Dexamethasone이 흰쥐 태자 간의 형태발생에 미치는 영향

Abstract

[한글]

임신중인 흰쥐에 투여한 dexamethasone(이하 Dexa)이 태자의 간 성숙에 미치는 영향에 관한 지금까지의 연구들은 효소의 활성이나 당원의 함량 등을 취급한 생화학적인 것들이 대부분으로서 Dexa는 태자 간의 당원 함량을 증가시키는 것으로 알려져 있다. 모체에 투

여한 Dexa가 태자의 간에 미치는 영향에 대한 형태학적인 연구는 많지 않으나 이들에 의하면 치료용량의 Dexa는 조혈세포의 수를 감소시키고 성인형 미세구조를 가지는 간세포의 수를 증가시킬 가능성이 많다. 또한 임신 흰쥐에 Dexa를 투여하면 태자의 몸무게 및 여러 장기들의 무게가 감소하고 단백 및 핵산 합성이 감소하며, 간세포의 성숙 및 분화가 촉진된다는 보고가 있는 반면 이와 상반된 연구 결과도 있다.

본 연구에서는 임신 중반 이후의 흰쥐에 Dexa를 투여 횟수 및 총투여량을 달리 복강내로 투여하여 임신 후반기 부터 출생후 2∼4일 까지 각 시기별로 태자 및 신생 흰쥐의 간을 조사하였다. 실험동물로는 54마리의 Sprague-Dawley계 임신흰쥐와 이로부터 얻은 162마리의 태자 혹은 신생 흰쥐를 이용하였으며, Dexa를 투여하지 않은 대조군을 Ⅰ군으로 하고, 임신 흰쥐 몸무게 1g당 10㎍씩 투여한 Dexa 투여횟수에 따라 Ⅱ군(2회 투여), Ⅲ군(3회 투여), Ⅳ군(4회 투여)및 Ⅴ군(5회 투여)으로 나누어, Dexa 총투여량에 따른 몸무게

및 간무게 변동을 조사하고, 광학현미경적 및 전자현미경적 검색을 통하여 조혈세포와 간세포의 분포 및 수와 간세포내 당원 및 지질 축적을 조사하여 간의 성숙 정도를 알아보았다. 또한 bromodeoxyuridine(BrdU)에 대한 면역조직화학적 염색으로 대조군과 Dexa 투여군의 BrdU 표지지수를 구하여 간세포의 중식능을 조사하고, 효소조직화학적 염색으로 히ucose-6-phosphatase(G-6-P)의 활성도를 측정하여 Dexa가 간의 형태발생(성장과 성숙)에 미치는 영향을 조사한 바 다음과 같은 결과를 얻었다.

1. Dexa 총투여량이 많을수록 재태연령 21일 태자의 몸무게, 간무게 및 간무게/몸무게 비가 유의하게 감소하였다.

2. Dexa 투여는 태자 및 신생 흰쥐 간의 조혈기능을 감소시키고 간세포내 공포를 증가시켰다.

3. Dexa 투여는 간세포내 당원, 당-지질 복합체 또는 지질축적을 현저히 촉진시켰으며, Dexa 총투여량이 적은 Ⅱ군에서는 당원 축적이 많고 Dexa 총투여량이 많은 Ⅳ군에서는 지질축적이 많았다.

4. 모든 군에서 재태연령 19일의 간세포 중식능은 매우 높으나 Dexa 투여에 의하여 유의하게 감소하였다.

5. 재태연령 21일의 간세포 중식능은 전반적으로 매우 낮으나 Dexa 총투여량이 많을수록 점차 증가하는 경향을 보였다.

6. 간조직내 G-6-P 활성은 Dexa 투여 여부 및 총투여량과 관계없이 재태연령 19일 및 21일에는 미약하게 나타나고 생후 2일에는 강하게 나타났다. 이상의 결과를 종합하여 보면 임신 흰쥐에 Dexa를 투여할 때 태자의 간세포 중식능이 감소하고 간의 성장이 억제되는 반면, 조혈기능이 감소하고, 당-지질 대사가 촉진되는 것으로 보아 Dexa 투여는 간의 성숙을 촉진하는 것으로 생각된다.

Effects of dexamethasone on morphogenesis of fetal rat liver

Soo-Young Lee

Department of Medical Science The Graduate School, Yonsei University

(Directed by Professor Chan-ll Park )

Numerous biochemical studies on the effects of dexamethasone(Dexa) administered

to pregnat rats showed that dexamethasone stimulated several hepatic and intestinal

enzymes, decreased alpha-fetoprotein, increased hepatic glycogen and accelerated

lung maturation. It is also known that dexamethasone administered to pregnant rat

inhibited the growth of fetal adrenal, liver and lung. In higher concentrations,

dexamethasone retarded fetal rat development, decreasing protein and nucleic acid

content in various fetal orleans. On the other hand, several studies showed that

dexamethasone did not affect the liver development and its DNA synthesis. The

morphological evaluations of dexamethasone effects on fetal liver have been rarely

reported, but one report showed that dexamethasone injected to pregnant rat

accelerated the maturations of fetal rat liver.

