Role of the cholecystokinin (CCK)-A receptor in pancreatic growth in rats during the suckling period: a study in a naturally occurring CCK-A receptor gene "knockout" rat.
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Animals↗
Biomedical subjects
A Funakoshi
Publications and source records attributed to A Funakoshi.
Apoptosis in the pancreas of genetically diabetic rats with a disrupted cholecystokinin (CCK-A) receptor gene.
In a previous study, we reported that the pancreatic wet weight in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, cholecystokinin-A (CCK-A) receptor-defective because of a congenital gene abnormality, was significantly lower than in control rats (Long-Evans Tokushima Otsuka; LETO) from 3 weeks of age. In this study we examined apoptosis of pancreatic acinar cells in OLETF rats at 5 to 6 weeks of age in comparison with that in LETO rats. We present here direct morphologic evidence of apoptosis in OLETF rats, using a 3'-OH nick end-labeling method for detecting cells with DNA strand breaks and electron microscopy. Nick end-labeling revealed a small number of positively labeled acinar cells in OLETF rats. On electron microscopic examination, small numbers of apoptotic cells were seen in the lobules in OLETF rats but not in LETO rats. These results suggest that apoptosis plays an important role in the destruction of acinar cells of OLETF rats and induces atrophy of the pancreas.
Animals↗
Retardation of pancreatic regeneration after partial pancreatectomy in a strain of rats without CCK-A receptor gene expression.
This study extends a recent observation that Otsuka Long-Evans Tokushima Fatty (OLETF) rats show no expression of the cholecystokinin (CCK)-A receptor gene in the pancreas because of a genetic abnormality. We compared the changes in pancreatic regeneration in terms of wet weight and protein and DNA contents after partial pancreatectomy (30% resection) in OLETF and control (Long-Evans Tokushima Otsuka: LETO) rats and examined whether the CCK-B receptor has a role in pancreatic regeneration after pancreatectomy. The pancreatic wet weight increased significantly with age in both OLETF and LETO rats regardless of surgical procedure, but the increase with respect to time was significantly less in OLETF than in LETO rats. The protein and DNA concentrations in the pancreas (mg/g wet tissue) were comparable for both strains after sham operation. However, they were significantly lower than pancreatectomy in OLETF rats compared to those after sham operation, whereas they were comparable in LETO rats regardless of surgical procedure. The ratio of protein content/DNA content (cell size) was significantly lower in OLETF than LETO rats under all conditions. CCK-B receptor gene expression was not enhanced after pancreatectomy. In conclusion, the CCK-A receptor is not an absolute requirement for pancreatic normal growth but is important for pancreatic regeneration.
Animals↗
Stimulatory effect of synthetic luminal cholecystokinin releasing factor (LCRF) fragment (1-35) on pancreatic exocrine secretion in conscious rats.
The effects of a synthetic putative luminal cholecystokinin (CCK) releasing factor (LCRF) fragment (1-35) on pancreatic exocrine secretion were examined in conscious Wistar rats and a mutant strain of rats lacking the CCK-A receptor. Intraduodenal injection of graded doses of the LCRF fragment induced biphasic responses in Wistar rats. The injection of 0.1 microgram of the LCRF fragment produced a maximal response, while 1 microgram produced a lower response. No significant effect was observed in rats lacking the CCK-A receptor. The synthetic LCRF fragment stimulated pancreatic secretion via CCK-A receptors in conscious rats.
Amino Acid Sequence↗
Regulation of cholecystokinin release and transcription in a rat without gene expression of cholecystokinin-A receptor.
An Otsuka Long-Evans Tokushima Fatty (OLETF) rat does not possess cholecystokinin (CKK)-A receptor gene expression because of a genetic abnormality. We examined the CCK release and its transcription in OLETF rats in comparison with control (Long-Evans-Tokushima-LETO) rats. Animals at 5-6 and 24-25 weeks of age were used. The level of CCK mRNA and CCK concentration in the small intestinal mucosa, and the level of CCK-A receptor mRNA in the pancreas were examined. To examine CCK release, rats were prepared with external bile and pancreatic fistulae. The basal plasma levels of CCK and those at 2 h after bile-pancreatic juice diversion were measured by radioimmunoassay. The levels of CCK mRNA, and tissue CCK concentration increased significantly with age in both strains, but the values in OLETF rats were significantly lower than those in LETO rats. The CCK-A receptor mRNA level also increased with age in LETO rats. The plasma CCK concentration was significantly increased by bile-pancreatic juice diversion regardless of age and strain; however, the level of plasma CCK in OLETF rats at 24-25 weeks of age was significantly lower than that of LETO rats. It is suggested that the long-term defect of CCK-A receptor may decrease CCK release and transcription.
