- Email: [email protected]
Hepatitis-related hepatic erythropoietin production
]
P
Hepatitis-Related Hepatic Erythropoietin Production DAVID K.
KLASSEN, M.D., JERRY
L.
SPIVAK, M.D.,
Baltimore, Maryland
rythropoietin, the glycoprotein hormone that regulates erythropoiesis, is produced in the kidneys and to a small extent in the liver [1,2]. The contribution of hepatic erythropoietin to adult erythropoiesis appears relatively minor since erythropoietin levels are usually low in relation to the hematocrit in patients with end-stage renal disease, in whom red cell transfusions or recombinant human erythropoietin is required to maintain an adequate red cell mass [3,4]. In such patients, hepatitis of either an infectious or toxic etiology is occasionally associated with an amelioration of anemia [57], but whether this is due to an increase in erythropoietin production or to another factor is unclear. Measurements of erythropoietin production in such patients have been complicated by the presence of residual kidney tissue, which can still produce amounts of erythropoietin. We describe herein a severely anemic, transfusion-dependent, surgically anephric dialysis patient who developed erythrocytosis during an episode of acute hepatitis in association with a marked increase in serum immunoreactive erythropoietin.
E
CASE REPORT The patient, a 28-year-old transfusion-dependent male hemodialysis recipient, who had been surgically anephric for 10 years, developed gradually progressive malaise, nausea, vomiting, and abdominal discomfort 5 weeks after receiving three units of packed red cells. The serum alanine aminotransferase (ALT) level was 108 IU/L and that of serum aspartate aminotransferase (AST) was 64 IU/L (Figure 1). Hepatitis B surface antigen or antibodies were not detected on three occasions, nor were antibodies to hepatitis A or human immunodeficiency virus 1 detected. Pre-illness, acute, and convalescent IgG titers to cytomegalovirus and Epstein-Barr virus were unchanged, and IgM anti-
From the Division of Nephrology, Department of Medicine (DKK), University of Maryland School of Medicine, and the Division of Hematology, Department of Medicine (JLS), The Johns Hopkins University School of Medicine, Baltimore, Maryland. Requests for reprints should be addressed to David K. Klassen, M.D., Divisionof Nephrology, University of Maryland Hospital, 22 South Greene Street, Baltimore, Maryland 21201. Manuscript submitted February 21, 1990, and accepted in revised form June 14, 1990.
684
November 1990 The American Journal of Medicine
bodies to these viruses were not found. Alpha-fetoprotein levels were normal at 4.4 ng/mL and 3.8 ng/ mL at 7 and 9 weeks, respectively, after the onset of symptoms. Serum albumin, total hemolytic complement, total bilirubin, and the prothrombin time were normal. An abdominal computed tomographic scan revealed only a small perihepatic fluid collection. A clinical diagnosis of non-A, non-B hepatitis was made. Ten days after the onset of symptoms, the hematocrit was 23%. During the period of clinical symptoms, which lasted 10 weeks, it continued to increase in a linear fashion, reaching a peak of 47% before declining gradually to the previous baseline of 19%. During this interval, there were no changes in other factors that might have influenced erythropoiesis such as the frequency or duration of dialysis, blood urea nitrogen or serum creatinine levels, protein or vitamin intake, or changes in the serum parathyroid hormone level. The patient was a nonsmoker. The serum ALT and AST levels continued to fluctuate and were persistently abnormal for the next 14 months. The patient has recently started receiving recombinant human erythropoietin to prevent the development of cardiac insufficiency due to anemia. Serum samples collected weekly before, during, and after the marked change in hematocrit were analyzed for erythropoietin (Figure 1) using a sensitive and specific commercially available radioimmunoassay (Smith-Kline Bioscience, Van Nuys, California), which uses recombinant-derived reagents [8]. Serum immunoreactive erythropoietin correlates well with biologically active serum erythropoietin using this assay. The mean serum erythropoietin level in nonanemic men is 12 ± 0.8 mU/ mL (range: 3 to 21 mU/mL) and in anephric patients, 11.5 + 4.0 mU/mL (range: 5 to 35 mU/mL). As shown in Figure 1, serum immunoreactive erythropoietin before the episode of hepatitis ranged from 3 to 21 mU/mL. Coincident with the initial observed rise in serum transaminases, the level rose to 99 mU/mL. When the ALT level fell, serum erythropoietin also dropped to 19 mU/mL. Subsequent increments in ALT were associated with elevations of serum erythropoietin to as high as 480 mU/mL. When the patient's clinical symp-
Volume 89
HEPATITIS-RELATEDERYTHROPOIETINPRODUCTION / KLASSENAND SPIVAK
toms resolved, serum erythropoietin levels declined to the normal range despite continued elevations of the ALT level. This was followed by a decrease in the hematocrit to 19%. Two and 14 months later, serum erythropoietin levels were 8 mU/mL and 9 lmU/mL, respectively, despite persistent ALT elevations (Figure 1).
