Human monoclonal antibody MBL-HCV1 delays HCV viral rebound following liver transplantation: a randomized controlled study.

Rapid allograft infection complicates liver transplantation (LT) in patients with hepatitis C virus (HCV). Pegylated interferon-α and ribavirin therapy after LT has significant toxicity and limited efficacy. The effect of a human monoclonal antibody targeting the HCV E2 glycoprotein (MBL-HCV1) on viral clearance was examined in a randomized, double-blind, placebo-controlled pilot study in patients infected with HCV genotype 1a undergoing LT. Subjects received 11 infusions of 50 mg/kg MBL-HCV1 (n=6) or placebo (n=5) intravenously with three infusions on day of transplant, a single infusion on days 1 through 7 and one infusion on day 14 after LT. MBL-HCV1 was well-tolerated and reduced viral load for a period ranging from 7 to 28 days. Median change in viral load (log10 IU/mL) from baseline was significantly greater (p=0.02) for the antibody-treated group (range -3.07 to -3.34) compared to placebo group (range -0.331 to -1.01) on days 3 through 6 posttransplant. MBL-HCV1 treatment significantly delayed median time to viral rebound compared to placebo treatment (18.7 days vs. 2.4 days, p<0.001). As with other HCV monotherapies, antibody-treated subjects had resistance-associated variants at the time of viral rebound. A combination study of MBL-HCV1 with a direct-acting antiviral is underway.

Successful algorithm for selective liver biopsy in the right hepatic lobe live donor (RHLD).

Routine versus selective predonation liver biopsy (LBx) remains controversial for assuring the safety of right hepatic lobe live donor (RHLD). Between December 1999 and March 2007, 403 potential RHLD were evaluated; 142 donated. Indications for selective LBx were: abnormal liver function tests or imaging studies, body mass index (BMI) >28, history of substance abuse or family history of immune mediated liver disease. All donors had a LBx at the time of surgery. Of 403 potential RLD, 149(36.9%) were accepted as donors, 25(6.3%) had their recipient receive a deceased donor graft, 94(23.4%) were rejected, 52(12.9%) stopped the evaluation process, 76(18.8%) withdrew from the process and 7(1.7%) are currently completing evaluation. Eighty-seven (21.5%) met criteria and were biopsied. Seventy-three (83.9%) had either normal (n = 24) or macrosteatosis <10% (n = 49); 51 of these donated. Abnormal LBx eliminated 15 potential donors. No significant abnormalities were found in donation biopsies of donors not meeting algorithm criteria. Three of 87 (3.4%) had complications requiring overnight admission (2 for pain, 1 for bleeding; transfusion not required). Use of this algorithm resulted in 78% of potential donors avoiding biopsy and potential complications. No significant liver pathology was identified in donors not meeting criteria for evaluation LBx. Routine predonation LBx is unnecessary in potential RHLD.

Cost-effectiveness of screening patients for hepatitis C.

This review discusses the benefits and drawbacks of public health screening for hepatitis C, its cost effectiveness, and the various strategies to identify individuals infected with the hepatitis C virus (HCV). Of the estimated 4 million people infected with hepatitis C in the United States, approximately 50% are unaware of their infection. Both the high incidence and recent improvements in the treatment of hepatitis C make it likely that a screening program for this disease would be beneficial to patients, their families, and to the public. Testing for anti-HCV antibody is now widely available, automated, sensitive (>95%), and relatively inexpensive (approximately $80 per test). Interferons and the introduction of ribavirin into the treatment armamentarium have improved the effectiveness of therapy. Lifestyle modifications can be made to decrease the risk of transmission, and patients can be counseled to avoid alcohol consumption and receive hepatitis A and hepatitis B vaccinations, if appropriate. An additional benefit of early detection is that family members can be alerted to the risk factors for hepatitis C. Such education increases overall public awareness of the disease and may improve prevention efforts. Several national agencies within the United States and in Europe have issued guidelines for hepatitis C screening. Each of these calls for screening of high-risk populations, which include individuals who have received blood products and intravenous drug users. Targeted screening and improved treatment outcomes will likely show identification of those with hepatitis C to be cost effective in the future.

Lung abcess complicating Legionella micdadei pneumonia in an adult liver transplant recipient: case report and review.