Animals↗
Decrease in exploratory behavior in naturally occurring cholecystokinin (CCK)-A receptor gene knockout rats.
We recently found a specific strain of rats (Otsuka Long Evans Tokushima Fatty; OLETF rats) lacking cholecystokinin (CCK)-A receptor because of a genetic abnormality. Since CCK is an abundant neurotransmitter peptide in the brain, we examined whether these animals exhibit any behavioral abnormalities by conducting open-field tests. OLETF rats showed hypolocomotor activity and a decrease in the incidence of rearing in open-field tests. CCK release from the synaptosomes, and levels of CCK and CCK-B receptor mRNAs were the same as those observed in normal rats. It is suggested that the decreased exploration in OLETF rats may be due to the lack of CCK-A receptor.
Animals↗
Pancreastatin-like immunoreactivity in globular dystrophic neurites of senile plaques in brains of patients with Alzheimer's disease.
The immunohistochemical localization of pancreastatin (PST) was examined in brains of Alzheimer's disease (AD) and control cases using three different antisera to PST, and was compared with the staining for chromogranin A (CgA), the precursor of PST. In control brains, CgA-like immunoreactivity was observed in the cytoplasm and fibers of certain neuronal populations, which were not immunostained with any of the PST antisera. In AD brains, dystrophic neurites of globular shape located in senile plaques were immunostained with each of the PST antisera, as well as with the CgA antibody. PST-positive and CgA-positive dystrophic neurites showed similar profiles. The present study indicates that CgA is probably cleaved to produce PST in some globular dystrophic neurites in senile plaques.
Aged↗
Analysis of Ki-ras codon 12 mutations in the duodenal juice of patients with pancreatic cancer.
BACKGROUND & AIMS: Point mutations of the Ki-ras gene at codon 12 have been frequently identified in pure pancreatic juice of patients with pancreatic cancer in studies examining pancreatic cancer tissues. The aim of this study was to examine mutations of the Ki-ras codon 12 in the duodenal juice collected from patients with various pancreatic disorders. METHODS: The duodenal juice was collected through a Dreiling tube installed in the duodenum during a secretin test. Analysis of the Ki-ras mutations was performed using the enriched polymerase chain reaction--single-strand conformation polymorphism technique. RESULTS: Point mutations were detected in 12 of 19 patients with pancreatic cancer; of the 12 patients, 10 had ductal tubular adenocarcinoma and 2 intraductal papillary adenocarcinoma. Mutational patterns included GAT (n = 4), GTT (n = 3), CGT (n = 1), and double mutations of GTT and GAT (n = 3) and GAT and CGT (n = 1). In 41 patients with benign pancreatic disorders, a point mutation was detected in only 1 patient with chronic pancreatitis. CONCLUSIONS: Analysis of the Ki-ras codon 12 mutations in the duodenal juice is useful in the diagnosis of pancreatic cancer.
Base Sequence↗
Pancreatic endocrine dysfunction in rats not expressing the cholecystokinin-A receptor.
Cholecystokinin (CCK) has been suggested to modulate insulin output. We have shown that Otsuka Long-Evans Tokushima Fatty (OLETF) rats show little or no expression of the CCK-A receptor gene in the pancreas. We examined whether the CCK-A and CCK-B receptor genes are expressed in the islets and the role of CCK-A receptor in insulin secretion. Gene expressions of CCK receptors were determined by the reverse-transcriptase polymerase chain reaction (RT-PCR) followed by Southern blot hybridization and Northern transfer analysis using LETO rats as controls. Pancreatic endocrine function was examined in perfusion (exogenous CCK stimulation) and meal ingestion (endogenous CCK stimulation) studies. CCK-A receptor mRNA was detected in the islets of LETO rats but not OLETF rats. Expression of the CCK-B receptor gene was detected in both strains by RT-PCR. Insulin secretion was impaired in OLETF rats, but the insulin contents of OLETF and LETO rats were not different. No abnormalities were detected histologically in either strain. These results suggest that the occurrence of pancreatic endocrine dysfunction in OLETF rats may be due to a defect in expression of the CCK-A receptor gene, not to insulin deficiency.
Animals↗
Neurohormonal regulation of pancreatic exocrine function in rats without gene expression of the cholecystokinin-A receptor.