50%-
P 40%TRANS-
~ 30%-
COMMENTS 20%,
Studies of erythropoietin mRNA expression as well as in situ hybridization studies employing a cDNA probe for the hormone have established conclusively that the liver, as well as the kidney, is a site of erythropoietin production [1,2,9]. Experimental 400 observations suggest that erythropoietin producz tion in the liver is suppressed and less subject to physiologic regulation than renal erythropoietin production. Animal studies have shown that the 200 liver can produce erythropoietin in response to partial hepatectomy or toxic livery injury. Hepatic erythropoietin production following partial hepatectomy is greatest during the period of maximal NOV 0E¢ JAN FEB MAR APR MAY OCT hepatocyte proliferation and increase in liver mass. )c Following nephrectomy and partial hepatectomy in the rat, erythropoietin levels peak coincident with ~G maximal liver regeneration and decline when liver regeneration is complete [10,11]. Similar results are seen with toxic hepatic injury induced by carbon tetrachloride [12]. Interestingly, hepatic production of erythropoietin in these situations appears to 5C remain under some degree of physiologic control. Nephrectomized rats made hypoxic will have increased erythropoietin levels. Hepatectomy abolo o~, .'.ov oh ,',. ,', .;. ,;. ishes this effect [13]. Renal production of erythropoietin appears to down-regulate the liver's ability Figure 1. Hematocrit, serum erythropoietin, and serum ALT to synthesize erythropoietin. Toxic liver injury or values before, during, and after an episode of non-A, non-B Clinical symptoms of hepatitis lasted 10 weeks and hepatectomy fails to increase erythropoietin levels hepatitis. resolved at the time the hematocrit began to return to basein non-nephrectomized animals [11,12]. line. The serum ALT fluctuated but remained elevated for 14 Clinical observations have shown that anephric months. dialysis patients have markedly diminished but not absent erythropoietin levels and are able to main- tamol. These cases suggest that the elevated red tain a severely down-regulated erythropoiesis that blood cell volume that occasionally has been associis still responsive to physiologic stress [3,4]. The ated with hepatitis in dialysis patients is a nonability of the liver to make small amounts of eryth- specific reaction to liver injury and not the result of ropoietin may be subject to change with liver dis- changes induced by a viral genome or a specific ease. Hepatitis has been associated with increases toxin. There are few data on erythropoietin levels in in red cell production in dialysis patients. Kolkhepatitis-associated erythrocytosis. Brown et al Vegter et al [5] described 11 patients with elevated [15] described a patient with hepatitis-associated hemoglobin levels during an outbreak of viral hepaelevations of red blood cell production who concurtitis in a dialysis unit. Simon et al [14] reported 30 patients, including two anephric patients, with in- rently had an elevated plasma erythropoietin level. creased hemoglobin and reticulocyte counts during This case was complicated by the presence of a nonepisodes of hepatitis. These cases included hepati- functioning transplanted kidney. Severely diseased tis due to hepatitis B and cytomegalovirus as well as nonfunctioning kidneys have been reported to prodrug-induced hepatitis associated with allopurinol, duce significant amounts of erythropoietin, which fluoxymesterone, methyldopa, aspirin, and parace- can elevate the red blood cell mass [16]. Meyrier
II
g,
November 1990 The American Journal of Medicine
Volume 89
685
HEPATITIS-RELATED ERYTHROPOIETIN PRODUCTION / KLASSEN AND SPIVAK
et al [7] described an anephric patient with an
