Diagnostic approach to the patient with jaundice following trauma.

BACKGROUND AND AIMS: Jaundice in trauma patients may reflect serious underlying pathology. The aim of this review was to determine the appropriate diagnostic approach to the patient with jaundice following trauma. METHODS: A MEDLINE search was performed to retrieve publications which outlined the causes of jaundice in trauma patients. RESULTS: The main causes of jaundice in trauma patients were found to be bilirubin overload caused by breakdown of transfused- and extravasated blood and hepatic dysfunction caused by sepsis, infections, initial shock and systemic hypotension. Bile duct injury or drug induced liver injury are rare. Liver function tests are often uninformative but commonly show a cholestatic pattern. Ultrasound, CT or ERCP are the diagnostic imaging methods most widely used. Abdominal ultrasound and CT may reveal specific organ injuries, bile duct dilatation, intraabdominal fluid collections, hematomas or acalculus cholecystitis. ERCP is often diagnostic and permits a therapeutic intervention when a bile duct injury is present. CONCLUSIONS: The primary aim of the diagnostic approach should be to identify all cases of bile duct injury or obstruction. Sepsis and infections should be actively looked for. The number of blood transfusions must be calculated. Ultrasound, CT or ERCP are the diagnostic imaging methods most widely used.

Aetiology and prognostic implication of severe jaundice in surgical trauma patients.

BACKGROUND: Pronounced postoperative jaundice occurs not infrequently in trauma patients. The aim of this study was to elucidate the implication of early, pronounced jaundice (serum-bilirubin >100 micromol x l(-1)) for 30-day survival of such patients. METHODS: From 1995 through 2001, 53 surgical trauma patients developing pronounced postoperative jaundice were identified. Nine were excluded from the study because of major hepatobiliary injury or pre-existing liver disease. The clinical course and laboratory chemistry profiles of the remaining 44 patients were analysed. RESULTS: Thirty-one patients survived and 13 died within 30 days of trauma. Non-survivors had higher age, higher injury severity score (ISS) and lower probability of survival (PS) (P < 0.05) than survivors. ISS averaged 34 in survivors and 45 in non-survivors. Survivors and non-survivors received a mean of 46 (range 10-97) and 55 units of blood (range 11-128), respectively (P = 0.366). Systemic hypotension, local infections and sepsis were common in both groups. Bilirubin levels peaked around the 11th day in survivors (median 189 micromol x l(-1)). In non-survivors, serum bilirubin values rose progressively, reaching maximum levels at time of death (median 231 micromol x l(-1)). These patients died in a setting of sepsis and multiple organ failure. CONCLUSION: Large endogenous production of bilirubin because of rapid breakdown of transfused and extravasated blood can cause pronounced jaundice in multitransfused trauma patients. In such patients, serum bilirubin rising >100 micromol x l(-1) does not by itself signal poor outcome. However, progressive pronounced jaundice outlasting the trauma incident by 10-12 days portends fatal outcome for the patient.

Cholestatic effect of large bilirubin loads and cholestasis protection conferred by cholic acid co-infusion: a molecular and ultrastructural study.

BACKGROUND: Large intravenous bilirubin loads block biliary phospholipid secretion, produce canalicular membrane lesions and cause canalicular cholestasis. Cholic acid co-infusion forestalls these untoward effects. The aim of this study was first to determine whether bilirubin overload causes cholestasis through reducing the activity or the hepatic expression of the bile salt export pump (bsep) or Na-taurocholate co-transporting polypeptide (ntcp) and, secondly, whether cholic acid co-infusion forestalls cholestasis by upregulating bsep, ntcp or phosphoglycoprotein 3 (pgp3) expressions or activities. A further aim was to determine whether large bilirubin infusions also produce ultrastructural changes inside hepatocytes. METHODS: The effects of intravenous infusion of 2 g bilirubin over 150 min on hepatic expression of bsep, ntcp and pgp3 were studied in bile acid-depleted and cholic acid co-infused pigs, and related to canalicular bile acid transport and bile secretion. Effects on hepatocyte ultrastructural morphology were analysed by electron microscopy. RESULTS: Bilirubin-induced cholestasis reflected marked diminution of bsep and pgp3 transport activities and not reduced hepatic expression of these transporters. Hepatocyte ultrastructural abnormalities were predominantly confined to the hepatocyte canalicular membrane in cholestatic livers. Cholic acid co-infusion with bilirubin conferred complete cholestasis protection through enhancing pgp3 and bsep transporter activities and not through upregulating their expression. Bilirubin infusion did not change ntcp expression. CONCLUSION: Bilirubin-induced cholestasis is due to markedly impaired activity of the membrane-embedded bsep transporter consequent upon ultrastructural injury to the canalicular membrane. Cholic acid co-infusion with bilirubin enhances bsep and pgp3 activities and confers protection against canalicular membrane injury and bilirubin-induced cholestasis.