Otsuka Long-Evans Tokushima Fatty (OLETF) rats revealed no or reduced expression of the cholecystokinin (CCK)-A receptor gene in the pancreas and that the pancreas of this strain of rats did not respond to CCK stimulation. We examined whether the pancreatic responses to hormonal and neural stimulation except for CCK in OLETF rats were maintained. The pancreatic responses of conscious OLETF rats to various stimuli were examined in vivo and compared with those of control (Long-Evans Tokushima; LETO) rats. Moreover, the levels of expression of CCK-A and -B receptor genes in the small intestine were examined. Pancreatic responses to intravenous injection of secretin and acetylcholine and to intracerebroventricular administration of thyrotropin-releasing hormone were comparable in OLETF and LETO rats. However, responses to intravenous injection of neuromedin C, to intraduodenal injection of capsaicin, and to intragastric injection of a liquid meal were impaired in OLETF rats. CCK-A receptor mRNA was not expressed in the small intestine of OLETF rats but was in LETO rats. The pancreatic responses to various stimuli in OLETF rats were well conserved except for the involvement of CCK-A receptor function. OLETF rats are confirmed as a new experimental model deficient in CCK-A receptor gene expression and represent a useful tool for studying the physiological role of these in vivo.
Acetylcholine↗
Role of cholecystokinin (CCK)-A receptor for pancreatic growth after weaning: a study in a new rat model without gene expression of the CCK-A receptor.
This work extends a recent observation that Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which have been established as an animal model of non-insulin-dependent diabetes mellitus, show no expression of the cholecystokinin (CCK)-A receptor gene in the pancreas. The CCK-A receptor is known to be involved in regulating pancreatic exocrine function and growth. We examined the growth of the pancreas in terms of wet weight, enzyme compositions, and protein and DNA contents at 5-6 and 24-25 weeks of age in OLETF rats and control (Long-Evans Tokushima; LETO) rats. The pancreatic wet weight increased significantly with age in both OLETF and LETO rats but was significantly lower in OLETF rats than in LETO rats. The total DNA contents in the whole pancreas (cell numbers) were comparable for both strains and increased significantly with age. However, the ratio of protein content to DNA content (the cell size) significantly increased with age in LETO rats, with no increase in OLETF rats. The changes in chymotrypsin, amylase, and insulin with respect to age were in the same direction in both strains: a decrease or no change in total and/or cellular contents of chymotrypsin and insulin and increases in amylase. These results suggest that the CCK-A receptor plays some role in the increase in cell size associated with normal growth of the pancreas from 5 to 25 weeks of age (after weaning).
Aging↗
Regulation of pancreatic exocrine function in Otsuka Long-Evans Tokushima Fatty (OLETF) rats without gene expression of cholecystokinin-A receptor.
This work extends a recent observation that Otsuka Long-Evans Tokushima Fatty (OLETF) rats show a congenital defect of the cholecystokinin (CCK)-A receptor gene. Expression of CCK-A receptor mRNA in the pancreas, small intestine and brain were not detected in OLETF rats by the reverse transcriptase polymerase chain reaction. In vitro studies showed that the maximal effective concentrations of neuromedin C, acetylcholine and secretin for stimulation of amylase secretion were comparable in both strains, but that CCK-stimulated amylase secretion was observed only in Long-Evans Tokushima Otsuka (LETO) rats. Intracellular cytosolic Ca2+ movement stimulated by acetylcholine and neuromedin C was similar in both strains. In vivo studies showed that the pancreatic secretions in response to secretin and acetylcholine were not impaired in OLETF rats. However, protein responses to neuromedin C and 2-deoxy-D-glucose were impaired in OLETF rats. The findings suggest that pancreatic exocrine functions in OLETF rats are regulated by all neural and peptidergic agents except CCK.
Acetylcholine↗
[Cholecystokinin and cholecystokinin receptor].
Cholecystokinin (CCK) act as hormones and neuropeptides on central and peripheral CCK receptors. The application of modern molecular biological techniques has identified two CCK receptors, CCK-A receptor (CCKAR) and CCK-B/gastrin receptor (CCKBR). The genes of CCKAR and CCKBR consist of five exons interrupted by four introns. We have reported that OLETF rats, which have been established as an animal model of NIDDM, revealed no expression of CCKAR gene (a naturally occurring CCKAR gene knockout rat). Pancreatic exocrine functions in OLETF rats are regulated by all neural and peptidergic agents except CCK. Therefore, we have proposed that OLETF rats may be a useful experimental model for examining the biological functions of the CCKAR.
Amino Acid Sequence↗
Somatostatin inhibits pancreatic exocrine secretion centrally via sympathetic nerves in conscious rats.
