Iron deficiency and anemia: disparity exists between children in American Samoa and children living within the US.

BACKGROUND/OBJECTIVES: Healthy People 2010 emphasizes elimination of health disparity and improvements in anemia and iron deficiency (ID). The study purpose was to (1) determine the prevalence of anemia, ID and ID anemia (IDA) in children living in American Samoa and (2) compare the prevalence to that found in children living in the United States. SUBJECTS/METHODS: A total of 211 children from American Samoa, aged 1-5 years of age, participated in this cross-sectional study. Prevalence of anemia, ID and IDA were determined and comparison made using data obtained from children living in the United States. Anemia was diagnosed as hemoglobin (Hb) <110.0 g/l, ID as erythrocyte protoporphyrin (EP) >70 mumol/mol heme and IDA as Hb <110.0 g/l and EP >70 mumol/mol heme. RESULTS: Anemia, ID and IDA prevalence was 33, 70 and 33%, respectively. The results of children from the United States were as follows: anemia, 9%; ID, 10% and IDA, 2%. Within American Samoan children, ID is positively associated with being breastfed <6 months (P<0.05) and anemia and IDA with lower household income (P<0.05; P<0.01). Mean Hb was significantly lower (P<0.001) and mean EP was significantly higher (P<0.001) than those within children living in the United States. CONCLUSION: To meet Healthy People 2010 goals in children aged 1-2 years, the prevalence of ID in children living in American Samoa would need to decrease from 83 to 5% and in children aged 3-5 years from 59 to 1%. It is critical to ensure that populations within the United States and its territories are provided appropriate resources to promote health and prevent disease.

U.S. Army dietitians deploy in support of Cobra Gold: a humanitarian mission.

Dietitians are multifunctional and play an important role in humanitarian missions as educators, planners, and consultants. Three dietitians deployed to Thailand in support of the 16th Annual Joint and Combined Exercise, Cobra Gold 1997. The goal of the Medical Civic Assistance Program (MEDCAP) was to promote long-term public health improvements in rural Thai villages. The dietitians counseled 140 patients and taught an additional 5,300 individuals during nutrition classes. The primary nutrition-related clinical diagnoses included malnutrition, anemia, diabetes, hypertension, goiter, and poor appetite. The dietitian who deployed as the medical planner and MEDCAP executive officer facilitated coordination and planning for all phases of the MEDCAP operation. The teams were made up of U.S. and Thai military forces and Thai civilian medical personnel. The mission requirements were established with the Royal Thai Supreme Command, Thai governors, Ministry of Public Health officers, military and medical officers, and veterinarians of the three provinces.

Inhibitory effect of thyrotropin-releasing hormone on enzyme secretion from isolated rat pancreatic acinar cells.

This study reports a direct effect of TRH on amylase secretion from isolated rat exocrine pancreatic acinar cells. TRH inhibited carbachol (10(-5) M)-stimulated amylase secretion by a maximum of 24% at a concentration of 10(-11) M (p < 0.05), but did not affect basal amylase release in concentrations from 10(-13) M to 10(-8) M. Ceruletide (3 x 10(-10) M)-stimulated amylase secretion was maximally reduced by 23% at a TRH concentration of 10(-10) M (p < 0.05). Direct stimulation of protein kinase C-mediated secretion by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) was not altered by TRH. The TRH metabolite cyclo (His-Pro) did not influence basal or stimulated pancreatic secretion in vitro. These findings point to a TRH-mediated modulation of exocrine pancreatic secretion at the receptor site.

[Effect of thyrotropin releasing hormone and histidyl-proline diketopiperazine on enzyme section of isolated pancreatic acinar cells of the rat]. / Einfluss von Thyrotropin-Releasing-Hormon und Histidyl-Prolin-Diketopiperazin auf die Enzymsekretion von isolierten Pankreasazinuszellen der Ratte.