Intravenous bilirubin, dibromosulfophthalein, and bromosulfophthalein infusions uncouple biliary phospholipid and cholesterol secretion from bile acid secretion by inhibiting hepatic phosphoglycoprotein-3 activity in pigs.

BACKGROUND: Biliary secretion of organic anions disturbs the proportional relationship normally pertaining between biliary lipid and bile acid secretion. The mechanism causing this uncoupling of biliary lipid from bile acid secretion is incompletely understood. Impaired micellization of membrane lipids by bile due to biliary contamination with organic anions or lowering of biliary bile acid concentration by enhanced bile acid-independent bile flow has been proposed as causative factors. Recently, we found that hepatic phosphoglycoprotein 3 (pgp3) activity was reduced in pigs during bilirubin-induced uncoupling of biliary lipid from bile acid secretion. Pgp3 is the phosphatidylcholine flippase in the canalicular membrane sustaining biliary phospholipid secretion in pigs. This investigation was undertaken to examine whether bilirubin, dibromosulfophthalein, and bromosulfophthalein uncouple biliary lipid from bile acid secretion by the same mechanism. METHODS/RESULTS: Hepatic bile was collected from 24 anesthetized pigs before and during infusion of 0.63 micromol x kg body wt(-1) x min(-1) intravenous bilirubin, dibromosulfophthalein, or bromosulfophthalein. Bile acid secretion was varied by intraportal cholic acid infusion. Hepatic pgp3 expression was measured by means of Western blot, using C219 antibody. Bilirubin > dibromosulfophthalein > bromosulfophthalein lowered biliary lipid secretion without altering hepatic pgp3 expression, increased bile acid-independent bile flow (bromosulfophthalein > dibromosulfophthalein > bilirubin), and enhanced the capacity of bile to micellize membrane lipids as assayed by means of erythrocyte lysis. Biliary bile acid concentration did not determine biliary lipid secretion. CONCLUSION: Bilirubin, dibromosulfophthalein, and bromosulfophthalein in bile uncouple biliary lipid from bile acid secretion by inhibiting hepatic pgp3 phosphatidylcholine flippase activity, putatively through diffusing into the pgp3 pore.

Effect of intravenous bilirubin infusion on biliary phospholipid secretion, hepatic P-glycoprotein expression, and biliary cytotoxicity in pigs.

