Calcium이 흰쥐 취절편의 효소분비에 미치는 영향

Abstract

[한글]

취효소분비자극소인 acetylcholine과 cholecystokinin으로 인한 효소분비는 세포내 Ca**++ 농도증가와 관련이 있다. Ca**++은 분비과정에서 second messenger로서의 역할이 주이며 세포내 Ca++과 아울러 세포외 Ca++모두 분비과정에 중요하다고 주장되고 있다. 취효

소 자극분비에 세포내 유리 Ca**++농도증가는 인정되는 현상이나 이 활동형 Ca**++의 근원에 관한 견해는 아직 인지된 바 없다. 이번 실험에서는 흰쥐의 취장절편을 이용하여 세포의 Ca++ 농도변동이 취효소의 기초분비 및 acetylcholine 자극분비에 미치는 영향을 관

찰하여 취효소분비에 관한 Ca++의 역할을 검토하고자 하였다.

실험동물로는 체중 78∼100 g 되는 어린 흰쥐를 암수구별없이 사용하였고 각 동물을 희생시킨 후 취장의 uncinate 엽을 적출하여 Krebs-Ringer bicarbonate buffer (KRBB)에서 acetylcholine 10**-6M로 자극하여 amylase 유리를 관찰하였으며 이때 incubation media

내의 Ca**++농도를 가감하여 그 효과를 검색하였다.

실험성적을 요약하면 다음과 같다.

1. 흰쥐 취장절편은 휴식기에서도 일정한 amylase 기초유출을 나타냈고 acetylcholine 10**-6 M의 반복자극으로 일정한 amylase 분비증가가 나타났다.

2. Incubation media에 Ca**++ 농도를 증가시키면 용량에 따라 amylase의 기초분비와 acetylcholine 자극분비가 항진되나 고농도인 Ca**++ 10.5mM에서는 자극분비가 오히려 감소하였다.

3. Incubation media의 Ca**++ 농도를 감소시키면 amylase 기초유출은 변동이 없으나 acetylcholine 자극분비는 용량비례로 감소되었다.

4. Ca**++ 배제 media에서는 amylase 기초유출은 대조군과 비슷하였으나 acetylcholine 자극에 의한 amylase 분비는 처음에만 증가될뿐 반복자극으로는 기초유출치와 차이가 없었다.

이상의 성적으로 보아 취장효소의 기초유출에는 세포외 Ca**++ 이 큰 역할을 못하나 자극분비에 있어서는 세포내 Ca**++이 초기분비에 관여하고 지속자극분비에는 세포외 Ca**++이 주로 이용된다고 추측하는 바이다.

Effect of Calcium on the Enzyme Release from the Pancreatic Slices of Baby rat

Jae Byung Choi

Department of Medical Science The Graduate School Yonsei University

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

Calcium ion plays an important role in the secretory mechanism of exoorine

pancreas. Stimulation of cholinergic or cholecy stokinin receptors of pancreatic

acinar cells results in enzyme secretion. This stimulus-secretion coupling is

believed to involve an increase in the concentration of cytoplasmic free calcium.

The first consequence of receptor-binding is a rapid increase in the

concentration of cytoplasmic calcium, which is believed to be the result of calcium

release from intracellular stores. Although the initial secretion of pancreatic

enzymes seems dependent upon this calcium, prolonged enzyme release requires the

additional presence of extracellular calcium. In addition, extracellular calcium

might be of importance for the secretory process influencing the state of the

plasma membrane where these events take plate. Therefore, present study was

undertaken to clarify the role of extraoellular calcium on the basal and

acetylcholine stimulated enzyme secretion of pancreas.

Baby rats weighing 70-100g of either sex were used. After decapitationl uncinate

process of pancreas was isolated . The pieces of pancreas were incubated in

Krebs-Ringer bicarbonate buffer and the enzyme secretions were stimulated with

acetylchhopine(10**-6 M). The effects of increasing or decreasing the Ca**++

concentration of the incubation media on the basal and acetyionoline stimulated

enzyme secretion were observed.

The results obtained are summarized as foIlows :

1. The basal amylase release from the pancreatic slice was fairly constant, and

repeat stimulation with acetylsholine (10**-6 M) increased the amylase release and

reached platateau within 10 min.

2. Addition of calcium in the incubation media inoreased both basal and

stimulated amylase releases in a dosedependent manner. However, higher

concentration of calcium(10.5mM) inhibited the stimulated amylase release.

3. Reducing the Ca**++ concentration of the incubation media, the stimulated

amylase release decreased in a dose-dependent manner, but there were no changes in

basal amylase release.

4. In calcium-free incubation media, the stimulated amylase release was

transiently increased during the first 10 min of stimulation, and thereafter

dropped to the basal level. The basal amylase release was not changed in

calcium-free incubation media.

From the above results it is suggested that intracellular calciums are utilized

in the basal enzyme secretion and the initial phase of stimulated secretion of

pancreas, however the extracellular calciums are important for the sustained

stimulation of pancreatic enzyme secretion.

[영문]

Calcium ion plays an important role in the secretory mechanism of exoorine pancreas. Stimulation of cholinergic or cholecy stokinin receptors of pancreatic acinar cells results in enzyme secretion. This stimulus-secretion coupling is believed to involve an increase in the concentration of cytoplasmic free calcium.

The first consequence of receptor-binding is a rapid increase in the concentration of cytoplasmic calcium, which is believed to be the result of calcium release from intracellular stores. Although the initial secretion of pancreatic enzymes seems dependent upon this calcium, prolonged enzyme release requires the additional presence of extracellular calcium. In addition, extracellular calcium might be of importance for the secretory process influencing the state of the plasma membrane where these events take plate. Therefore, present study was undertaken to clarify the role of extraoellular calcium on the basal and

acetylcholine stimulated enzyme secretion of pancreas.

Baby rats weighing 70-100g of either sex were used. After decapitationl uncinate process of pancreas was isolated . The pieces of pancreas were incubated in Krebs-Ringer bicarbonate buffer and the enzyme secretions were stimulated with

acetylchhopine(10**-6 M). The effects of increasing or decreasing the Ca**++ concentration of the incubation media on the basal and acetyionoline stimulated enzyme secretion were observed.

The results obtained are summarized as foIlows :

1. The basal amylase release from the pancreatic slice was fairly constant, and repeat stimulation with acetylsholine (10**-6 M) increased the amylase release and reached platateau within 10 min.

2. Addition of calcium in the incubation media inoreased both basal and stimulated amylase releases in a dosedependent manner. However, higher concentration of calcium(10.5mM) inhibited the stimulated amylase release.

3. Reducing the Ca**++ concentration of the incubation media, the stimulated amylase release decreased in a dose-dependent manner, but there were no changes in basal amylase release.

4. In calcium-free incubation media, the stimulated amylase release was transiently increased during the first 10 min of stimulation, and thereafter dropped to the basal level. The basal amylase release was not changed in calcium-free incubation media.

From the above results it is suggested that intracellular calciums are utilized in the basal enzyme secretion and the initial phase of stimulated secretion of pancreas, however the extracellular calciums are important for the sustained

stimulation of pancreatic enzyme secretion.