The effect of thyrotropin-releasing hormone (TRH) and histidyl-proline-diketopiperazine [cyclo (His-Pro), CHP] on amylase secretion from isolated rat exocrine pancreatic acinar cells was investigated. TRH showed a dose-dependent inhibition of carbachol-stimulated amylase secretion with a maximum of 24% at a concentration of 10(-11) M (p < 0.05). Basal amylase release was not affected in concentrations from 10(13) M to 10(-8) M. CHP did not influence basal or carbachol-stimulated pancreatic secretion in vitro. These results suggest that TRH in contrast to CHP may play a role in the paracrine regulation of exocrine pancreatic secretion.

Inhibition of pancreatic secretion under long-term octreotide treatment in humans.

The somatostatin analogue octreotide (SMS 201-995) is a potent inhibitor of human exocrine pancreatic secretion. In the present study we analyzed the effect of octreotide (3 x 100 micrograms, daily) given over a time period of 7 days on hormone-stimulated exocrine pancreatic secretion in 6 healthy volunteers using a secretin-ceruletide test. The secretin-ceruletide test was carried out before, following the first injection of octreotide (day 1) and after a 7-day treatment with 3 x 100 micrograms octreotide daily. Duodenal fluid was collected over 30 min without stimulation, over 60 min following a bolus injection of 1 U/kg body weight secretin, and over 60 min during a continuous infusion of secretin and ceruletide. Following the first injection of octreotide and following 7 days of octreotide treatment secretin/ceruletide-stimulated amylase secretion was significantly reduced. Trypsin and chymotrypsin secretion was significantly reduced after the first injection of octreotide when pancreatic secretion was stimulated by secretin and ceruletide simultaneously. However, secretin and ceruletide-induced trypsin and chymotrypsin secretion was not inhibited after 7 days of octreotide treatment. Baseline, secretin and secretin/ceruletide-stimulated bicarbonate output were not influenced by octreotide either following the first injection of octreotide or the 7 days' treatment. Octreotide is a potent inhibitor of secretin/ceruletide-stimulated pancreatic amylase, trypsin and chymotrypsin secretion. However, following a 7-day treatment with octreotide this inhibition is only persistent for pancreatic amylase secretion.

Exocrine pancreatic secretion in man following one week of M1-muscarinic receptor blockade.

A double-blind, randomized, placebo-controlled crossover study was performed to assess the influence of one week of selective M1-muscarinic receptor blockade on pancreatic exocrine secretion in man. Ten healthy subjects received telenzepine (3 mg p.o.) and placebo each for 8 days, with a 6-day drug-free washout interval between treatment sequences. On Day 8 of each sequence, pancreatic secretion was stimulated for 2 h by infusion of submaximal secretin (0.2 U.kg/h) followed by maximal stimulation with secretin (1.0 U.kg/h) and ceruletide (120 ng.kg/h). Telenzepine had no significant effect on secretory parameters during submaximal stimulation with secretin. During maximal stimulation, total protein, secretory volume, and output of amylase, trypsin and bicarbonate were unexpectedly increased by telenzepine. These findings might be partially explained by removal of the inhibitory influence of pancreatic polypeptide, which was depressed by telenzepine. Acute studies have shown that M1-receptor antagonists inhibit exocrine secretion. Our results suggest that adaptation of physiological mechanisms governing the exocrine pancreas may occur after one week of receptor blockade by a therapeutic dosage of telenzepine, to the extent that M1-blockade no longer inhibits secretion.

[The value of ultrasound and computerized tomography in detection of cystic changes in chronic pancreatitis]. / Wertigkeit von Sonographie und Computertomographie im Nachweis von zystischen Veränderungen bei chronischer Pankreatitis.

Intra- or extrapancreatic pseudocysts (PP) are the most common local complication in chronic pancreatitis. Aim of this study was to investigate frequency, localisation and size of pseudocysts in patients with chronic pancreatitis by means of ultrasound (US) and computed tomography (CT). 155 patients (females 35, males 120) with chronic pancreatitis, that underwent simultaneous (within two weeks) CT and US examinations, from January 1982 to June 1989, were included in this study. Cystic lesions were detected in 62% by CT, in 52% by US. Sensitivity in detection of cysts based on intraoperative findings (gold standard) was 98% for CT and 94% for US. 80% of the pseudocysts were smaller than 6 cm. 46% were in the range from 2 to 66 cm and 34% were smaller than 2 cm. The most common localisation was the pancreatic head region (50%), 20 of 102 patients with chronic pancreatitis were found to have a direct communication of a pseudocyst with the ductal system by ERP. No specific clinical or laboratory pattern were associated with the presence of pseudocysts. Increased pancreatic serum amylase concentration was detected in 29% of patients with and in 27% of patients without pseudocysts.