BACKGROUND: Infusion of large intravenous bilirubin loads in bile acid-depleted pigs reduces P-glycoprotein-dependent biliary phospholipid secretion and increases the cytotoxicity of bile. The reasons for the diminution of biliary phospholipid secretion and the increase in biliary cytotoxicity are not known. This study was undertaken to determine whether the bilirubin-induced lowering of biliary phospholipid secretion is associated with alterations in hepatic P-glycoprotein (P-gp) expression and to determine why bilirubin infusions increase biliary cytotoxicity. METHODS: Hepatic bile was collected from bile acid-depleted pigs before and during intravenous bilirubin infusion. Hepatic P-gp expression was measured with protein blot analysis, using the P-gp-specific antibody C219. Biliary cytotoxicity was assayed against erythrocytes. The biliary phospholipid fatty acid profile was determined by means of gas chromatography. RESULTS: Bilirubin infusions lowered biliary phospholipid secretion by 69% without changing hepatic P-gp expression, suggesting that bilirubin infusions have an inhibitory effect on hepatic P-gp activity. Bilirubin infusions did not cause P-gp losses into bile. An unequivocal, proportional relationship (r2 = 0.80) pertained between cytotoxicity and the bile acid to phospholipid ratio in bile secreted before and during bilirubin infusion and in phosphatidylcholine-supplemented bile. Unconjugated bilirubin in bile did not contribute to biliary cytotoxicity. Biliary phospholipids were always phosphatidylcholine >> phosphatidylethanolamine, mainly of C16:0, 18:2 and C16:0, 18:1 fatty acid configuration. CONCLUSIONS: Intravenous bilirubin loads reduce biliary phospholipid secretion without changing hepatic P-gp expression. Bilirubin infusions increase biliary cytotoxicity by augmenting the biliary bile acid to phospholipid ratio.

Large intravenous bilirubin loads increase the cytotoxicity of bile and lower the resistance of the canalicular membrane to cytotoxic injury and cause cholestasis in pigs.

BACKGROUND: Large intravenous bilirubin loads cause loss of hepatic canalicular membrane microvilli and cholestasis. This study examines whether these untoward effects might be due to canalicular membrane injury from cytotoxic bile. METHODS: The cytotoxicity of bile was assayed against pig erythrocytes before and throughout 4.5-h intravenous infusion of 170 microg kg(-1) body weight of bilirubin in anaesthetized pigs. The capacity to generate canalicular bile flow was tested before and after bilirubin infusion by means of short-term intraportal cholic acid infusion. RESULTS: Bilirubin infusion increased the cytotoxicity of hepatic bile, reduced biliary phospholipid secretion by 90%, and caused cholestasis. Cholic acid infusion before bilirubin also increased the cytotoxicity of bile but increased bile flow and doubled biliary phospholipid output. CONCLUSION: Large intravenous bilirubin infusions increase the cytotoxicity of bile, suppress biliary phospholipid secretion, and render hepatic canalicular membrane microvilli susceptible to injury from cytotoxic bile so that cholestasis occurs.

Large intravenous loads of bilirubin photoconversion products, in contrast to bilirubin, do not cause cholestasis in bile acid-depleted pigs.

BACKGROUND: Large intravenous bilirubin infusions in bile acid-depleted pigs (BADP) destroy hepatocyte canalicular membrane microvilli (CMV) and cause cholestasis. This study examines whether bilirubin photoconversion product infusions do the same. METHODS: The effects of systemic infusion of 135 mumol.kg-1 body weight bilirubin photoconversion products on CMV density and choleretic response to intraportal bile acid infusion were studied in BADP. Furthermore, the effects of 135 mumol.kg-1 b.w. bilirubin infusion, either through an arteriovenous bilirubin photoconversion shunt device (PCD) or intravenously, were measured in PCD-connected BADP. RESULTS: Intravenous bilirubin photoconversion product infusions affected neither the CMV density nor the choleretic response to cholic acid infusion, and neither did bilirubin infusion through the PCD. In contrast, intravenous bilirubin infusion caused canalicular injury and cholestasis in four of six PCD-connected BADP. CONCLUSION: Bilirubin photoconversion products do not destroy CMV or cause cholestasis in BADP. A bilirubin photoconversion shunt device can confer cholestasis protection to bilirubin-loaded BADP.

Bile acids protect the liver against the cholestatic effect of large bilirubin loads.

