantly higher than those of control group. In conclusion, one of the characteries of diaphragm in glycogen metabolism is fast glycogen depletion during exercise, and slowness of glycogen repletion after glucose ingestion in rats.

생리적 특성이 독특한 횡경막의 운동시 당원이 용양상과 운동 후 경구 투여한 당이 당원으로 재축적되는 과정을 적색비복근과 비교하여 횡경막의 생리적 특성의 일단을 규명하고자 시도한 연구 결과를 요약하면 다음과 같다. 대조군에서 횡경막의 당원농도는 적색비복근보다 높은 경향을 보였으며, 운동군에서 운동부하 첫 1시간에 횡격막의 당원농도는 약 1/2로 감소하였고 그 후 지속되는 1시간동안에는 별 차이를 보이지 않았으며 적색비복근의 당원농도와는 유의한 차이를 발견할 수 없었다. 그러나 당원 감소속도를 분석한 결과 횡격막이 적색비복근보다 빠른 경향을 보였다. 횡격막의 당원 재축적량 및 재축적속도를 분석한 결과 운동부하군에서 최대축적량은 적색비복근보다 낮았으며 재축적속도는 대조군에서는 양근에서 비슷하였으나 운동부하군에서는 적색비복근이 빨랐다. 당투여에 의한 골격근의 당원축적은 주로 근원섬유사이에 분포함을 전자현미경 관찰을 통해서 알 수 있었다. 이상의 결과로 미루어보아 횡격막은 운동부하시 당원의 소모는 비교적 빠른 경향이었으나 당투여에 의한 재축적은 느린 것을 알 수 있었다.