Legionella micdadei (Pittsburgh pneumonia agent) is the second most common cause of Legionella pneumonia, and occurs predominantly in immunocompromised hosts. L micdadei is the cause of nosocomial pneumonia in renal transplant recipients, but has not been described in other adult solid organ transplant recipients. This report describes the first case of L micdadei pneumonia in an adult liver transplant recipient on immunosuppressive therapy. Importantly, this case highlights the difficulties in establishing the diagnosis, as the Legionella urinary antigen is negative, and special culture conditions are required. Furthermore, this case illustrates several atypical clinical features of L micdadei pneumonia in a transplant recipient, including a community acquired mode of transmission, occurrence several years after organ transplantation, and lung abcess formation. The patient was successfully treated with limited surgical resection and quinolone antimicrobial monotherapy.

Relationship between hepatitis C genotype and severity of recurrent hepatitis C after liver transplantation.

BACKGROUND: Recurrence of hepatitis C virus (HCV) infection after liver transplantation is universal, but the relationship between hepatitis C genotype and posttransplant outcome has been controversial. The aim of this study was to assess the relationship between hepatitis C genotype on posttransplant frequency of recurrent hepatitis, histologic severity of recurrence, and progression to cirrhosis. METHODS: We studied 42 HCV RNA positive patients who received transplants between 1985 and 1994. Sera were tested for HCV RNA and protocol liver biopsies were in obtained the posttransplant period. Biopsies were scored according to the histologic activity index (HAI) and staged in a blinded fashion. RESULTS: The distribution of hepatitis C genotypes distribution was as follows: 1a, 19 (45%); 1b, 17 (40%); 2b, 3 (7%); and 1 each of 2a, 3a, and 4a. There was histologic evidence of hepatitis in 38 of 42 (90.4%) of patients. Hepatitis C was mild, moderate, or severe (HAI>3) in 38% of grafts and minimal (HAI 0-3) in 62%. Overall HAI scores and histologic stage were higher in the genotype 1b group. Six of 17 (35%) genotype 1b patients had cirrhosis compared with 2 of 25 (8%) in the non-1b genotype group. CONCLUSIONS: (1) Histologic evidence of recurrent hepatitis C is seen in 90% of liver allografts; (2) Histologic hepatitis C recurs with similar frequency in genotype 1b and non-1b recipients; (3) Genotype 1b is associated with more severe histologic disease recurrence than non-1b genotypes; (4) Genotype 1b appears to be associated with a higher degree of posttransplant fibrosis and cirrhosis than non-1b genotypes.

Recurrent hepatitis B, hepatitis C, and combined hepatitis B and C in liver allografts: a comparative pathological study.

Although recurrence of viral hepatitis in liver transplants is common, data comparing recurrent hepatitis B (HB), hepatitis C (HC), and co-existing dual hepatitis B and C (HB&C) are sparse. Posttransplantation liver biopsies, along with molecular, serological, immunohistochemical, and clinical data from 27 patients with pretransplantation diagnosis of chronic viral hepatitis, were reviewed. The patients were placed into 4 groups: Group I, with pretransplantation HB (n = 8); group II, with pretransplantation HC (n = 10); group III with pretransplantation HC and anti-HB surface or core antibody (n = 4); and group IV, with pretransplantation HB&C (n = 5). The histopathologic findings and patient outcome were compared in the 4 groups. A high rate of recurrence of viral hepatitis was seen for all 4 groups: Group I = 100%, group II = 90%, Group III = 100%, and group IV = 80%, with the mean (median) recurrence time of 308 (224), 82 (52), 61 (64), and 125 (70) days, respectively. The number of deaths (their median survival times) were: group I = 4 (374 days), group II = 4 (794 days), group III = 1 (1,143 days), and group IV = 5 (448 days). The earliest histological findings of lobular injury was the presence of acidophil bodies and Kupffer cell hyperplasia, the latter being more prominent in recurrent HC cases. Recurrent HB presented in 2 forms: early (before 150 days) with poor survival and with either severe necroinflammatory histology or with features of fibrosing cholestatic hepatitis, and delayed (after 150 days), with mild necro-inflammatory activity and prolonged survival. HC with or without anti-HB antibodies had early recurrence, but the course was slowly progressive. Patients with HB&C had recurrence of both viruses; however, the course was dictated by HB virus.

Adult-to-adult live donor liver transplantation: a short-term clinicopathologic study.