BACKGROUND: This study was undertaken to elucidate why large bilirubin loads cause canalicular cholestasis and whether bile acid infusions protect against bilirubin-induced cholestasis. METHODS: The effects of bilirubin infusion on canalicular bile secretion and canalicular membrane morphology were studied in bile acid-depleted pigs (BADP), bile acid-primed pigs (BAPP), and pigs co-infused with bile acids during bilirubin loading (BACIP). RESULTS: Bilirubin caused complete cholestasis in BADP, 38% bile flow reduction in BAPP, and no effect on bile flow in BACIP. Scanning electron micrographs showed loss of 70% of canalicular microvilli in BADP, 13% loss and pathologic changes in the remaining 75% of microvilli in BAPP, and no canalicular changes in BACIP. Cholestasis was not due to hydromechanical obstruction of bile ductules or bile Ca2+ depletion. CONCLUSION: Bilirubin causes cholestasis in BADP by injuring canalicular microvilli. Intravenous glycocholate infusions fully protect the liver against bilirubin-induced cholestasis and canalicular microvillar injury.

Secretin causes H+/HCO3- secretion from pig pancreatic ductules by vacuolar-type H(+)-adenosine triphosphatase.

BACKGROUND/AIMS: Secretin stimulates pancreatic ductules to secrete HCO3- into pancreatic juice and H+ into interstitial fluid. The aim of the present study was first to examine whether ductular H+ secretion is inhibited by micromolar concentrations of bafilomycin A1, which blocks vacuolar H(+)-adenosine triphosphatase by specific action, and secondly to test for evidence of ductular Na+/HCO3- cotransport. METHODS: Ductular H+ secretion was estimated from the rate of intracellular pH recovery after acid-loading (24 mmol/L NH4Cl) microdissected pancreatic ductules from pig, mounted in a flow-through perfusion chamber on the stage of a fluorescent microscope. Intracellular pH was measured using the fluorescent pH indicator 2'7'-bis (carboxyethyl)-5,6-carboxyfluorescein and dual-wave-length excitation of fluorescence. The ducts were superfused perfused with either HCO3(-)-free HEPES-containing buffers or HCO3(-)-containing buffers. RESULTS: Secretin (10(-8) mol/L) induced a net H+ secretion of 1.87 +/- 0.23 mumol.mL cell vol-1.min-1 that was blocked by 10(-6) mol/L bafilomycin A1 and was unaffected by Na+ substitution with choline using HEPES superfusion buffers. Secretin-stimulated ductules superfused with bicarbonate-containing, Cl(-)-free buffers showed Na(+)-dependent and 4,4'-diisothiocyanostilbene-2, 2'-disulfonic acid-inhibitable alkalinization of intracellular pH. CONCLUSIONS: Secretin causes H+/HCO3- secretion from pancreatic ductules by a mechanism involving vacuolar-type H(+)-adenosine phosphatase. Pancreatic ductules also show Na+/HCO3- cotransport, which may account for a small fraction of secreted bicarbonate.

Secretin causes H+ secretion from intrahepatic bile ductules by vacuolar-type H(+)-ATPase.

Intrahepatic bile duct epithelial cells contribute to bile formation by hormone-dependently secreting HCO3- to bile and H+ to periductular fluid. The present study was undertaken to determine whether the secretin-induced H+ secretion is due to activation of a H(+)-ATPase or Na(+)-H+ exchange. H+ secretion was estimated from the rate of intracellular pH (pHi) recovery after acid loading (24 mM NH4Cl) of microdissected bile ductules from pig liver mounted in a flow-through chamber on the stage of a microscope. pHi was measured from an estimated average of 10-15 epithelial cells using the fluorescent pHi indicator 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and dual-wavelength excitation of fluorescence. The ducts were superfused with HCO3(-)-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffers. We found that secretin induced net H+ secretion of 4.53 +/- 0.7 mumol.ml cell volume-1 x min-1. This H+ secretion was blocked by 10(-6) M bafilomycin A1 but was unaffected by Na+ substitution with choline in the superfusion buffer. The experiments also showed that bafilomycin A1 did not block Na(+)-H+ exchange. The secretin-induced H+ secretion is probably caused by a vacuolar-type H(+)-ATPase and may constitute an important element of the cellular mechanisms causing secretin-dependent ductular HCO3- secretion into bile.

[Prospective comparative studies as tools for quality assurance. Important when laparoscopic techniques are introduced]. / Prospektive sammenliknende studier som kvalitetssikringsredskap. Viktig ved innføring av laparoskopiske teknikker.

