지속분비 자극이 취효소 배출에 미치는 영향

Abstract

[영문]

[한글]

취장 외분비는 secretin으로 분비 촉진이, pancreozymin 및 미주신경 자극으로 효소 분

비촉진이 유발된다.

취 효소단백은 endoplasmic reticulum의 ribosome에서 합성되어 강내로 이동하고 smoot

h surfaced vacuole을 거쳐 완전한 zymogen granule을 형성하여 저장되었다가 분비 자극

으로 세포외로 배출된다고 생각되어 왔다. 요사이는 효소단백 배출이 zymogen granule에

서 뿐만 아니라 cytoplasm에서도 일어나며 이는 기능적으로 서로 다른 pool이 있기 때문

이라고 생각한다(Rothman and Isenman, 1974).

Liebow와 Rothman(1975)은 3H-chymotrypsinogen의 장내 주입으로 수분후에 취액에서 3H

-Chymotrypsinogen을 발견할 수 있어 분비된 취효소의 일부가 장에서 흡수되어 다시 취장

을 통해 분비되는 소화효소의 장취 순환이 이루어질 것이라고 주장하였다.

이상의 견해를 더 추구하고져 체중 27g 내외의 토끼를 사용하여 취외분비 변동 및 정맥

내 취액 재투여로 인한 영향을 검색하였다. 체중 kg당 매시간 secretin lu와 CCK-PZ 2u

또는 acetylcholine 0.3mg을 정맥내 주입하였으며 취관에는 polyethylenetube를 삽입하며

20분 간격으로 취액을 받았다. 취액 재주입군은 1회 채취액을 5회 채취때, 2회 채처액은

6회때 등으로 각각 정맥내 주입하였다. 실험 종료후 취장을 적출하여 조직내 효소활성을

측정하였다.

실험 결과를 요약하면 다음과 같다.

1. Secretin과 pancreozymin을 계속 정맥내 주입하므로 취액분비는 높은 치를 유지 하

나 취단백 및 취효소치는 조기상승 후 계속적인 자극에도 불구하고 시간 경과에 따라 철

저히 저하 되었다.

2. Secretin과 acetylcholine의 계속 정맥내 주입 실험에서도 취액분비는 지속적인 높

은 치를 보이나 취단백 및 효소분비는 조기 증가 반응 후 시간 경과에 따라 현저히 저하

되었다.

3. 취효소 분비가 저하된 시기에 다른 분비 자극 pancreozymin주입 자극예에서는 acetr

lcholine, acetylcholine 주입시엔 pancreozymin을 주면 취효소 분비 증가를 나타내었다.

4. 취액을 정맥내 투여한 실험예의 효소분비치는 취액을 투여 않은 예보다 증가하였다.

5. 취조직내 효소량은 secretin과 acetylcholine 자극으로 감소를 나타냈으나 secretin

과 pancreozymin 자극예 에서는 오히려 약간 증가하였다. 그러나 정맥내 취액 주입으로는

별변동이 없었다.

이상의 실헙성적을 종합해 보면 취효소 단백의 일부는 혈행에서 취선포를 통하여 장내

로 재분비 되는 장취순환을 한다고 생각되며 pancreozymin 자극 또는 acetylcholine 자극

으로 분비되는 서로 다른 취효소 fool이 취선포내에 있는지는 더욱 추구해 볼 과제로 생

각된다.

Effect of continuous stimulation on the pancreatic enzyme secretion

Young Sook Pae, M.D.

Department of Medical Science The Graduate School, Yonsei University

(Directed by Professor Sa Suk Hong, M.D)

Two hypotheses are suggested as secretory mechanism of digestive enzymes from

exocrine pancreas. One of them is classical Palade's packaging-exocytosis theory,

in which the enzymes synthetized in the ribosomal complex are packaged into zymogen

granules and migrates to the apex of the cell where its contents are secreted by

stimulation.

Alternate hypothesis, i.e. equilibrium theory. was recently proposed by Rothman

and his co-workers. In this model digestive enzymes move bidirectionally through

specialized membranes, so that enzyme in various compartment can be in

"equilibrium" with each other. The cytoplasm acts as rapidly equilibrating pool

(REP) and zymogen granule as slowly equilibrating pool (SEP).

Recently Rothman and his co-workers suggested that at least some digestive

enzymes undergoes an enteropancreatic circulation, similar to the enterohepatic

circulation of bile salt : that is, intact digestive enzyme molecules are absorbed

by the intestine and circulated by way of the blood stream to acinar cell. Finally

the enzyme molecules are secreted back into the intestine.

Present study was undertaken to investigate the changes of secretory functions by

continuous stimulation and the intravenous homologous enzymes could he resecreted

via the pancreas in rabbits.

The albino rabbits of broth sexes weighing 2.0-2.5kg were used and anesthetized

with secobarbital(30mg/kg). After catheterization into femoral vein and pancreatic

duct of the rabbit, secretin (1u/kg/hr) with either cholecystokinin-pancreozymin

(CCK - PZ,2u/kg/hr)or acetylcholine (0.3mg/kg/hr) was infused Constantly

(12ml/kg/hr) by Harvard infusion pump.

The pancreatic juice was collected every 20 minutes, and protein and amylase

activity were determined by spectrophotometrically at 280 nm and by Sumner method,

respectively. In the experiment of re-infusion of pancreatic juice the first juice

was injected at the time of 5th collection and the Second juice at 6th collection,

and so on

The results obtained are summarized as fellows.

1. The flow rate of the pancreatic secretion was relatively constant by

continuous infusion of secretin with either pancreozymin or acetylcholine.

2. Both proteins and amylase contents were increased markedly and then

progressively defreaaed by continuous stimulation with pancreozymin or

acetylcholine in animals under secretin infusion and at the end of 4 hour-infusion

the enzyme proteins were reduced nearly to the level of saline control.

3. At the end of 4 hour-infusion, when the protein enzyme levels were decreased

markedly. alternative secretory stimulus, i,e. pancreozymin in acetylcholine

infusion or acetylcholine in pan creozymin infusion, increased significantly the

protein and amylase secretion.

4. After intravenous injections of own pancreatic juice, the pancreatic protein

and amylase levels were showed relative increases and consequently the decreasing

levels of both the protein and amylase were over riden. Nevertheless, flow rates of

pancreatic juice were not changed.

7. The enzyme contents of pancreatic tissue after 4 hour-stimulation were

decreased in concomittant secretin-acetylcholine stimulation but not changed in

secretin-pancreosymin stimulation.

By these findings it is conceived teat at least some digestive enzymes can be

resecreted via pancreas from blood stream to intestine and it should further

investigated Whether the acetylcholine-responding or pancreozymin-responding pools

are present in the pancreas.