With the success of pediatric live donor liver transplantation (LDLT) and the continued shortage of cadaveric donors, adult-to-adult LDLT has been performed at some centers, including ours. We performed a detailed histologic review of all liver specimens obtained from 9 adult recipients at and after LDLT and correlated these findings with the patients' course and outcome. Five patients had histologic evidence of biliary tract pathology; 3 of 5 required surgical or radiologic intervention. The other 2 had clinically insignificant biliary disease. Diffuse hepatocytic hemorrhagic necrosis secondary to massive portal blood flow after portal venous revascularization resulted in graft failure and retransplantation in a single patient with severe preoperative portal hypertension. Two perioperative deaths were caused by sepsis and multiorgan failure (day 25) and generalized thrombosis related to factor V Leiden (day 6). The preoperative diagnosis, presence of portal vein thrombosis in the native liver, postoperative cholangiopathy, and subcapsular hemorrhagic necrosis in donor liver wedge biopsies did not affect the short-term outcome. In conclusion, biliary tract pathology is common after adult-to-adult LDLT but does not negatively affect graft or patient survival. Infrequent but catastrophic vascular complications related to portal hemodynamics or thrombosis can result in graft loss and/or patient death.

Multimodality treatment of hepatocellular carcinoma in a hepatobiliary specialty center.

OBJECTIVES: To review the experience of the treatment of hepatocellular carcinoma by a single multimodality team during a 6-year period, including all patients who were referred for possible surgical intervention, to evaluate prognostic factors at presentation, and to determine the results of the different modalities of treatment that were used. DESIGN: Retrospective study of 154 patients who were referred to our Hepatobiliary Surgical Unit with the diagnosis of hepatocellular carcinoma from January 1988 through August 1995. SETTING: Tertiary care center. RESULTS: Methods of treatment included surgical resection (n=49), transplantation (n=22), hepatic artery chemoembolization (n=30), systemic chemotherapy (n=25), and no treatment (n=22). Predictive prognostic factors included coexisting cirrhosis, symptoms at presentation, and abnormal liver function test results. Unfavorable tumor characteristics were size (diameter, >5 cm) and multicentricity. For patients who underwent surgical exploration, advanced staging according to the manual of the American Joint Committee on Cancer, vascular invasion, and a margin of less than 1 cm in the group for patients who underwent resection impacted negatively on the prognosis. The median survival (42.4 months) for the group of patients who underwent resection was significantly higher than that for the groups of patients who did not undergo resection. Chemoembolization was associated with significantly better survival results than was systemic chemotherapy. CONCLUSIONS: Hepatic resection offers the best chance at cure for patients with hepatocellular carcinoma. The high association between hepatocellular carcinoma and cirrhotic liver disease makes surgical resection, even in favorable tumor types, a difficult task based on low hepatic reserve whose tumors are considered unresectable can be considered for chemoembolization. Liver transplantation should be reserved for selected patients with cirrhotic liver disease who have tumors (diameter, <5 cm) in the contest of neoadjuvant protocols.

Live donor adult liver transplantation using right lobe grafts: donor evaluation and surgical outcome.

HYPOTHESIS: Live donor adult liver transplantation (LDALT) is a safe and efficacious treatment for patients with end-stage liver disease. DESIGN: Case-control study. SETTING: Hepatobiliary surgery and liver transplantation unit. PATIENTS: From December 10, 1998, through April 10, 2000, a single team performed 15 LDALT procedures with 2 simultaneous living donor kidney transplants. During this period, 66 potential donors were screened and evaluated. INTERVENTIONS: Potential donors were evaluated with 3-dimensional helical computed tomographic scan, including volume renderings for hepatic lobar volume, vascular anatomy, virtual resection planes, and morphologic features. Suitable donors undergo complete medical and psychiatric evaluation and preoperative arteriography. MAIN OUTCOME MEASURES: Donor demographics, evaluation data, operative data, hospital length of stay, and morbidity. RESULTS: A total of 38 men (58%) and 28 women (42%) were evaluated with 15 donors participating in LDALT. Two additional donors provided kidney grafts for simultaneous transplantation at the time of LDALT. Thirty-two donors (48%) were rejected for either donor or recipient reasons, and 10 patients (15%) elected not to participate after initial screening. Three-dimensional volume renderings by helical computed tomographic scan predicted right lobe liver volume within 92% of actual graft volume. Donor morbidity, including all complications, was 67% with no mortality. Residual liver regenerated to approximately 70% of initial volume within 1 week and 80% within 1 month after surgery. CONCLUSIONS: Donor evaluation is an important component of LDALT. Significant donor morbidity is encountered even with careful selection. To minimize donor morbidity, groups considering initiating living donor programs should have expertise in hepatic resection and vena cava preservation using the "piggyback" technique during liver transplantation.