[The diagnostic value of the amino acid absorption test in detection of a disorder of exocrine pancreatic function]. / Die diagnostische Wertigkeit des Aminosäurenabsorptionstests beim Nachweis einer exokrinen Pankreasfunktionsstörung.

The amino acid consumption test (AACT) during exogenous stimulation with secretin and CCK was proposed as a sensitive and highly specific test for detection of exocrine pancreatic insufficiency. To further investigate the diagnostic value of this test we measured the AACT in comparison with the pancreolauryl serum test (PLT) in patients with chronic pancreatitis and in patients with gastrointestinal diseases but without pancreatic disease. A total of 48 patients, 23 patients with chronic pancreatitis (CP) and 25 patients with gastrointestinal diseases, were included in the study. Diagnosis of chronic pancreatitis was established by standardized morphological criteria in ultrasound, ERCP, CT, and was confirmed by surgery in 11 cases. The PLT was abnormal in 83% of patients with chronic pancreatitis and normal in 92% of the control subjects (diagnostic accuracy 88%). Basal amino acid concentration was comparable in patients with chronic pancreatitis and in control subjects (300 +/- 12 [symbol: see text] 325 +/- 16 mumol/l). The peak decrease of amino acids occurred after 30 min during combined stimulation with secretin and ceruletide and was not different between the two groups (CP: 11.2 +/- 1.7%, controls: 13.9 +/- 1.9% below basal values). With a 12% decrease of amino acids as cutoff, sensitivity was 74% and specificity 52% (diagnostic accuracy 63%). Integrated amino acid decrease did not show any significant differences between CP and controls (CP: 228 +/- 63% min, controls: 397 +/- 80% min). Determination of the individual amino acids serine, valine, histidine, and isoleucine could also not discriminate between patients with chronic pancreatitis and other gastrointestinal diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylase release from streptolysin O-permeabilized pancreatic acinar cells. Effects of Ca2+, guanosine 5'-[gamma-thio]triphosphate, cyclic AMP, tetanus toxin and botulinum A toxin.

The molecular requirements for amylase release and the intracellular effects of botulinum A toxin and tetanus toxin on amylase release were investigated using rat pancreatic acinar cells permeabilized with streptolysin O. Micromolar concentrations of free Ca2+ evoked amylase release from these cells. Maximal release was observed in the presence of 30 microM free Ca2+. Ca(2+)-stimulated, but not basal, amylase release was enhanced by guanosine 5'-[gamma-thio]triphosphate (GTP[S]) (3-4 fold) or cyclic AMP (1.5-2 fold). Neither the two-chain forms of botulinum A toxin and tetanus toxin, under reducing conditions, nor the light chains of tetanus toxin, inhibited amylase release triggered by Ca2+, or combinations of Ca2+ + GTP[S] or Ca2+ + cAMP. The lack of inhibition was not due to inactivation of botulinum A toxin or tetanus toxin by pancreatic acinar cell proteolytic enzymes, as toxins previously incubated with permeabilized pancreatic acinar cells inhibited Ca(2+)-stimulated [3H]noradrenaline release from streptolysin O-permeabilized adrenal chromaffin cells. These data imply that clostridial neurotoxins inhibit a Ca(2+)-dependent mechanism which promotes exocytosis in neural and endocrine cells, but not in exocrine cells.

Inhibition of human exocrine pancreatic secretion by the long-acting somatostatin analogue octreotide (SMS 201-995).

