PubMed Health⌕ Search

Biomedical subjects

Satoru Naruse

Publications and source records attributed to Satoru Naruse.

28 records · Page 2Linked to original sources

Molecular pathophysiology of pancreatitis.

Though hereditary pancreatitis is a very rare form of pancreatitis, the discovery of the gene for hereditary pancreatitis provides important implications for pancreatitis in general. A premature activation of trypsinogen is likely to occur not infrequently in our daily life as the onset of the disease is well advanced before a drinking habit starts. It probably goes unnoticed in normal individuals because normal inhibitory mechanisms described above prevent the development of pancreatitis. Any disorders or agents that cause abnormalities in this natural protective mechanism can cause pancreatitis. Genotype-phenotype analyses of CFTR mutations in chronic pancreatitis are necessary to establish the relationship between CFTR and this disease. It remains to be shown how a reduction of functional CFTR causes chronic pancreatitis.

Acute Disease↗

A molecular mechanism for aberrant CFTR-dependent HCO(3)(-) transport in cystic fibrosis.

Aberrant HCO(3)(-) transport is a hallmark of cystic fibrosis (CF) and is associated with aberrant Cl(-)-dependent HCO(3)(-) transport by the cystic fibrosis transmembrane conductance regulator (CFTR). We show here that HCO(3)(-) current by CFTR cannot account for CFTR-activated HCO(3)(-) transport and that CFTR does not activate AE1-AE4. In contrast, CFTR markedly activates Cl(-) and OH(-)/HCO(3)(-) transport by members of the SLC26 family DRA, SLC26A6 and pendrin. Most notably, the SLC26s are electrogenic transporters with isoform-specific stoichiometries. DRA activity occurred at a Cl(-)/HCO(3)(-) ratio > or =2. SLC26A6 activity is voltage regulated and occurred at HCO(3)(-)/Cl(-) > or =2. The physiological significance of these findings is demonstrated by interaction of CFTR and DRA in the mouse pancreas and an altered activation of DRA by the R117H and G551D mutants of CFTR. These findings provide a molecular mechanism for epithelial HCO(3)(-) transport (one SLC26 transporter-electrogenic transport; two SLC26 transporters with opposite stoichiometry in the same membrane domain-electroneutral transport), the CF-associated aberrant HCO(3)(-) transport, and reveal a new function of CFTR with clinical implications for CF and congenital chloride diarrhea.

Amino Acid Sequence↗

Distribution of aquaporin 1 in the rat pancreatic duct system examined with light- and electron-microscopic immunohistochemistry.

The pancreatic duct is the major site for the secretion of pancreatic fluid, but the pathway of water transport in this system is not known. Recently, intense signal for mRNA of aquaporin 1 (AQP1) water channels was detected in isolated rat interlobular ducts. Therefore, we performed light- and electron-microscopic (EM) immunohistochemistry for AQP1 in the rat pancreatic ducts. AQP1 immunoproducts were not observed in the acinar cells, centroacinar cells or intercalated ducts. In the smaller intralobular ducts less than 10 microm in diameter (the lumen plus duct cells), most cells were immunonegative. AQP1-positive cells appeared in intralobular ducts 10-15 microm in diameter. In small and medium-sized interlobular ducts 15-70 microm in diameter surrounded by periductal connective tissue 2-40 microm thick, most cells were AQP1 positive with various degrees of immunoreactivity. In the larger interlobular ducts, the expression of AQP1 was variable, ranging from immunopositive to negative. In the main pancreatic duct, most cells were negative for AQP1. EM immunohistochemistry of the intralobular and small interlobular ductal epithelial cells showed that the AQP1 immunoproducts were more abundant in the basolateral membrane than in the apical membrane, though they were present in both membranes. In the medium-sized interlobular ducts, AQP1 immunoproducts were distributed densely along the apical, lateral interdigitation and basal membrane of the epithelial cells. In the various sizes of interlobular ducts, immunoproducts were associated not only with the plasma membrane, but also with the caveolae and vesicle-like structures. Secretin did not induce any significant difference in AQP1 expression and cellular and subcellular localization. These results indicate that the expression and subcellular localization of AQP1 vary considerably depending on the duct size, which may reflect water transport characteristics in the different divisions of the pancreatic duct system.

