Premium
Mechanism of Exocrine Pancreatic Insufficiency in Streptozotocin‐Induced Type 1 Diabetes Mellitus
Author(s) -
PATEL REKHA,
SHERVINGTON AMIL,
PARIENTE JOSE A.,
MARTINEZBURGOS MARIA A.,
SALIDO GINES M.,
ADEGHATE ERNEST,
SINGH JAIPAUL
Publication year - 2006
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1372.038
Subject(s) - medicine , endocrinology , cholecystokinin , streptozotocin , amylase , pancreas , diabetes mellitus , basal (medicine) , insulin , stimulation , chemistry , enzyme , receptor , biochemistry
Diabetes mellitus (DM) is a major health problem at present affecting about 180 million people worldwide. DM is associated with many metabolic abnormalities in the body including the indigestion of carbohydrates leading to malnutrition and weight loss. In this article we investigate the cellular and molecular mechanisms of exocrine pancreatic insufficiency in streptozotocin (STZ, 60 mg kg −1 , i.p.)‐induced DM in male rats compared to healthy age‐matched controls. Either electrical field stimulation (EFS) or cholecystokinin octapeptide (CCK‐8, 10 −8 M) can elicit large and significant ( P < 0.05) increases in amylase output from pancreatic segments compared to basal secretion. Insulin (10 −6 M) alone has no significant effect on amylase output compared to basal but it enhanced the secretory responses to either EFS or CCK‐8. When rats were rendered diabetic with STZ, either EFS or CCK‐8‐evoked amylase output was significantly ( P < 0.01) decreased compared to the responses obtained with either EFS or CCK‐8 alone in healthy age‐matched control pancreas. In addition, CCK‐8 can elicit large dose‐dependent release of amylase in age‐matched control and diabetic acinar cells with significantly ( P < 0.05) reduced responses in diabetic acinar cells. CCK‐8 evoked a large rapid increase in peak cytosolic free calcium concentration ([Ca 2+ ] c ) followed by a decrease to a plateau phase in age‐matched control fura‐2‐loaded pancreatic acinar cells. These responses were significantly ( P < 0.05) decreased in STZ‐induced diabetic acinar cells. In the presence of 10 −6 M insulin, CCK‐8 evoked a much larger increase in the Ca 2+ transient compared to the response obtained with CCK‐8 alone. These effects were significantly ( P < 0.01) inhibited in STZ‐induced diabetic acinar cells. Similarly, in zero extracellular Ca 2+ [Ca 2+ ]ĉ, the CCK‐8‐evoked [Ca 2+ ] c was significantly ( P < 0.05) reduced in both diabetic and age‐matched control acinar cells, but with more pronounced reduction in diabetic acinar cells. CCK A receptor mRNA levels remained unchanged in diabetic rat acinar cells compared to age‐matched healthy control. In contrast, amylase mRNA was significantly ( P < 0.05) reduced in diabetic acinar cells compared to control. The results indicate that reduced amylase secretion in response to either EFS or CCK‐8 in the diabetic pancreas may be due to reduced [Ca 2+ ] c and gene expression for amylase and not to the gene expression of CCK A receptor in pancreatic acinar cells.