The new long-acting somatostatin analogue octreotide (SMS 201-995) was investigated for its influence on secretagogue-stimulated human exocrine pancreatic secretion. Eighteen healthy volunteers participated in the study. During duodenal intubation with a background stimulation of either secretin 1 U.kg/h or secretin 1 U.kg/h + ceruletide, 120 ng.kg/h, octreotide was infused at doses of 5, 20 and 80 micrograms/h in a placebo-controlled randomized double-blind crossover trial. Duodenal juice samples were collected in 10-min intervals, and amylase, trypsin, chymotrypsin, and bicarbonate were measured in the individual fractions. During secretin stimulation, amylase was inhibited between 41 and 59%, trypsin between 28 and 72%, chymotrypsin between 55 and 70%, and bicarbonate between 0 and 31% with 5, 20 and 80 micrograms/h octreotide. During secretin and ceruletide stimulation, amylase was significantly inhibited by 84%, 78%, 81%, trypsin by 76%, 55%, 52%, chymotrypsin by 77%, 55%, 60%, and bicarbonate by 25%, 11%, 19% with 5, 20, and 80 micrograms/h octreotide, respectively (all decreases P less than 0.05). The long-acting somatostatin analogue octreotide was confirmed to be a potent inhibitor of stimulated human exocrine pancreatic secretion. The near maximal inhibitory potency of octreotide was achieved at a dose of only 5 micrograms/h. This finding may be of value in the planning of therapeutic studies with octreotide.

Influence of colloidal bismuth subcitrate on enzyme secretion from isolated rat pancreatic acinar cells.

Bismuth salts are currently used as monotherapy or in combination with antibiotics for the treatment of Helicobacter pylori-associated peptic ulcer disease. Besides encouraging clinical results with colloidal bismuth subcitrate (CBS), there is an ongoing fear of organ toxicity with the use of bismuth salts. To study potential toxic effects of CBS under short-term exposure, we tested the influence of CBS on amylase secretion from isolated rat pancreatic acinar cells under basal conditions and following carbachol (CCh) and ceruletide (CRT) stimulation. Basal secretion was reduced by 8.9 +/- 9.6% (n = 10) (mean +/- SEM) (P < 0.05), 5.2 +/- 9.2% (P < 0.05), 9.4 +/- 6.4% (P < 0.01), and 6.2 +/- 12.2% (P < 0.05) with 0.001, 0.01, 0.1, and 1 micrograms/ml CBS, respectively. With 10 micrograms/ml and 100 micrograms/ml CBS, basal amylase secretion was increased in a dose-dependent manner, by 13.7 +/- 11.7% (P < 0.05) and 24.5 +/- 12.8% (P < 0.01). CCh (10(-5) M)- and CRT (3 x 10(-10) M)-stimulated secretory responses were not altered significantly by any of the CBS doses used. In concentrations above 1 microgram/ml, CBS increased pancreatic amylase secretion. Amylase secretion in response to secretagogues was not affected by CBS. These findings are unlikely to be associated with a toxic effect of CBS on exocrine pancreatic acinar cell function.

Decavanadate displaces inositol 1,4,5-trisphosphate (IP3) from its receptor and inhibits IP3 induced Ca2+ release in permeabilized pancreatic acinar cells.

Inositol 1,4,5-trisphosphate (IP3) induced Ca2+ release in digitonin permeabilized rat pancreatic acinar cells is specifically inhibited by decavanadate. The Ca2+ release induced with 0.18 microM IP3 is half maximally inhibited with approximately 5 microM decavanadate. Complete inhibition is achieved with around 20 microM decavanadate. Removal of decavanadate from the permeabilized cells fully restores sensitivity towards IP3, indicating the reversibility of the inhibition. Oligovanadate, which inhibits ATP dependent Ca2+ uptake into intracellular stores, does not influence IP3 induced Ca2+ release. In order to reveal the mechanism underlying the effects of the different vanadate species, binding of IP3 to the same cellular preparations was investigated. We found that binding of IP3 to a high affinity receptor site (Kd approx. 1.2 nM) could be abolished by decavanadate but not by oligovanadate. With 0.5 microM decavanadate, IP3 binding was half maximally inhibited. A similar potency of decavanadate was also found with adrenal cortex microsomes which bind IP3 with the same affinity (Kd approx. 1.4 nM) as permeabilized pancreatic acinar cells. Labelled IP3 was displaced from these subcellular membranes with similar kinetics by unlabelled IP3 and decavanadate. The data suggest that the inhibitory action of decavanadate on IP3 induced Ca2+ release is a consequence of its effect on binding of IP3 to its receptor.