In this study 54 female Sprague-Dawley rats and their 162 fetal or newborn rats

were used. Pregnant rats were divided into five groups(Group I: non-treated control

group; Group Ⅱ, Ⅲ, Ⅳ and Ⅴ: dexamethasone treated groups, 2, 3, 4 and 5 doses

of 10㎍ dexamethasone per g body weight of pregnant rats, respectively). The

specimens of liver obtained from fetuses of 17th, 19th and 21th days of gestation

and from newborn rats of 2nd and 4th days of life were examined. The strips of

fiver were used far hematoxylin-eosin(H-E) stain, periodic acid Schiff(PAS) stain,

diastase-PAS(D-PAS) stain, immunohistochemical stain for bromodeoxyuridine(BrdU)

and enzyme histochemical stain for glucose-6-phosphatase(G-6-P). The maturation

indices used in this study were the relative degree of hepatic hemopoiesis and the

development of liver parenchyme. The decree of growth were measured by the changes

of body weight, liver wright, and the ratio of the weight of fiver to

body(liver/body ratio) and BrdU index.

The results are as follows:

1. The weights of body and liver and liver/body ratio of 21-day fetuses decreased

according to the total dose of maternally administered dexamethasone.

2. Dexamethasone decreased the degree of hepatic hemopoiesis and increased

cytoplasmic vacuols in fetal and newborn rat liver.

3. Accumulation of hepatic glycogen and lipid was significantly accelerated in

the Dexa-treatedgroups. For those treated with low dose Dexa(Group Ⅱ) accumulation

of glycogen predominated, while for high-Dexa group(Group Ⅳ) lipid was the

prominent component.

4. BrdU indices of the liver from 19-day fetuses were very high in all groups,

and it was significantly decreased by maternally administered dexamethasone.

5. BrdU indices of 21-day fetal liver were very low, but were slightly higher in

dexamethasone treated groups.

6. There was no difference between the G-6-P activity of control and treated

groups regardless of the dosage.

In conclusion, dexamethasone administered to pregnant rats decreased the growth

of fetal rat livers by reducing the replication capacity represented by BrdU index.

On the other hand, dexamethasone seemed to accelerate the maturation of fetal rat

liver by decreasing hepatic hemopoiesis and stimulating glycogen and lipid

metabolism.

[영문]

Numerous biochemical studies on the effects of dexamethasone(Dexa) administered to pregnat rats showed that dexamethasone stimulated several hepatic and intestinal

enzymes, decreased alpha-fetoprotein, increased hepatic glycogen and accelerated lung maturation. It is also known that dexamethasone administered to pregnant rat inhibited the growth of fetal adrenal, liver and lung. In higher concentrations,

dexamethasone retarded fetal rat development, decreasing protein and nucleic acid content in various fetal orleans. On the other hand, several studies showed that dexamethasone did not affect the liver development and its DNA synthesis. The morphological evaluations of dexamethasone effects on fetal liver have been rarely reported, but one report showed that dexamethasone injected to pregnant rat accelerated the maturations of fetal rat liver.

In this study 54 female Sprague-Dawley rats and their 162 fetal or newborn rats were used. Pregnant rats were divided into five groups(Group I: non-treated control group; Group Ⅱ, Ⅲ, Ⅳ and Ⅴ: dexamethasone treated groups, 2, 3, 4 and 5 doses of 10㎍ dexamethasone per g body weight of pregnant rats, respectively). The specimens of liver obtained from fetuses of 17th, 19th and 21th days of gestation and from newborn rats of 2nd and 4th days of life were examined. The strips of fiver were used far hematoxylin-eosin(H-E) stain, periodic acid Schiff(PAS) stain,

diastase-PAS(D-PAS) stain, immunohistochemical stain for bromodeoxyuridine(BrdU) and enzyme histochemical stain for glucose-6-phosphatase(G-6-P). The maturation indices used in this study were the relative degree of hepatic hemopoiesis and the

development of liver parenchyme. The decree of growth were measured by the changes of body weight, liver wright, and the ratio of the weight of fiver to body(liver/body ratio) and BrdU index.

The results are as follows:

1. The weights of body and liver and liver/body ratio of 21-day fetuses decreased according to the total dose of maternally administered dexamethasone.

2. Dexamethasone decreased the degree of hepatic hemopoiesis and increased cytoplasmic vacuols in fetal and newborn rat liver.

3. Accumulation of hepatic glycogen and lipid was significantly accelerated in the Dexa-treatedgroups. For those treated with low dose Dexa(Group Ⅱ) accumulation of glycogen predominated, while for high-Dexa group(Group Ⅳ) lipid was the prominent component.

4. BrdU indices of the liver from 19-day fetuses were very high in all groups, and it was significantly decreased by maternally administered dexamethasone.

5. BrdU indices of 21-day fetal liver were very low, but were slightly higher in dexamethasone treated groups.

6. There was no difference between the G-6-P activity of control and treated groups regardless of the dosage.

In conclusion, dexamethasone administered to pregnant rats decreased the growth of fetal rat livers by reducing the replication capacity represented by BrdU index.

On the other hand, dexamethasone seemed to accelerate the maturation of fetal rat liver by decreasing hepatic hemopoiesis and stimulating glycogen and lipid metabolism.