Recovery of cell volume in response to osmotic stress is mediated in part by increases in the Cl1 permeability of the plasma membrane. These studies evaluate the hypothesis that ATP release and autocrine stimulation of purinergic (P2) receptors couple increases in cell volume to opening of Cl-channels. In HTC rat hepatoma cells, swelling Epithelial cells express a variety of plasma membrane proteins that bind solutes in a selective manner and transport them to the cell interior. Although the action of such transport proteins is essential for normal cell function, the resulting increase in intracellular solute concentration leads to an influx of water and cell swelling. However, cell volume is maintained within a relatively narrow physiologic range by adaptive responses that generally involve solute efflux through opening of K+ and Clchannels and restoration of cell volume toward its resting state (1-3). Despite extensive study, the mechanisms that couple increases in cell volume to opening of ion channels remain incompletely understood.In a number of cell types, swelling-induced opening of Clchannels is dependent on the presence of intracellular ATP (4, 5). This ATP dependence of volume-stimulated channel opening is attributable, in part, to the action of intracellular protein kinases on channels or channel regulatory proteins (6, 7). However, other mechanisms are possible as well. Recent experimental evidence suggests that ATP can also function outside of the cell as an autocrine factor to increase membrane Cl-permeability (8). In secretory epithelia, increases in cAMP stimulate cellular release of ATP in concentrations sufficient to activate purinergic (P2) receptors in the plasma membrane, which leads to Cl-channel opening (9). The mechanisms involved in ATP trafficking in secretory cells are not fully defined, with evidence for (9, 10) and against (11) ATP release through the cystic fibrosis transmembrane conductance regulator (CFTR), a member of the ATP-binding cassette (ABC) family of proteins. Other members of the ABC family, including the multidrug resistance P-glycoprotein, are thought to regulate volume-activated channels through cellular release of ATP or other pathways (6, 12).Like secretory epithelia, activation of P2 receptors in liver cells increases membrane Cl-permeability through opening of Cl-channels (13). However, unlike secretory cells, liver cells are not thought to exhibit Cl--dependent secretion (14), and the physiologic importance of purinergic signaling in liver has not been defined. Based on the prominent role of Cl-ions in liver cell volume regulation (15), we have proposed that volume-dependent activation of Cl-channels is mediated by an autocrine mechanism involving ATP release and activation of a P2 receptor. In a model liver cell line that expresses P2 receptors (13, 16), we show that (i) cell swelling increases membrane ATP permeability, and (ii) Cl-channel opening and cell volume recovery from swelling each require stimulation of P2 receptors by extracellular ATP. These...

Little information is available on acute liver failure (ALF) in the United States. We gathered demographic data retrospectively for a 2-year period from July 1994 to June 1996 on all cases of ALF from 13 hospitals (12 liver transplant centers). Data on the patients included age, hepatic coma grade on admission, presumed cause, transplantation, and outcome. Among 295 patients, 74 (25%) survived spontaneously, 121 (41%) underwent transplantation, and 99 (34%) died without undergoing transplantation. Ninety-two of 121 patients (76%) survived 1 year after transplantation. Acetaminophen overdose was the most frequent cause (60 patients; 20%), followed by cryptogenic/non A non B non C (NANBNC; 15%), idiosyncratic drug reactions (12%), hepatitis B (10%), and hepatitis A (7%). Spontaneous survival rates were highest for patients with acetaminophen overdose (57%) and hepatitis A (40%) and lowest for those with Wilson's disease (no survivors of 18 patients). The transplantation rate was highest for Wilson's disease (17 of 18 patients; 94%) and lowest for autoimmune hepatitis (29%) and acetaminophen overdose (12%). Age did not differ between survivors and nonsurvivors, perhaps reflecting a selection bias for patients transferred to liver transplant centers. Coma grade on admission was not a significant determinant of outcome, but showed a trend toward affecting both survival and transplantation rate. These findings on retrospectively studied patients from the United States differ from those previously gathered in the United Kingdom and France, highlighting the need for further study of trends in each country.

Cerebral edema and intracranial hypertension, commonly present in fulminant hepatic failure, may lead to brainstem herniation and limit the survival of comatose patients awaiting liver transplantation before a donor organ becomes available. Also, they are likely responsible for postoperative neurological morbidity and mortality. Although intracranial pressure monitoring has been proposed to aid clinical decision making in this setting, its use in the prevention of brainstem herniation preoperatively, in the selection of patients for liver transplantation who have the potential for neurological recovery and in the maintenance of cerebral perfusion during liver transplantation has not been examined in detail. To address these issues, we established a protocol for intracranial pressure monitoring in comatose patients with fulminant hepatic failure as part of their preoperative and intraoperative management. Twenty adults and three children underwent intracranial pressure monitoring. Ten patients required preoperative medical therapy with mannitol, barbiturates or both for a rise in intracranial pressure above 25 mm Hg. Four patients had a sustained lowering of intracranial pressure, three of whom survived hospitalization. Six patients had intracranial hypertension refractory to medical management, were removed from a waiting list for a donor organ and died with brainstem herniation. Of the remaining 17 patients, 3 died of other causes while awaiting a donor organ, 2 recovered spontaneously without neurological sequelae and 12 underwent liver transplantation. All but one patient undergoing liver transplantation had transient intraoperative intracranial hypertension develop, requiring medical treatment. The 12 patients who had transplants recovered neurologically and were discharged from the hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Despite abundant evidence for changes in mitochondrial membrane permeability in tumor necrosis factor (TNF)-mediated cell death, the role of plasma membrane ion channels in this process remains unclear. These studies examine the influence of TNF on ion channel opening and death in a model rat liver cell line (HTC). TNF (25 ng/ml) elicited a 2-and 5-fold increase in K ؉ and Cl ؊ currents, respectively, in HTC cells. These increases occurred within 5-10 min after TNF exposure and were inhibited either by K ؉ or Cl ؊ substitution or by K ؉ channel blockers (Ba 2؉ , quinine, 0.1 mM each) or Cl ؊ channel blockers (10 M 5-nitro-2-(3-phenylpropylamino)benzoic acid and 0.1 mM N-phenylanthranilic acid), respectively. TNF-mediated increases in K ؉ and Cl ؊ currents were each inhibited by intracellular Ca 2؉ chelation (5 mM EGTA), ATP depletion (4 units/ml apyrase), and the protein kinase C (PKC) inhibitors chelerythrine (10 M) or PKC 19 -36 peptide (1 M). In contrast, currents were not attenuated by the calmodulin kinase II 281-309 peptide (10 M), an inhibitor of calmodulin kinase II. In the presence of actinomycin D (1 M), each of the above ion channel blockers significantly delayed the progression to TNF-mediated cell death. Collectively, these data suggest that activation of K ؉ and Cl ؊ channels is an early response to TNF signaling and that channel opening is Ca 2؉ -and PKC-dependent. Our findings further suggest that K ؉ and Cl ؊ channels participate in pathways leading to TNF-mediated cell death and thus represent potential therapeutic targets to attenuate liver injury from TNF.