Clinical picture and diagnosis of acute pancreatitis.

Acute pancreatitis is characterized by clinical, morphological, and functional aspects. Severe abdominal pain with progression during the first hours after onset is the leading symptom. In the majority of patients acute pancreatitis had a "mild" clinical course, but 10 to 20% will develop severe local and systemic complications. Symptoms at the onset of disease are not specific and need consideration of several other diagnoses. Elevation of pancreatic serum enzymes is the main parameter in the diagnosis of acute pancreatitis. Besides the traditional parameter of total amylase, several specific pancreatic enzymes (e.g. pancreatic amylase, lipase, immunoreactive trypsin or elastase) are now widely used in clinical routine and guarantee a higher diagnostic specificity. The imaging procedures ultrasonography and computed tomography aid in identifying etiological factors in grading the severity of the disease and deciding therapeutic strategies. Endoscopic retrograde chol- angiopancreatography is most sensitive in detecting biliary lithiasis and can be successfully complemented by sphincterotomy if needed. Besides complex clinical and laboratory criteria, several biochemical markers (e.g. C-reactive protein, PMN-elastase, trypsinogen activation peptides) have been found to be valid for the detection of pancreatic necrosis and are of definite prognostic value. On the basis of such detailed information, the therapeutic strategy can be planned in a straight-forward manner.

Serum ribonuclease activity in the diagnosis of pancreatic disease.

The present study evaluated serum ribonuclease activity (SRA) in patients with inflammatory and neoplastic pancreatic diseases. RNase determination was carried out using t-RNA (T) from E. coli MRE 600 at pH 7.4 and polycytidylic acid (poly-C) (P) at pH 6.6 as RNA substrates with RNase A from bovine pancreas as reference enzyme. Healthy volunteers had a SRA of T: 160 +/- 12 and P: 482 +/- 24 ngeq/mL (mean +/- SEM (n]. In patients with acute interstitial pancreatitis (AIP), SRA was similar to healthy controls (T: 166 +/- 14; P: 474 +/- 30 ngeq/mL). Patients with acute necrotizing pancreatitis (ANP) had increased SRA (T: 278 +/- 49; P: 791 +/- 145 ngeq/mL, p less than 0.01, compared to controls). SRA values were also increased in patients with chronic pancreatitis (CP) with T: 224 +/- 15 ngeq/mL (p less than 0.01) and in patients with pancreatic carcinoma (PCA) with T: 331 +/- 35 (p less than 0.001 vs controls, p less than 0.01 vs CP). Increased SRA was detected in patients with renal insufficiency (T: 2576 +/- 195 ngeq/mL, p less than 0.001). Diagnostic discrimination between AIP and ANP was achieved in 69% using T-SRA (sensitivity 31%, specificity 88%), and in 78% using P-SRA (sensitivity 54%, specificity 92%). Discrimination between CP and pancreatic carcinoma was possible in 68% (sensitivity 67%, specificity 71%). The diagnostic value of serum RNase is limited because of its low sensitivity, but increased T-SRA above a cutoff of 250 ngeq/mL and increased P-SRA above a cutoff of 620 ngeq/mL are specific for detecting pancreatic necrosis in the absence of renal impairment. The kidney is a major site for SRA clearance.

Effect of GTP and Ca2+ on inositol 1,4,5-trisphosphate induced Ca2+ release from permeabilized rat exocrine pancreatic acinar cells.