elevated erythropoietin level during an episode of hepatitis. In this case, however, erythropoietin levels before the episode of hepatitis were not measured. By using a sensitive and specific radioimmunoassay in the current patient, we have documented that the rise and fall in hematocrit associated with an episode of presumed viral hepatitis was preceded by a marked increase and a subsequent decline in serum immunoreactive erythropoietin. These data suggest that hepatic erythropoietin is immunologically and biologically similar to renal erythropoietin and that the lack of erythropoietin was the primary cause of anemia in this surgically anephric dialysis patient. Since erythropoietin levels declined in the presence of ongoing hepatocellular injury, it appears that expression of the erythropoietin gene is either not influenced by hepatocellular damage per se or that the site of synthesis of erythropoietin in the liver is not the hepatocyte. It has been suggested that the reticuloendothelial system is the source of hepatic erythropoietin. Hyperplasia of Kupffer cells induced by administration of zymosan or colloidal carbon in the absence of hepatocyte injury results in increases of erythropoietin in hypoxic nephrectomized rats [17]. Kupffer cell activity markedly increases during hepatic regeneration following hepatectomy [18]. Using in situ hybridization, Vogt et al [19] have shown that murine macrophages express the erythropoietin gene. The exact cell responsible for hepatic erythropoietin production remains, however, controversial [20]. It is of interest that the duration of the patient's elevated erythropoietin levels correlated closely with the duration of clinical symptoms. Duration of clinical symptoms did not correlate with serum transaminase levels or other conventional measures of liver function. The regenerating liver has been reported to produce other substances such as ~fetoprotein [21]. The role of altered production of biologically active molecules in the generation of symptoms associated with hepatitis is unknown. This patient demonstrates that the increased erythropoiesis occasionally associated with hepatic injury is the result of the production of large amounts of erythropoietin. The regulation of erythropoietin synthesis in this infrequently observed
686
November 1990
The American Journal of Medicine
syndrome is poorly understood. Our patient's severe cardiomyopathy may have played a role analogous to the requirement of hypoxic stress in animal studies.
REFERENCES 1. Beru N, McDonald J, Lacombe C, GoldwasserE. Expressionof the erythropoietin gene. Mol Cell Biol 1986; 6: 2571-5. 2. Bondurant MC, Koury MJ. Anemia induces accumulation of erythropoietin mRNA in the kidney and liver. Mol Cell Biol 1986; 6: 2731-3. 3. Caro J, Brown S, Miller O, Murray T, ErsievAJ. Erythropoietin levels in uremic nephric and anephric patients. J Lab Ciin Med 1979; 93: 449-58. 4. Cotes PM. Immunoreactive erythropoietin in serum. Br J Haemato11982; 50: 427-38. 5. Kolk-Vegter AJ, Bosch E, van Leeuwen AM. Influence of serum hepatitis on hemoglobin level in patients on regular hemodialysis. Lancet 1971; 1: 526-8. 6. Brown S, Caro J, ErslevAJ, Murray TG. Spontaneous increase in erythropoietin and hematocrit value associated with transient liver enzyme abnormalities in an anephric patient undergoing hemodialysis. Am J Med 1980; 68: 280-4. 7. Meyrier A, Simon P, Sofia G, Brissot P. Uremia and the liver. Nephron 1981; 29: 3-6. 8. EgrieJC, Cotes AM, LaneJ, Gaines DASRE,Tam RC. Development of radioimmunoassays for human erythropoietin using recombinant erythropoietin as tracer and immunogen. J Immunol Methods 1987; 99: 235-41. 9. Lacombe C, Da Silva J-L, Bruneval P, et aL Peritubular cells are the site of erythropoietin synthesis in the murine hypoxic kidney. J Clin Invest 1988; 81: 620-3. 10. Naughton BA, Kaplan SM, Roy M, Burdowski AJ, Gordon AS, Piliero SJ. Hepatic regeneration and erythropoietin production in the rat. Science 1977; 196: 301-2. 11. Anagnostou A, Schade S, Barone J, Fried W. Effects of partial hepatectomy on extrarenal erythropoietin production in rats. Blood 1977; 50: 457-62. 12. Fried W, Barone J, Schade S, Anagnostou A. Effects of carbon tetrachloride on extrarenal erythropoietin production in rats. J Lab Clin Med 1979; 93: 700-5. 