Animals↗

Clinical evidence of pathogenesis in chronic pancreatitis.

Chronic pancreatitis is a continuing inflammatory disease characterized by irreversible morphological change and, typically, by pain and permanent impairment of function. The pathogenesis of pancreatitis, either acute or chronic, is still controversial. There have been no widely accepted concepts to provide a reasonable explanation linking the known etiological factors and the pathophysiological aspects of the disease. Alcohol is undoubtedly the major etiological factor in most countries, and the relative importance of alcohol as a cause of chronic pancreatitis ranges from 40% to 90% in various countries. As fewer than 10% of alcoholics develop chronic pancreatitis, other nutritional or genetic influences are likely to be involved in the pathogenesis of alcoholic pancreatitis. Accessory pancreas incidentally found in patients with chronic alcoholic pancreatitis does not always have the pathological findings seen in the main pancreas. Integrity of the pancreatic duct seems to be another important factor for chronic alcoholic pancreatitis. Gene mutations of the cystic fibrosis transmembrane conductance regulator (CFTR), cationic trypsinogen, and pancreatic secretory trypsin inhibitor have been investigated in idiopathic chronic pancreatitis. Molecular and cell biology research during the past few years has elucidated pathophysiological factors that are involved in the pathogenesis of chronic pancreatitis, but cannot demonstrate a common pathway between etiological factors and the pathogenesis or development of the disease.

Chronic Disease↗

Feedback regulation of pancreatic secretion by peptide YY.

The present status of our understanding of the feedback regulation of pancreatic secretion by peptide YY (PYY) released from the distal intestine is reviewed. Exocrine pancreatic secretion is primarily controlled by the cephalic (the vagus nerve), gastric (acid and pepsin secretion, and nutrients delivered into the duodenum by gastric emptying), and intestinal (secretin and CCK) mechanisms. PYY acts on the multiple sites in the brain and gut, and inhibits pancreatic secretion by regulating these primary control mechanisms. The involvement of Y(1) and Y(2) receptors has been suggested in the regulation of pancreatic secretion. However, it remains to be studied which site of action or receptor subtype is physiologically most important for this regulation.

Animals↗

Cystic fibrosis and related diseases of the pancreas.

The discovery of the gene for cystic fibrosis (CF), the cystic fibrosis transmembrane conductance regulator (CFTR), brought about a new era in the study of this disease. Identification of the molecular target has yielded a flood of data that add to our understanding of the pathogenesis, diagnosis and treatment of CF. The CFTR protein is a cAMP-regulated Cl(-) channel with multiple functions in epithelial cells. In the exocrine pancreas the CFTR plays a key role in the apical Cl(-), HCO(3)(-), and water transport in duct cells. The severe loss of functions, caused by mutations of the CFTR gene, leads to pathological lesions of the pancreas. Over 1200 CFTR mutations and polymorphisms have been identified and their diversity may explain the high level of heterogeneity in the CF phenotype. Mutation analyses of the CFTR gene have revealed a spectrum of CFTR-related diseases that do not fit the classical CF picture but are associated with dysfunction of CFTR, such as chronic pancreatitis.

Chronic Disease↗

Motilin regulates interdigestive gastric blood flow in dogs.