The effects of Ca2+ and GTP on the release of Ca2+ from the inositol 1,4,5-trisphosphate (IP3) sensitive Ca2+ compartment were investigated with digitonin permeabilized rat pancreatic acinar cells. The amount of Ca2+ released due to IP3 directly correlated with the amount of stored Ca2+ and was found to be inversely proportional to the medium free Ca2+ concentration. Ca2+ release induced by 0.18 microM IP3 was half maximally inhibited at 0.5 microM free Ca2+, i.e. at concentrations observed in the cytosol of pancreatic acinar cells. GTP did not cause Ca2+ release on its own, but a single addition of GTP (20 microM) abolished the apparent desensitization of the Ca2+ release which was observed during repeated IP3 applications. This effect of GTP was reversible. GTP gamma S could not replace GTP. Desensitization still occurred when GTP gamma S was added prior to GTP. The reported data indicate that GTP, stored Ca2+ and cytosolic free Ca2+ modulate the IP3 induced Ca2+ release.

Characterization of inositol 1,4,5-trisphosphate-sensitive (IsCaP) and -insensitive (IisCaP) nonmitochondrial Ca2+ pools in rat pancreatic acinar cells.

We have measured Ca2+ uptake and Ca2+ release in isolated permeabilized pancreatic acinar cells and in isolated membrane vesicles of endoplasmic reticulum prepared from these cells. Ca2+ uptake into cells was monitored with a Ca2+ electrode, whereas Ca2+ uptake into membrane vesicles was measured with 45Ca2+. Using inhibitors of known action, such as the H+ ATPase inhibitors NBD-Cl and NEM, the Ca2+ ATPase inhibitor vanadate as well as the second messenger inositol 1,4,5-trisphosphate (IP3) and its analog inositol 1,4,5-trisphosphorothioate (IPS3), we could functionally differentiate two nonmitochondrial Ca2+ pools. Ca2+ uptake into the IP3-sensitive Ca2+ pool (IsCaP) occurs by a MgATP-dependent Ca2+ uptake mechanism that exchanges Ca2+ for H+ ions. In the absence of ATP Ca2+ uptake can occur to some extent at the expense of an H+ gradient that is established by a vacuolar-type MgATP-dependent H+ pump present in the same organelle. The other Ca2+ pool takes up Ca2+ by a vanadate-sensitive Ca2+ ATPase and is insensitive to IP3 (IisCaP). The IsCaP is filled at "higher" Ca2+ concentrations (approximately 10(-6) mol/liter) which may occur during stimulation. The low steady-state [Ca2+] of approximately 10(-7) mol/liter is adjusted by the IisCaP. It is speculated that both Ca2+ pools can communicate with each other, the possible mechanism of which, however, is at present unknown.

Characterization of MgATP-driven H+ uptake into a microsomal vesicle fraction from rat pancreatic acinar cells.

In microsomal vesicles, as isolated from exocrine pancreas cells, MgATP-driven H+ transport was evaluated by measuring H+-dependent accumulation of acridine orange (AO). Active H+ uptake showed an absolute requirement for ATP with simple Michaelis-Menten kinetics (Km for ATP 0.43 mmol/liter) with a Hill coefficient of 0.99. H+ transport was maximal at an external pH of 6.7, generating an intravesicular pH of 4.8. MgATP-dependent H+ accumulation was abolished by protonophores, such as nigericin (10(-6) mol/liter) or CCCP (10(-5) mol/liter), and by inhibitors of nonmitochondrial H+ ATPases, such as NEM or NBD-Cl, at a concentration of 10(-5) mol/liter. Inhibitors of both mitochondrial and nonmitochondrial H+ pumps, such as DCCD (10(-5) mol/liter) or Dio 9 (0.25 mg/ml), reduced microsomal H+ transport by about 90%. Vanadate (2 x 10(-3) mol/liter), a blocker of those ATPases, which form a phosphorylated intermediate, did not inhibit H+ transport. The stilbene derivative DIDS (10(-4) mol/liter), which inhibits anion transport systems, abolished H+ transport completely. MgATP-dependent H+ transport was found to be anion dependent in the sequence Cl- greater than Br- greater than gluconate-; in the presence of SO2-4, CH3COO- or No-3, no H+ transport was observed. MgATP-dependent H+ accumulation was also cation dependent in the sequence K+ greater than Li+ greater than Na+ = choline+. As shown by dissipation experiments in the presence of different ion gradients and ionophores, both a Cl- and a K+ conductance, as well as a small H+ conductance, were found in the microsomal membranes. When membranes containing the H+ pump were further purified by Percoll gradient centrifugation (ninefold enrichment compared to homogenate), no correlation with markers for endoplasmic reticulum, mitochondria, plasma membranes, zymogen granules or Golgi membranes was found. The present data indicate that the H+ pump located in microsomes from rat exocrine pancreas is a vacuolar- or "V" -type H+ ATPase and has most similarities to that described in endoplasmic reticulum, Golgi apparatus or endosomes.