13. Fried W. The liver as a source of extrarenal erythropoietin production. Blood 1972; 40: 671-7. 14. Simon P, Meyrier A, Tanquerel T, Ang KS. Improvement of anemia in hemodialyzed patients after viral or toxic hepatic cytolysis. Br Med J 1980; 280: 8928. 15. Brown S, Caro J, ErslevA, Murray T. Spontaneous increase in erythropoietin and hematocrit value associated with transient liver enzyme abnormalities in an anephric patient undergoing hemodialysis. Am J Med 1980; 68: 280-3. 16. Dagher FJ, Ramos E, Erslev AJ, Alongi SV, Karmi SA, Caro J. Are the native kidneys responsible for erythrocytosis in renal allorecipients? Transplantation 1979; 28: 496-8. 17. Peschle C, Marone G, Genovese A, Rapport IA, Condoreli M. Increased erythropoietin production in rats with hyperplasia of the reticuloendothelial system induced by colloidal carbon or zymosan. Blood 1976; 47: 325-37. 18. Widmann JJ, Fahimi HD. Proliferation of mononuclear phagocytes (Kupffer cells) and endothelial cells in regenerating rat liver. Am J Patho11975; 80: 34966. 19. Vogt Ch, Pentz S, Rich IN. A role for the macrophage in normal hemopoiesis: III. In vitro and in vivo erythropoietin gene expression in macrophages detected by in situ hybridization. Exp Hematol 1989; 17: 391-7. 20. Erslev AJ, Caro J, Kansu E, Silver R. Renal and extrarenal erythropoietin production in anemic rats. Br J Hematol 1980; 45: 65-72. 21. Sell S, Nichols N, Becher FF, Leffert HL. Hepatocyte proliferation and alphafetoprotein in pregnant, neonatal, and partially hepatectomized rats. Cancer Res 1974; 34: 865-71.
Volume 89
P
Hepatitis-Related Hepatic Erythropoietin Production DAVID K.
KLASSEN, M.D., JERRY
L.
SPIVAK, M.D.,
Baltimore, Maryland
rythropoietin, the glycoprotein hormone that regulates erythropoiesis, is produced in the kidneys and to a small extent in the liver [1,2]. The contribution of hepatic erythropoietin to adult erythropoiesis appears relatively minor since erythropoietin levels are usually low in relation to the hematocrit in patients with end-stage renal disease, in whom red cell transfusions or recombinant human erythropoietin is required to maintain an adequate red cell mass [3,4]. In such patients, hepatitis of either an infectious or toxic etiology is occasionally associated with an amelioration of anemia [57], but whether this is due to an increase in erythropoietin production or to another factor is unclear. Measurements of erythropoietin production in such patients have been complicated by the presence of residual kidney tissue, which can still produce amounts of erythropoietin. We describe herein a severely anemic, transfusion-dependent, surgically anephric dialysis patient who developed erythrocytosis during an episode of acute hepatitis in association with a marked increase in serum immunoreactive erythropoietin.
E
CASE REPORT The patient, a 28-year-old transfusion-dependent male hemodialysis recipient, who had been surgically anephric for 10 years, developed gradually progressive malaise, nausea, vomiting, and abdominal discomfort 5 weeks after receiving three units of packed red cells. The serum alanine aminotransferase (ALT) level was 108 IU/L and that of serum aspartate aminotransferase (AST) was 64 IU/L (Figure 1). Hepatitis B surface antigen or antibodies were not detected on three occasions, nor were antibodies to hepatitis A or human immunodeficiency virus 1 detected. Pre-illness, acute, and convalescent IgG titers to cytomegalovirus and Epstein-Barr virus were unchanged, and IgM anti-
From the Division of Nephrology, Department of Medicine (DKK), University of Maryland School of Medicine, and the Division of Hematology, Department of Medicine (JLS), The Johns Hopkins University School of Medicine, Baltimore, Maryland. Requests for reprints should be addressed to David K. Klassen, M.D., Divisionof Nephrology, University of Maryland Hospital, 22 South Greene Street, Baltimore, Maryland 21201. Manuscript submitted February 21, 1990, and accepted in revised form June 14, 1990.