Effect of nifedipine on renal function in liver transplant recipients receiving tacrolimus.

The effect of nifedipine on renal function in liver transplant recipients who were receiving tacrolimus was evaluated between January 1992 and January 1996. Two groups of patients receiving tacrolimus were compared over a period of 1 year, one group comprising hypertensive patients who were receiving nifedipine, and the other comprising nonhypertensive patients not receiving nifedipine. The time from transplant to baseline was similar in all patients. Nifedipine significantly improved kidney function as indicated by a significant lowering of serum creatinine levels at 6 and 12 months. The observed positive impact of nifedipine on reducing the nephrotoxicity associated with tacrolimus in liver transplant recipients should be an important factor in selecting an agent to treat hypertension in this population.

Histologic recurrence-free outcome after orthotopic liver transplantation for chronic hepatitis B.

Recurrent hepatitis B (HB) following orthotopic liver transplantation (OLT) for chronic disease is common. However, an unpredictable minority of patients follow a recurrence-free course. Clinical, virologic, and pathologic data from patients surviving longer than 60 days (n=24) with pathologically confirmed nonrecurrence of HB following OLT for chronic HB were reviewed to identify factors associated with nonrecurrence of HB. Nine of 24 patients had no histologic and immunohistologic evidence of recurrent HB. In addition to pre-OLT hepatitis B e antigen (HBeAg) negativity, coexisting delta and anti-HB therapy/prophylaxis, other acquired viral infections and their therapy, and severe acute rejection due to noncompliance were considered the possible protective factors against HB recurrence in these 9 patients. Histologic and, particularly immunopathologic, evaluation of liver biopsies must be utilized in definitively diagnosing recurrence of HB.

Hyperdynamic circulation in portal hypertension: a comparative model of arterio-venous fistula.

Complications of portal hypertension remain perplexing physiologic phenomena in the understanding of shunt hemodynamics with multiple theories. Hyperdynamic circulation was also found in sepsis, chronic anemia and arterio-venous (A-V) fistula which relate to an increase in nitric oxide. We hypothesize that portosystemic collaterals may mimic an A-V fistula in which the high-pressure portal blood connects with the lower pressure systemic venous circulation. Although these collaterals decompress the portal circulation, a number of secondary hemodynamic phenomena occur which increase portal blood flow and tend to counteract the portal hypotensive effect of the portosystemic shunt. The consequent increases in cardiac output and portal blood flow perfuse the compromised liver. As portal blood flow increases, collateral flow increases and is nearly totally shunted in the systemic circulation. This shunt may eventually introduce a vicious cycle of hyperdynamic circulation into a compromised host. Ultimately, high-output cardiac failure occurs, leading to cirrhotic cardiomyopathy.

Improved survival after live donor adult liver transplantation (LDALT) using right lobe grafts: program experience and lessons learned.

We present our program experience with 85 live donor adult liver transplantation (LDALT) procedures using right lobe grafts with five simultaneous live donor kidney transplants using different donors performed over a 6-year period. After an "early" 2-year experience of 25 LDALT procedures, program improvements in donor and recipient selection, preoperative imaging, donor and recipient surgical technique and immunosuppressive management significantly reduced operative mortality (16% vs. 3.3%, p = 0.038) and improved patient and graft 1-year survival in recipients during our "later" experience with the next 60 cases (January 2001 and March 2005; patient survival: early 70.8% vs. later 92.7%, p = 0.028; graft survival: Early 64% vs. later 91.1%, p = 0.019, respectively). Overall patient and graft survival were 82% and 80%. There was a trend for less postoperative complications (major and minor) with program experience (early 88% vs. later 66.7%; p = 0.054) but overall morbidity remained at 73.8%. Biliary complications (cholangitis, disruption, leak or stricture) were not influenced by program experience (early 32% vs. later 38%). Liver volume adjusted to 100% of standard liver volume (SLV) within 1 month post-transplant. Despite a high rate of morbidity after LDALT, excellent patient and graft survival can be achieved with program experience.