Anion channels in giant liposomes made of endoplasmic reticulum vesicles from rat exocrine pancreas.

Using the method of dehydration and rehydration, rough endoplasmic reticulum (RER) vesicles, isolated by differential centrifugation, can be enlarged to giant liposomes with diameters ranging from 5 to 200 micron. Patch-clamp studies on these giant RER liposomes revealed the existence of a channel with a mean conductance of 260 +/- 7 pS (n = 23; 140 mmol/liter KCl on both sides). The channel is about four times more permeable for Cl- than for K+. Its activity is strongly voltage regulated. At low potentials (+/- 20 mV) the channel is predominantly in its open state with an open probability near 1.0, whereas it closes permanently at high positive and negative voltages (+/- 70 mV). The channel activity is not influenced by changing the free Ca2+ concentration from 1 mmol/liter to less than 10(-9) mol/liter on either side, and is also not affected by typical Cl- -channel blockers like diphenylamine-2-carboxylate (DPC, 1 mmol/liter) or 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS, 1 mmol/liter). Another chloride channel with a single-channel conductance of 79 +/- 6 pS (n = 4) was less frequently observed. In the potential range of -80 to +40 mV this channel displayed no voltage-dependent gating. We assume that these anion channels are involved in the maintenance of electroneutrality during Ca2+ uptake in the RER.

Anion dependence of Ca2+ transport and (Ca2+ + K+)-stimulated Mg2+-dependent transport ATPase in rat pancreatic endoplasmic reticulum.

Anion dependence of (Ca2+ + K+)-stimulated Mg2+-dependent transport ATPase and its phosphorylated intermediate have been characterized in both "intact" and "broken" vesicles from endoplasmic reticulum of rat pancreatic acinar cells using adenosine 5'-[gamma-32P] triphosphate ([gamma-32P]ATP). In intact vesicles (Ca2+ + K+)-Mg2+-ATPase activity was higher in the presence of Cl- or Br- as compared to NO3-, SCN-, cyclamate-, SO4(2-) or SO3(2-). Incorporation of 32P from [gamma-32P]ATP into the 100-kDa intermediate of this Ca2+ATPase was also higher in the presence of Cl-, Br-, NO3- or SCN- as compared to cyclamate-, SO4(2-) or SO3(2-). When the membrane permeability barrier to anions was abolished by breaking vesicle membrane with the detergent Triton X-100 (0.015%) (Ca2+ + K+)-Mg2+ATPase activity in the presence of weakly permeant anions, such as SO4(2-) and cyclamate-, increased to the level obtained with Cl-. However, 32P incorporation into 100-kDa protein was still higher in the presence of Cl- as compared to cyclamate-, indicating a direct effect of Cl- on the Ca2+ATPase molecule. The anion transport blocker 4,4-diisothiocyanostilbene-2,2-disulfonate (DIDS) inhibited (Ca2+ + K+)-Mg2+ATPase activity to about 10% of the Cl- stimulation level, irrespective of the sort of anions present in both intact and broken vesicles. This indicates a direct effect of DIDS on (Ca2+ + K+)-Mg2+ATPase. K+ ionophore valinomycin influenced (Ca2+ + K+)-Mg2+ATPase activity according to the actual K+ gradient: Ko+ greater than Ki+ caused inhibition, Ko+ less than Ki+ caused stimulation. From these results we conclude that Ca2+ transport into endoplasmic reticulum is coupled to ion movements which must occur to maintain electroneutrality.