684
November 1990 The American Journal of Medicine
bodies to these viruses were not found. Alpha-fetoprotein levels were normal at 4.4 ng/mL and 3.8 ng/ mL at 7 and 9 weeks, respectively, after the onset of symptoms. Serum albumin, total hemolytic complement, total bilirubin, and the prothrombin time were normal. An abdominal computed tomographic scan revealed only a small perihepatic fluid collection. A clinical diagnosis of non-A, non-B hepatitis was made. Ten days after the onset of symptoms, the hematocrit was 23%. During the period of clinical symptoms, which lasted 10 weeks, it continued to increase in a linear fashion, reaching a peak of 47% before declining gradually to the previous baseline of 19%. During this interval, there were no changes in other factors that might have influenced erythropoiesis such as the frequency or duration of dialysis, blood urea nitrogen or serum creatinine levels, protein or vitamin intake, or changes in the serum parathyroid hormone level. The patient was a nonsmoker. The serum ALT and AST levels continued to fluctuate and were persistently abnormal for the next 14 months. The patient has recently started receiving recombinant human erythropoietin to prevent the development of cardiac insufficiency due to anemia. Serum samples collected weekly before, during, and after the marked change in hematocrit were analyzed for erythropoietin (Figure 1) using a sensitive and specific commercially available radioimmunoassay (Smith-Kline Bioscience, Van Nuys, California), which uses recombinant-derived reagents [8]. Serum immunoreactive erythropoietin correlates well with biologically active serum erythropoietin using this assay. The mean serum erythropoietin level in nonanemic men is 12 ± 0.8 mU/ mL (range: 3 to 21 mU/mL) and in anephric patients, 11.5 + 4.0 mU/mL (range: 5 to 35 mU/mL). As shown in Figure 1, serum immunoreactive erythropoietin before the episode of hepatitis ranged from 3 to 21 mU/mL. Coincident with the initial observed rise in serum transaminases, the level rose to 99 mU/mL. When the ALT level fell, serum erythropoietin also dropped to 19 mU/mL. Subsequent increments in ALT were associated with elevations of serum erythropoietin to as high as 480 mU/mL. When the patient's clinical symp-
Volume 89
HEPATITIS-RELATEDERYTHROPOIETINPRODUCTION / KLASSENAND SPIVAK
toms resolved, serum erythropoietin levels declined to the normal range despite continued elevations of the ALT level. This was followed by a decrease in the hematocrit to 19%. Two and 14 months later, serum erythropoietin levels were 8 mU/mL and 9 lmU/mL, respectively, despite persistent ALT elevations (Figure 1).