Somatostatin is known to be a potent inhibitor of pancreatic exocrine secretion, but the mechanism of its effect is not fully understood. The mechanism of the inhibition by centrally administered somatostatin was examined in conscious rats. Rats were prepared with cannulae draining bile and pancreatic juice separately, and with a duodenal cannula, an extrajugular vein cannula and a cerebroventricular cannula. Somatostatin was injected into the left lateral ventricle, and the inhibitory mechanism was examined using vagotomized rats and various drugs that affect sympathetic neurons. Intracerebroventricular administration of somatostatin significantly inhibited pancreatic exocrine secretion stimulated by bile-pancreatic juice diversion. The inhibitory effect was not abolished by vagotomy, pretreatment with propranolol, but was abolished by pretreatment with hexamethonium or phentolamine. The plasma level of somatostatin after its intracerebroventricular administration increased 3-fold, but its intravenous infusion at a rate giving a similar plasma somatostatin level to that produced by its intracerebroventricular injection, had no significant effect on pancreatic secretion. These results suggest that somatostatin inhibits pancreatic exocrine secretion centrally via sympathetic efferent nerves and that alpha-adrenergic receptors have an important role in its inhibitory action.
Animals↗
Impaired release of cholecystokinin (CCK) from synaptosomes in old rats.
Cholecystokinin (CCK) is an abundant neurotransmitter peptide in the brain. CCK release from synaptosomes obtained from the cerebral cortex, the level of CCK mRNA and the tissue concentration of CCK were examined in young and old rats. CCK release stimulated by KCl was attenuated in old rats but that stimulated by calcium ionophore was comparable in animals at both ages. The CCK mRNA level in the cerebral cortex was decreased significantly in old rats despite the significant increase in CCK content. These results suggested that aging impaired CCK release, resulting in tissue accumulation and a decrease in the synthesis of CCK (the level of CCK mRNA).
Age Factors↗
The amelioration of hyperglycemia in streptozotocin-induced diabetic rats after the intraportal transplantation of an insufficient number of islets by nicotinamide treatment.
The purpose of the present study was to determine whether or not hyperglycemia in streptozotocin (STZ)-induced diabetic rats after the intraportal transplantation of an insufficient number of isogenic islets can be ameliorated by nicotinamide treatment. WKA/Qdj (RT 1u) rats were used both as donors and recipients. Islets were isolated by the collagenase technique. A total of 350 islets was transplanted into the liver via the portal vein of the STZ-induced diabetic rats. Either nicotinamide (NA, 0.5 g/kg) or a vehicle (saline) was administered ip once a day for 60 days after transplantation. All the diabetic rats without islet transplantation remained hyperglycemic irrespective of the NA treatment. All the recipients (n = 12) bearing the islet grafts and treated with saline remained hyperglycemic (> 400 mg/dl) at 60 days after transplantation. In marked contrast, all the recipients (n = 18) with islet grafts and treated with NA became normoglycemic (< 200 mg/dl) at 16.2 +/- 7.1 days (mean +/- SD) after transplantation. Morphologically, islets were easily found in the liver of the recipients. Aldehyde-fuchsin stain revealed that the beta cells in the islet grafts of the NA treated recipients were well granulated, whereas those treated with saline were degranulated. The insulin content of the liver bearing the grafts treated with either NA or saline was 116.3 +/- 26.0 micrograms/liver (n = 4) or 5.7 +/- 2.2 micrograms (n = 4), respectively, while that of 350 donor islets was 29.4 +/- 2.5 micrograms (n = 5). The insulin content of the pancreas in the NA- or saline-treated recipients was 27.3 +/- 10.6 micrograms/pancreas (n = 4) or 2.7 +/- 1.2 micrograms (n = 4), respectively, while those of the pancreas from the diabetic rats without transplantation was 1.9 +/- 0.7 micrograms (n = 4) or 1.6 +/- 0.8 micrograms (n = 5), respectively. These findings clearly demonstrate that the hyperglycemia in the STZ-diabetic recipients after transplantation of an insufficient number of islets can be ameliorated while, in addition, the islet mass in the liver as well as the endogenous pancreas both increase in size with nicotinamide treatment.
Animals↗
Gene structure of rat cholecystokinin type-A receptor.
Little is known about the gene structure and mRNA expression of cholecystokinin type-A(CCKA) receptor in animals or in human. By screening an EMBL phage library containing partially digested Long-Evans rat DNA, we isolated 7 genomic clones covering a continuous 27 kb region over which a rat CCKA receptor gene spanned. The gene is approximately 10 kb in length containing the entire coding region of the rat CCKA receptor cDNA and consists of five exons interrupted by four introns. The expected sizes of the transcripts from the initiation sites were consistent with the results of northern blot analyses.
Amino Acid Sequence↗