신생 백서에서 급성 일산화탄소 중독이 Myelin 표식 효소인 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase)에 미치는 영향

Abstract

[한글]

2'3'=cyclic nucleotide 3'-phosphophdrolase (CNPase ; EC 3.1.4.37)는 중추 신경 조직에서 oligidendroglical cell과 myelic 조직에 높은 활성도로 특유하게 존재하는 myelin의 특수한 생화ㅎ가적 표식 효소로서 신생 쥐나 생쥐에서 myelin 형성 시기와 정확하게

일치하여 급속하게 증가하므로 중추신경계 myelination 과정에 대한 생화학적인 표식 및 양적인 척도로서 사용되는 효소이다. 급성 일산화탄소 중독이 중추 신경계의 myelin 합성 과정에 미치는 영향을 일차적으로 관찰하기 위하여 myelin 합성이 왕성하게 일어나는 시

기에 있는 신생쥐에 (생후 12일, 15일, 17일, 21일, 24일) 급성적으로 일산화탄소 중독을 7시간 동안 유발시켜 혈중 HbCO 농도를 40-70%로 유지시켰을 때 총 뇌균질액 내 CNPase 효소 활성도의 변화 및 효소 활성도의 회복등을 관찰하고자 본 실험에 착수하여 다음과 같은 결론을 얻었다.

1. 정상군 신생 백서(생후 12일, 15일, 17일, 21일, 24일, 26일,29일)에서 측정한 CNPase의 specific activity는 각각 0.40±0.0852, 1.01±0.0814, 2.30±0.1526, 2.60±0.306

5, 2.91±0.0959, 3.06±0.1102, 3.12±0.2005 moles/min/mg protein으로서 생후 12일부터 17일까지 급격한 증가를 보였고 17일부터 24일까지는 완만한 증가 경향을 보였으며 26일, 29일째는 거의 평형 상태를 유지함을 관찰하였다.

2. 생후 12일의 신생백서에 7시간 동안의 급성 일산화탄소 중독을 유발시켰을 때 CNPase 활성도는 정상군과 거의 동일하여였으나 회복 2일군, 5일군, 9일군에서 증가한 효소 활성도는 정상군에서 증가한 효소 활성도와 비교할 때 현저히 감소되어 회복 5일군에서는 52.2%, 회복 9일군에서는 33%의 감소를 보였으며 동일군에서 brainso 평성된 총 단백질의 양도 효소 활성도의 감소와 비슷한 경향으로 감소되었으나 회복기간 동안 서서히 증가하는 경향을 보였다.

3. 생후 15일의 신생 백서에서 7시간 동안의 급성 일산화탄소 중독은 CNPase의 활성도를 변화시키지 않았으며, 회복 2일군, 5일군, 10일군에서 증가한 효소 활성도는 생후 12일의 백서에서처럼 정산군의 효소 활성도의 증가와 비교할 때 현저히 감소되어 회복 5일군에서는 정상군의 31%, 회복 10일군에서는 20%의 감소를 보였으나 회복기간동안 서서히 재생되는 경향을 관찰하였다.

4. 생후 17일과 21일 그리고 24일된 백서에서도 7시간 동안의 급성 일산화탄소 중독은 CNPase의 활성도를 변화시키지 않았으며 이들 회복군에서는 해당 정상군에서와 비슷한 효소 활성도를 유지하면서 증가함을 관찰하였다.

5. 생후 15일의 백서에 매일 3시간씩 6일동안 그리고 9일 동안에 걸쳐 반복적인 CO 중독을 시킨 실험군에서도 CNPase 활성도는 정상군보다는 감소하였으나 서서히 증가함을 보였다.

이상의 결과로 미루어 신생 백서에서 특히 생후 12일과 15일의 백서 뇌에서 일산화탄소 중독은 중독이후 회복기에 CNPase 활성도를 현저하게 감소시켰으며 이는 초기 myelin 합성을 감소 또는 지연시킴 것으로 사료되며 이에 관여하는 기전은 아마도 일산화탄소 중독

에서 유발되는 저산소증이 oligodendrocytes의 증식과 분화과정을 억제함으로써 초래되는 결과로 사료된다.

The Effect of Acute Carbon Monoxide Intoxication on the Neonatal Rat Brain 2',3'

-cyclic uncleotide 3'-phosphohydrolase

Seong Gyu Hwang

Department of Medical Science, The Graduate School Yonsei University

(Directed by Prof. Yoon Soo Kim, M.D.,Ph.D.)

The enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase:EC 3.1.4.37) is

present at high specific activity in myelin and in oligodendrocytes which

synthesize and maintain myelin in the central nervous system. In the brains of

neontal rats and mice, the activity of CNPase increases exactly in accordance to

the period of brain myelination. CNPase is, therefore, considered to be the

specific biochemical markers for myelin and oligodendrohlia. The close relationship

between the activity of CNPase and nyelinogenesis has been established well. The

purpose of this study was to investigate the effect of acute carbon monoxide

intoxicateion on the activity of CNPase in the neonatal rat brain.

