Effect of herpesvirus infection on pancreatic duct cell secretion

AIM： To examine the effect of acute infection caused by herpesvirus （pseudorabies virus, PRV） on pancreatic ductal secretion. METHODS： The virulent Ba-DupGreen （BDG） and non- virulent Ka-RREp01acgfp （KEG） genetically modified strains of PRV were used in this study and both of them contain the gene for green fluorescent protein （GFP）. Small intra/ interlobular ducts were infected with BDG virus （10^7 PFU/mL for 6 h） or with KEG virus （10^10 PFU/mL for 6 h）, while non-infected ducts were incubated only with the culture media. The ducts were then cultured for a further 18 h. The rate of HCO3 secretion [base efflux -λ（B）] was determined from the buffering capacity of the cells and the initial rate of intracellular acidification （1） after sudden blockage of basolateral base loaders with dihydro-4,4,- diisothiocyanatostilbene-2,2,-disulfonic acid （500 μmol/L） and amiloride （200 μmol/L）, and （2） after alkali loading the ducts by exposure to NH4Cl. All the experiments were performed in HCO3-buffered Ringer solution at 37 ℃ （n = 5 ducts for each experimental condition）. Viral structural proteins were visualized by immunohistochemistry. Virallyencoded GFP and immunofluorescence signals were recorded by a confocal laser scanning microscope.RESULTS： The BDG virus infected the majority of accessible cells of the duct as judged by the appearance of GFP and viral anUgens in the ductal cells. KEG virus caused a similarly high efficiency of infection. After blockage of basolateral base loaders, BDG infection significantly elevated -λB-） 24 h after the infection, compared to the non-infected group. However, KEG infection did not modify -λB-）. After alkali loading the ducts, -λB-） was significantly elevated in the BDG group compared to the control group 24 h after the infection. As we found with the inhibitor stop method, no change was observed in the group KEG compared to the non-infected group. CONCLUSION： Incubation with the BDG or KEG strains of PRV results in an effective infection of ductal epithelial cells. The BDG strain of PRV, which is able to initiate a lytic viral cycle, stimulates HCO3 secretion in guinea pig pancreatic duct by about fourto fivefold, 24 h after the infection. However, the KEG strain of PRV, which can infect, but fails to replicate, has no effect on HCO3 secretion. We suggest that this response of pancreatic ducts to virulent PRV infection may represent a defense mechanism against invasive pathogens to avoid pancreatic injury.

Insulin is necessary for the hypertrophic effect of cholecystokinin-octapeptide following acute necrotizing experimental pancreatitis

AIM:In previous experiments we have demonstrated that by administering low doses of cholecystokinin-octapeptide (CCK-8),the process of regeneration following L-arginine (Arg)-induced pancreatitis is accelerated.In rats that were also diabetic(induced by streptozotocin,STZ),pancreatic regeneration was not observed.The aim of this study was to deduce whether the administration of exogenous insulin could in fact restore the hypertrophic effect of CCK-8 in diabetic-pancreatitic rats. METHODS:Male Wistar rats were used for the experiments. Diabetes mellitus was induced by administering 60mg/kg body mass of STZ intraperitoneally(i.p.),then,on d 8, pancreatitis was induced by 200mg/100 g body mass Arg i.p.twice at an interval of 1 h.The animals were injected subcutaneously twice daily(at 7 a.m.and 7 p.m.)with 1 μg/kg of CCK-8 and/or 2 IU mixed insulin(300g/L short- action and 700g/L intermediate-action insulin) for 14 d after pancreatitis induction.Following this the animals were killed and the serum amylase,glucose and insulin levels as well as the plasma glucagon levels,the pancreatic mass/body mass ratio(pm/bm),the pancreatic contents of DNA,protein,amylase,lipase and trypsinogen were measured.Pancreatic tissue samples were examined by light microscopy on paraffin-embedded sections. RESULTS:In the diabetic-pancreatitic rats treatment with insulin and CCK-8 significantly elevated pw/bm and the pancreatic contents of protein,amylase and lipase vs the rats receiving only CCK-8 treatment.CCK-8 administered in combination with insulin also elevated the number of acinar cells with mitotic activities,whereas CCK-8 alone had no effect on laboratory parameters or the mitotic activities in diabetic-pancreatitic rats. CONCLUSION:Despite the hypertrophic effect of CCK-8 being absent following acute pancreatitis in diabetic-rats, the simultaneous administration of exogenous insulin restored this effect.Our results clearly demonstrate that insulin is necessary for the hypertrophic effect of low-doses of CCK-8 following acute pancreatitis.

L-arginine-induced experimental pancreatitis

Despite medical treatment,the lethality of severe acute pancreatitis is still high (20-30%).Therefore,it is very important to find good animal models to characterise the events of this severe disease.In 1984,Mizunuma et al. developed a new type of experimental necrotizing pancreatitis by intraperitoneal administration of a high dose of L-arginine in rats.This non-invasive model is highly reproducible and produces selective,dose-dependent acinar cell necrosis. Not only is this a good model to study the pathomechanisms of acute necrotizing pancreatitis,but it is also excellent to observe and influence the time course changes of the disease.By writing this review we iluminate some new aspects of cell physiology and pathology of acute necrotizing pancreatitis.Unfortunately,the reviews about acute experimental pancreatitis usually did not discuss this model. Therefore,the aim of this manuscript was to summarise the observations and address some challenges for the future in L-arginine-induced pancreatitis.