During the first two years of laparoscopic surgery altogether 200 cholecystectomy and 40 appendectomy patients were included in prospective, comparative studies. The stay in hospital averaged two days after laparoscopic versus seven days after open cholecystectomy. Days away from work postoperatively averaged nine days after laparoscopic, versus 28 days after open cholecystectomy. After appendectomy, the stay in hospital was reduced from three to one day and absence from work from 14 days in the open surgery group to seven days in the laparoscopic group. Clear advantages have thus been documented in the groups with mini-invasive treatment, since only 5% experienced postoperative complications after laparoscopic treatment, as against 11% after open cholecystectomy (p < 0.02).

Introduction of laparoscopic techniques in gastrointestinal surgery: experience at a Norwegian university hospital as revealed by prospective comparative studies.

Prospective studies compared (a) laparoscopic and open cholecystectomy and (b) laparoscopic and open appendectomy. A second purpose of this study was to assess the value of laparoscopic staging of pancreatic and liver tumors. A total of 141 cholecystectomy cases were studied, comprising a laparoscopic group (n = 50), an open prospective control group (n = 50), and historical controls (n = 41). The need for postoperative analgesics was significantly reduced with the laparoscopic procedure compared with open cholecystectomy. Hospital stay was 1 (1-5) day after laparoscopic cholecystectomy versus 6 (5-28) days after open cholecystectomy. Time away from work was 9 (4-21) versus 28 (21-60) days. These differences were statistically significant (p < 0.001). Complication rates were 8% in both prospective groups. A similar comparative study of laparoscopic appendectomy versus the open technique was undertaken, with 10 patients in each prospective group. Again, hospital stay and time away from work proved shorter for laparoscopic procedures. Finally, 15 staging procedures for pancreatic and liver cancers were performed. One patient with unresectable liver metastases was spared explorative laparotomy.

Secretin stimulates bile ductules to secrete both H+ and HCO3(-)-ions.

Secretin-dependent ductular HCO3- secretion into bile may involve secretion of H+ to interstitial fluid and HCO3- to bile by the ductular epithelium. To determine whether secretin causes bile ductules to secrete H+, we have examined the effect of secretin on the elimination of an intracellular acid load from bile ductular epithelium during pharmacological blockade of Na(+)-H+ exchange and in the absence of HCO3-. Microdissected bile ductules from pigs were suspended in HCO3- free HEPES buffer and loaded with acid using an NH4Cl prepulse technique. Intracellular pH was measured using dual-wavelength excitation of BCECF fluorescence. Na(+)-H+ exchange was defined as a Na(+)-dependent and amiloride- and 5-(N,N-hexamethylene)-amiloride-sensitive efflux of H(+)-ions following acid loading. We found that secretin stimulated ductular H+ secretion independent of Na(+)-H+ exchange. Blockade of Na(+)-H+ exchange by hexamethylene-amiloride did not affect secretin-dependent ductular HCO3- choleresis in vivo. We conclude that secretin stimulates bile ductules to secrete H(+)-ions to interstitial fluid as well as HCO3- ions to bile by a mechanism independent of Na(+)-H+ exchange.

The origin of and subcellular mechanisms causing pancreatic bicarbonate secretion.

In recent years, there has been a rapid growth in knowledge about the subcellular mechanisms involved in pancreatic ductal secretion of bicarbonate. The mechanisms governing anion transport across the luminal membrane of duct cells have been well characterized. Evidence suggests that the cystic fibrosis transmembrane conductance regulator is a cyclic adenosine monophosphate-regulated Cl- conductance in the luminal membrane that plays a pivotal role in ductal bicarbonate secretion by recirculating the Cl- imported into duct cells through Cl(-)-HCO3- exchange. The mechanisms governing ion transfer across the basolateral plasma membrane of duct cells are less well defined. There is some evidence suggesting that secretin may cause exocytotic insertion of proton pumps into the basolateral plasma membrane. Once inserted into the plasma membrane, proton pumps could engage in primary active electrogenic H+ ion transport to interstitial tissue while secondary active HCO3- secretion occurs over the luminal membrane through Cl(-)-HCO3- exchangers coupled in parallel with the cystic fibrosis transmembrane conductance regulator. These and other subcellular phenomena related to ductal secretory function are reviewed.