BACKGROUND & AIMS: Gastric blood flow exhibits cyclical increases in phase with the interdigestive contractions and secretion of the stomach in dogs. The aim of this study is to clarify the regulatory role of motilin in interdigestive gastric blood flow in dogs. METHODS: Blood flow of the left gastric (LGA) and superior mesenteric (SMA) arteries were measured by ultrasound transit-time blood-flow meters in 5 conscious dogs. Motilin was infused intravenously with or without Phe-cyclo[Lys-Tyr(3-tBu)-betaAla-]. trifluoroacetate (GM-109; motilin antagonist), granisetron (5-HT3 antagonist), atropine, hexamethonium (C6), phenoxybenzamine, propranolol, or cimetidine. RESULTS: Motilin (12.5, 25, 50, and 100 pmol x kg(-1) x h(-1)) induced LGA blood-flow responses, consisting of a sustained increase and a rapid phasic change coupled with a contraction, without affecting the blood pressure, heart rate, and SMA blood flow. GM-109 completely abolished the LGA, motility, and secretory responses to motilin (100 pmol x kg(-1) x h(-1)). Atropine abolished motilin-induced gastric contractions, secretion, and phasic changes of LGA blood flow but failed to affect the sustained flow increase. However, atropine partially inhibited the LGA responses to lower doses of motilin. The LGA flow responses to motilin were not inhibited by granisetron, C6, alpha-adrenergic, beta-adrenergic, or H2 blockers. Motilin induced significantly larger gastric vasodilatation than the equivalent doses of VIP. CONCLUSIONS: Motilin has a potent and selective gastric vasodilator effect, which appears to be mediated by both cholinergic and noncholinergic mechanisms. Motilin plays an important role in the regulation of interdigestive gastric blood flow in dogs.

Adrenergic Antagonists↗

Aquaporins in rat pancreatic interlobular ducts.

The aquaporin (AQP) family of water channels is distributed ubiquitously in many epithelia and plays a fundamental role in transmembrane water transport. The aim of this study is to identify the water transport pathway in pancreatic duct cells where most of the HCO-rich fluid originates. Using digital videomicroscopy, we measured the osmotic water permeability (P(f)) of pancreatic duct epithelium by exposing isolated rat interlobular ducts to the hypotonic solution (145 mosM). To identify mRNA and protein of AQPs expressed in duct cells, we conducted RT-PCR analysis and immunohistochemistry of the isolated duct and pancreas. The calculated P(f) (160-230 microm/s) of the isolated ducts was significantly reduced to 16-35 microm/s by 80-90% with either basolateral or luminal applications of HgCl(2). Fluid secretion evoked by secretin was almost completely abolished by a basolateral or luminal application of HgCl(2). A large amount of AQP1 and small amounts of AQP5 transcripts were detected in the isolated duct cells by RT-PCR. AQP1, but not AQP5, immunoreactivity was present in both luminal and basolateral membranes of the interlobular duct cells. Mercury-sensitive water channels are present in both luminal and basolateral membranes of rat pancreatic ducts. AQP1 of the known AQPs appears to be the main water pathway in interlobular ducts.

Animals↗

Pancreatic stone protein of pancreatic calculi in chronic calcified pancreatitis in man.

CONTEXT: The role of protein components of pancreatic secretions has been controversial in pancreatic stone formation. OBJECTIVE: To study the lithogenic role of pancreatic stone protein and lactoferrin in stone formation in chronic pancreatitis. PATIENTS: Pancreatic stones were collected from 13 patients with alcoholic (n=6) and nonalcoholic (n=7) chronic calcified pancreatitis. MAIN OUTCOME MEASURES: Pancreatic stone extracts were analyzed for pancreatic stone protein and lactoferrin using enzyme immunoassay. The localization of pancreatic stone protein immunoreactivity in the stone was observed using immunogold staining and scanning electron microscopy. RESULTS: Immunoreactivities for pancreatic stone protein were detected in the stones from all 13 patients with chronic calcified pancreatitis and for lactoferrin in the stones from five of the 13 patients. Pancreatic stone protein immunoreactivity distributed diffusely from the center to the periphery of the pancreatic stones. CONCLUSIONS: Involvement of pancreatic stone protein seems to be constant from the initial step of the stone formation to subsequent steps of the stone growth. However, pancreatic stone protein is only one of the precipitating proteins in pancreatic secretions such as lactoferrin, trypsinogen, etc.

Adult↗