Nonalcoholic steatohepatitis.

OBJECTIVE: To determine the clinical relevance of nonalcoholic steatohepatitis (NASH) and to review the available literature on the epidemiology, clinical features, histology, pathogenesis, clinical course, and management of this condition. DATA SOURCES: Pertinent articles in English identified through a MEDLINE search (1966 to the present) and the bibliographies of relevant articles. STUDY SELECTION: All studies, including case reports, evaluating the salient features and clinical profile of NASH. DATA EXTRACTION: Data were selected from all articles that fit the study selection criteria. DATA SYNTHESIS: Nonalcoholic steatohepatitis is a distinct clinical entity characterized by elevated plasma liver enzyme levels and liver biopsy findings that are identical to those seen in alcoholic hepatitis; patients with NASH, however, do not consume alcohol in quantities known to cause liver injury. Patients with NASH are typically obese, middle-aged women with asymptomatic hepatomegaly who are diabetic or hyperlipidemic and present with an unrelated medical problem. Analysis of liver biopsy specimens is the cornerstone of diagnosis; hepatic morphologic findings range from mild fatty degeneration and inflammation to cell degeneration, fibrosis, and cirrhosis with or without the presence of Mallory hyaline bodies. Elevated levels of free fatty acids in the liver are thought to be responsible for the development of steatohepatitis. Although NASH is most often a benign disease with an indolent course, patients with this condition occasionally develop cirrhosis, portal hypertension, and hepatic failure. In some cases, NASH may be reversed with weight reduction. CONCLUSION: Nonalcoholic steatohepatitis is an important differential diagnosis for asymptomatic patients with chronically elevated plasma liver enzyme levels, especially if obesity, diabetes, or hyperlipidemia are present. Analysis of liver biopsy specimens is necessary for diagnosis and must be done in all patients with unexplained abnormal liver function and negative results on a noninvasive workup. Prognosis is good in most patients. The precise role of weight reduction and ursodeoxycholic acid therapy in the favorable alteration of the natural history of this disorder needs to be addressed in large, well-controlled studies.

Hepatitis vaccines.

Viral hepatitis accounts for substantial morbidity and mortality worldwide, To date, the molecular sequences of six hepatotropic viruses have been described and designated hepatitis A, B, C, D, E, and G. Various methods have been employed to decrease the occurrence of these diseases, and advances in vaccination strategies have aided in prevention of viral hepatitis. There are currently two FDA-approved vaccines licensed for use in the United States, aimed at eradication of hepatitis A and hepatitis B viral infection. A considerable amount of research has been devoted to the development of these vaccines, and progress has been made toward the development of vaccines aimed at the other hepatotropic viruses. In this article, the development and current status of the vaccines directed against the hepatitis viruses are reviewed.

AST/ALT ratio predicts cirrhosis in patients with chronic hepatitis C virus infection.

OBJECTIVE: A liver biopsy is necessary to grade and stage chronic hepatitis C virus (HCV) infection. In a previous study of patients with nonalcoholic liver disease, an aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio >1 suggested cirrhosis. We sought to examine the value of the AST/ALT ratio in distinguishing cirrhotic patients with chronic HCV infection from noncirrhotic patients and to correlate the ratio with the grade and stage of hepatitis and other biochemical indices. METHODS: We retrospectively studied 139 patients with chronic HCV infection. Routine biochemical indices were determined, and the histological grade of necroinflammatory activity and the stage of fibrosis of the liver biopsy specimens were scored. RESULTS: The mean AST/ALT ratio in the cirrhotic patients (n = 47) was higher than in the noncirrhotic patients (n = 92) (1.06 +/- 0.06 vs 0.60 +/- 0.09; p < 0.001). A ratio > or =1 had 100% specificity and positive predictive value in distinguishing cirrhotic from noncirrhotic patients, with a 53.2% sensitivity and 80.7% negative predictive value. The ratio correlated positively with the stage of fibrosis but not with the grade of activity or other biochemical indices. Of the cirrhotic patients, 17% had no clinical or biochemical features suggestive of chronic liver disease except for an AST/ALT ratio > or =1. CONCLUSION: The AST/ALT ratio is a dependable marker of fibrosis stage and cirrhosis in patients with chronic HCV infection.