Na(+)-H+ exchange is not important for pancreatic HCO3- secretion in the pig.

UNLABELLED: Pancreatic inter- and intralobular duct cells extrude H(+)-ions to interstitial fluid when they secrete HCO3- to pancreatic juice. This study assesses the potential importance of Na(+)-H(+)-ion exchange for H(+)-ion extrusion and secretion of HCO3-, using the Na(+)-H+ exchange blockers amiloride and hexamethylene-amiloride. Intracellular pH (pHi) in inter- and intralobular pancreatic duct epithelium was measured using BCECF fluorescence. H(+)-ion efflux was measured using a NH4Cl prepulse, acid-loading technique. In HCO3(-)-free media, pHi recovery following acid loading was blocked by amiloride (10(-4) M) and hexamethylene-amiloride (10(-6) M), demonstrating amiloride- and hexamethylene-amiloride-sensitive Na(+)-H+ exchange. However, 5 x 10(-6) M hexamethylene-amiloride did not reduce secretin-dependent pancreatic HCO3- secretion in vivo. Maximal H(+)-efflux through Na(+)-H+ exchange was 1.5 +/- 0.2 mumol min-1 ml cell volume-1, i.e. less than 1% of estimated net H(+)-ion efflux during HCO3- secretion. CONCLUSION: amiloride- and hexamethylene amiloride sensitive Na(+)-H+ exchange is not important for secretin-dependent pancreatic HCO3- secretion in the pig. Other mechanisms for H+ extrusion dominate.

Intravenous bilirubin infusion causes vacuolization of the cytoplasm of hepatocytes and canalicular cholestasis.

To examine whether intravenous bilirubin infusion causes cholestasis and impairs liver metabolism, bile secretion and ethanol clearance were measured in 34 anaesthetized pigs before and after intravenous infusion of 0.5 mumol kg-1 min-1 bilirubin for 4.5 hours. Bilirubin infusion increased plasma bilirubin to 556 +/- 76 mumol l-1 and hepatic tissue bilirubin to 3.5 +/- 1.3 mmol kg tissue weight-1. Bilirubin infusion depressed bilirubin secretion and net hepatic uptake of cholate and taurocholate, and caused a 86 +/- 6% reduction of cholate-induced bile secretion. Bilirubin caused formation of large cytoplasmic vacuoles in hepatocytes and dilatation of bile canaliculi. Ethanol clearance and secretin-dependent ductular bile secretion were unaffected by bilirubin. We conclude that intravenous infusion of unconjugated bilirubin causes accumulation of bilirubin in the liver, vacuolization of the hepatocyte cytoplasm and canalicular but not ductular cholestasis. The canalicular cholestasis is not due to impaired hepatic mitochondrial energy metabolism, but may be due to inhibition of a common pathway for lipid, bilirubin and bile salt secretion from hepatocytes.

Secretin dissipates red acridine orange fluorescence from pancreatic duct epithelium.

This study was undertaken to elucidate whether duct cells in the pancreas contain acidic cytoplasmic compartments regulated by secretin. Microdissected pancreatic ducts from pigs were examined by acridine orange (AO) and 2',7'-biscarboxyethyl-5(6)-carboxyfluorescein/tetraacetoxymethy l ester (BCECF/AM) epifluorescence microscopy. Estimated cytoplasmic pH using BCECF fluorescence was 7.43 +/- 0.04 and was not changed by altering CO2 tension in the incubation medium. The epithelium of acridine orange incubated peripheral interlobular pancreatic ducts exhibited green and red fluorescence; the colour depending on the experimental conditions. Red epithelial fluorescence was seen in resting pancreatic ducts and was greatly accentuated by raising CO2 in the incubation medium from 5.5 to 10 kPa. The red fluorescence was abolished by secretin, or following incubation with chloroquine or NH4Cl or the protonophores carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) or carbonyl cyanide m-chlorophenylhydrazone (CCCP), leaving uniform green fluorescence. These findings suggest that pancreatic duct cells contain CO2-dependent acidic compartments which vanish during secretin stimulation and which may be cytoplasmic tubulovesicles.