1. The specific activities of CNPase in the brains of normal neonatal rats 12,

15, 17, 21. 24, 26 and 29 days old were measured and the results showed that the

activities were increased most rapidly during the ages of 12 and 17 days. However,

during the period of 17 and 24 days old, a slow increment in enzyme activity was

observed and the activities reached the plateau through the age of 26 and 29 days.

2. When the 12 days old rats were acutely intoxicated with carbon monoxide for 7

hrs maintaining the blood concentration of HbCO as 40-70%, the activities of brain

CNPase were not changed compared to the normal, however, the recovery of the enzyme

activity was considerably retarded compared to the normal. The reduction of enzyme

activity was 52.2% in the group of five days recovery and 33% in the group of nine

days recovery after CO intoxication. The total protein content of brain was

decreased in a similar way to the reduction of enzyme activity.

3. The activity of 15 days old rat brain CNPase after 7 hur intoxication was not

changed compared to the normal. However, the recovery of enzyme activity was

considerably retarded compared to the normal. The reduction of enzyme activity was

about 31% in the group of five days recovery and 20% in the group of 10 days

recovery after CO intoxication.

4. Acute carbon monoxide intoxication for the period of 7 hrs did not cause any

changed in the activities of brain CNPase in rats of 17, 21 and 24 days old. In

these groups of rats, the retarded recovery of enzyme activity after acute

intoxication which was shown in the group of rats of 12 and 15 days old was not

apparent.

5. When the 15 days old rats were subjected to a repeated 3 hrs daily

intoxication of CO for 6 days and 9 days, a slow increment of CNPase activity was

shown although the enzyme activities of both groups decreased considerably compared

to the normal. The results, so far, suggest that in the neonatal rat brain,

particularly, in 12 and 15 days old rats, acute carbon monoxide intoxication caused

significant reduction of specific activity of CNPase, therefore, it may cause

reduction or retardation of the early myelinogenesis. The mechanism involved in

this may be explained by the reduced oligodendroglial preliferation and

differentiation caused by carbon monoxide induced cerebral hypoxia. The possibility

of permanent damage of the cells can not be explained from this study.

[영문]

The enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase:EC 3.1.4.37) is present at high specific activity in myelin and in oligodendrocytes which synthesize and maintain myelin in the central nervous system. In the brains of

neontal rats and mice, the activity of CNPase increases exactly in accordance to the period of brain myelination. CNPase is, therefore, considered to be the specific biochemical markers for myelin and oligodendrohlia. The close relationship between the activity of CNPase and nyelinogenesis has been established well. The purpose of this study was to investigate the effect of acute carbon monoxide intoxicateion on the activity of CNPase in the neonatal rat brain.

1. The specific activities of CNPase in the brains of normal neonatal rats 12, 15, 17, 21. 24, 26 and 29 days old were measured and the results showed that the activities were increased most rapidly during the ages of 12 and 17 days. However, during the period of 17 and 24 days old, a slow increment in enzyme activity was observed and the activities reached the plateau through the age of 26 and 29 days.

2. When the 12 days old rats were acutely intoxicated with carbon monoxide for 7 hrs maintaining the blood concentration of HbCO as 40-70%, the activities of brain CNPase were not changed compared to the normal, however, the recovery of the enzyme

activity was considerably retarded compared to the normal. The reduction of enzyme activity was 52.2% in the group of five days recovery and 33% in the group of nine days recovery after CO intoxication. The total protein content of brain was decreased in a similar way to the reduction of enzyme activity.

3. The activity of 15 days old rat brain CNPase after 7 hur intoxication was not changed compared to the normal. However, the recovery of enzyme activity was considerably retarded compared to the normal. The reduction of enzyme activity was about 31% in the group of five days recovery and 20% in the group of 10 days

recovery after CO intoxication.

4. Acute carbon monoxide intoxication for the period of 7 hrs did not cause any changed in the activities of brain CNPase in rats of 17, 21 and 24 days old. In these groups of rats, the retarded recovery of enzyme activity after acute intoxication which was shown in the group of rats of 12 and 15 days old was not apparent.

5. When the 15 days old rats were subjected to a repeated 3 hrs daily intoxication of CO for 6 days and 9 days, a slow increment of CNPase activity was shown although the enzyme activities of both groups decreased considerably compared

to the normal. The results, so far, suggest that in the neonatal rat brain, particularly, in 12 and 15 days old rats, acute carbon monoxide intoxication caused significant reduction of specific activity of CNPase, therefore, it may cause reduction or retardation of the early myelinogenesis. The mechanism involved in this may be explained by the reduced oligodendroglial preliferation and differentiation caused by carbon monoxide induced cerebral hypoxia. The possibility of permanent damage of the cells can not be explained from this study.