Sarcoidosis with selective involvement of a second liver allograft: report of a case and review of the literature.

A case of sarcoidosis recurrent in a patient's second liver allograft is described. There was no granulomatous disease seen in the patient's first liver allograft. After the second orthotopic liver transplantation (OLT), the patient was successfully treated for acute rejection, aspergillus infection, and cytomegalovirus viremia. Approximately 2 months after the second OLT, the patient was treated with long-term interferon-alpha for recurrent hepatitis C. Five years after the operation, he experienced liver failure secondary to recurrent hepatitis and underwent a third OLT. This is only the second reported case of sarcoidosis recurrent in the liver parenchyma of a transplanted organ and the first in which interferon-alpha might have played a role.

Liver transplantation for autoimmune hepatitis: a long-term pathologic study.

Autoimmune hepatitis (AIH) after liver transplantation (LT) may recur and is difficult to diagnose. Our aims were to define the histopathology of and factors related to AIH recurrence. Fourteen of 475 patients received LT for AIH; 2 died perioperatively. Liver specimens (native and post-LT biopsies) from 12 other patients were reviewed and correlated with pre- and post-LT clinical course and outcome. Recurrent AIH was seen in 5 of 12 patients, 35 to 280 days post-LT as lobular hepatitis with acidophil bodies and lymphoplasmacytic infiltrate. Portal/interface hepatitis was seen with disease progression and 2 of 5 patients developed cirrhosis. Of 7 nonrecurrent patients, 1 had acquired hepatitis C with lobular/portal hepatitis and none developed cirrhosis. Histology suggestive of overlap syndrome was seen in 3 of 12 native livers with no effect on post-LT course or pathology. High-grade necroinflammation was present in native livers at LT in 5 of 5 cases with recurrent AIH and in 1 of 7 without recurrence (P <.01). Pre-LT disease duration, donor/recipient gender distribution, HLA studies, and rejection episodes did not correlate with AIH recurrence. We conclude that (1) recurrent AIH is not uncommon and was seen in 42% of patients with lymphoplasmacytic lobular, portal, and interface hepatitis; (2) acidophil bodies with lymphoplasmacytic cells are seen in early recurrent AIH; (3) recurrent AIH appears at variable time periods post-LT, and the progression is slow; and (4) high-grade inflammation in native liver at LT is a strong predictor of recurrent AIH.

Hepatitis C infection: a rare cause of fulminant hepatic failure.

Fulminant hepatic failure is caused by a variety of viruses, toxins, and metabolic derangements. The hepatitis C virus (HCV) causes indolent development of cirrhosis and has not been associated with fulminant hepatic failure. We report the first documented case of fulminant hepatitis C in the United States. The patient developed jaundice and stage IV encephalopathy. Initial laboratory evaluation did not reveal the etiology. The patient survived without liver transplantation. Three wk later he was found to have a positive HCV RNA and anti-HCV antibody seroconversion. He continued to improve with alpha-interferon treatment and has normal liver function and a negative HCV RNA 15 months later.

Mechanisms of H+ secretion by inner medullary collecting duct cells.

Inner medullary collecting duct cells were isolated from rat papillae and grown to confluence on cover slips. H+ secretion was estimated by intracellular pH (pHi) changes measured with the fluorescent probe 2,7-biscarboxyethyl-5(6)-carboxyfluorescein. In buffered NaCl, pHi was 7.14 +/- 0.04 (n = 78). After acidification about 40% of monolayers exhibited Na+-independent alkalinization. In 5 mM glucose, cell alkalinization occurred at a rate of 47 +/- 4 nM H+/min. However, cell alkalinization did not occur in the presence of 2-deoxy-D-glucose (5-15 mM), iodoacetate (5 mM), or KCN (5 mM). All monolayers tested exhibited amiloride-inhibitable Na+-dependent cell alkalinization that appeared to be a first-order kinetic process; Km [Na+] was approximately 52 mM and Vmax was approximately 250 nM [H+]/min. At a constant extracellular [Na+] (110 mM), Na+-dependent H+ efflux was a first-order function of pHi; Km for intracellular [H+] = 321 nM and Vmax = 182 nM H+/min. The data are consistent with the presence of a primary active H+ pump and a secondary active Na+ exchanger. The metabolic energy for the active H+ pump can be provided by glycolysis and oxidative phosphorylation.