Colchicine blocks the effects of secretin on bile duct cell tubulovesicles and plasma membrane geometry and impairs ductular HCO3- secretion in the pig.

Secretin causes the bile duct cells to secrete HCO3-. To examine whether the transformation of duct cell ultrastructure that follows secretin stimulation depends on microtubules and is important for ductular HCO3- secretion, we examined the effect of colchicine on ductular HCO3- secretion and on the morphology of cells lining bile ductules of anaesthetized pigs. Colchicine blocked secretin-dependent cytoplasmic clearance of tubulovesicles and prevented expansion of the basolateral plasma membrane in duct cells and reduced the ductular HCO3- secretory response from 132 +/- 25 mumol min-1 to 97 +/- 14 mumol min-1. In contrast, lumicolchicine did not affect secretin-dependent tubulovesicle clearance or plasma membrane geometry or ductular HCO3- secretion. Accordingly, secretin-dependent cytoplasmic clearance of tubulovesicles in bile duct cells appears to depend on microtubules and to be important for ductular HCO3- secretion.

Colchicine inhibits the effects of secretin on pancreatic duct cell tubulovesicles and HCO3- secretion in the pig.

Secretin stimulation clears the cytoplasm of intralobular pancreatic duct cells in pigs of tubulovesicles and causes these cells to secrete HCO3- into the pancreatic juice. To determine whether the clearance of cytoplasmic tubulovesicles involves the microtubule system and is important for initiation of HCO3- secretion, the effect of the microtubule poison colchicine on duct cell morphology and pancreatic HCO3- secretion was measured in anaesthetized pigs. Before colchicine, secretin reduced the density of tubulovesicles in the cytoplasm of pancreatic duct cells from 92 +/- 8 U to 8 +/- 2 U and initiated pancreatic secretion of 176 +/- 21 mumols min-1 HCO3-. After colchicine, secretin failed to lower duct cell tubulovesicle density and caused the secretion of only 77 +/- 14 mumols min-1 HCO3-. By contrast, lumicolchicine, an isomer of colchicine that does not affect microtubules, did not inhibit pancreatic HCO3- secretion. Colchicine did not reduce carbonic anhydrase or Na,K-ATPase activities in in-vitro assays. The clearance of tubulovesicles from the cytoplasm of pancreatic duct cells therefore seems to be microtubule-dependent and important for the pancreatic HCO3- secretion.

Importance of carbonic anhydrase for canalicular and ductular choleresis in the pig.

To assess the importance of carbonic anhydrase (CA) for canalicular and ductular choleresis, the effect of acetazolamide on bile secretion was measured in three experimental groups of anaesthetized pigs. CA activity in liver homogenate was 46 (43-54) U g-1 wet weight, 150 mg kg-1 b.w. acetazolamide completely abolished the CA activity. Acetazolamide reduced bile HCO3- secretion in six secretin infused, bile-acid depleted pigs by 67 (58-71)% at arterial pH 7.41 (7.38-7.46). By contrast, acetazolamide did not affect HCO3- secretion in six Na-taurocholate (TCA) infused pigs in the absence of secretin stimulation. Acetazolamide reduced ursodeoxycholic-acid- (UDCA) dependent HCO3- secretion by 24 (11-38)% in six other pigs in the absence of secretin stimulation. Histochemical examination using modifications of Hansson's method showed strong reaction in bile ductules and weaker reaction in peripheral zones of liver lobules. Because acetazolamide impairs HCO3- secretion from cells sustaining high rates of H+/HCO3- transport, it is suggested that high rates of H+/HCO3- transport are confined to bile ductules under conditions of secretin- and UDCA-induced choleresis.