50%-
P 40%TRANS-
~ 30%-
COMMENTS 20%,
Studies of erythropoietin mRNA expression as well as in situ hybridization studies employing a cDNA probe for the hormone have established conclusively that the liver, as well as the kidney, is a site of erythropoietin production [1,2,9]. Experimental 400 observations suggest that erythropoietin producz tion in the liver is suppressed and less subject to physiologic regulation than renal erythropoietin production. Animal studies have shown that the 200 liver can produce erythropoietin in response to partial hepatectomy or toxic livery injury. Hepatic erythropoietin production following partial hepatectomy is greatest during the period of maximal NOV 0E¢ JAN FEB MAR APR MAY OCT hepatocyte proliferation and increase in liver mass. )c Following nephrectomy and partial hepatectomy in the rat, erythropoietin levels peak coincident with ~G maximal liver regeneration and decline when liver regeneration is complete [10,11]. Similar results are seen with toxic hepatic injury induced by carbon tetrachloride [12]. Interestingly, hepatic production of erythropoietin in these situations appears to 5C remain under some degree of physiologic control. Nephrectomized rats made hypoxic will have increased erythropoietin levels. Hepatectomy abolo o~, .'.ov oh ,',. ,', .;. ,;. ishes this effect [13]. Renal production of erythropoietin appears to down-regulate the liver's ability Figure 1. Hematocrit, serum erythropoietin, and serum ALT to synthesize erythropoietin. Toxic liver injury or values before, during, and after an episode of non-A, non-B Clinical symptoms of hepatitis lasted 10 weeks and hepatectomy fails to increase erythropoietin levels hepatitis. resolved at the time the hematocrit began to return to basein non-nephrectomized animals [11,12]. line. The serum ALT fluctuated but remained elevated for 14 Clinical observations have shown that anephric months. dialysis patients have markedly diminished but not absent erythropoietin levels and are able to main- tamol. These cases suggest that the elevated red tain a severely down-regulated erythropoiesis that blood cell volume that occasionally has been associis still responsive to physiologic stress [3,4]. The ated with hepatitis in dialysis patients is a nonability of the liver to make small amounts of eryth- specific reaction to liver injury and not the result of ropoietin may be subject to change with liver dis- changes induced by a viral genome or a specific ease. Hepatitis has been associated with increases toxin. There are few data on erythropoietin levels in in red cell production in dialysis patients. Kolkhepatitis-associated erythrocytosis. Brown et al Vegter et al [5] described 11 patients with elevated [15] described a patient with hepatitis-associated hemoglobin levels during an outbreak of viral hepaelevations of red blood cell production who concurtitis in a dialysis unit. Simon et al [14] reported 30 patients, including two anephric patients, with in- rently had an elevated plasma erythropoietin level. creased hemoglobin and reticulocyte counts during This case was complicated by the presence of a nonepisodes of hepatitis. These cases included hepati- functioning transplanted kidney. Severely diseased tis due to hepatitis B and cytomegalovirus as well as nonfunctioning kidneys have been reported to prodrug-induced hepatitis associated with allopurinol, duce significant amounts of erythropoietin, which fluoxymesterone, methyldopa, aspirin, and parace- can elevate the red blood cell mass [16]. Meyrier
II
g,
November 1990 The American Journal of Medicine
Volume 89
685
HEPATITIS-RELATED ERYTHROPOIETIN PRODUCTION / KLASSEN AND SPIVAK
et al [7] described an anephric patient with an
elevated erythropoietin level during an episode of hepatitis. In this case, however, erythropoietin levels before the episode of hepatitis were not measured. By using a sensitive and specific radioimmunoassay in the current patient, we have documented that the rise and fall in hematocrit associated with an episode of presumed viral hepatitis was preceded by a marked increase and a subsequent decline in serum immunoreactive erythropoietin. These data suggest that hepatic erythropoietin is immunologically and biologically similar to renal erythropoietin and that the lack of erythropoietin was the primary cause of anemia in this surgically anephric dialysis patient. Since erythropoietin levels declined in the presence of ongoing hepatocellular injury, it appears that expression of the erythropoietin gene is either not influenced by hepatocellular damage per se or that the site of synthesis of erythropoietin in the liver is not the hepatocyte. It has been suggested that the reticuloendothelial system is the source of hepatic erythropoietin. Hyperplasia of Kupffer cells induced by administration of zymosan or colloidal carbon in the absence of hepatocyte injury results in increases of erythropoietin in hypoxic nephrectomized rats [17]. Kupffer cell activity markedly increases during hepatic regeneration following hepatectomy [18]. Using in situ hybridization, Vogt et al [19] have shown that murine macrophages express the erythropoietin gene. The exact cell responsible for hepatic erythropoietin production remains, however, controversial [20]. It is of interest that the duration of the patient's elevated erythropoietin levels correlated closely with the duration of clinical symptoms. Duration of clinical symptoms did not correlate with serum transaminase levels or other conventional measures of liver function. The regenerating liver has been reported to produce other substances such as ~fetoprotein [21]. The role of altered production of biologically active molecules in the generation of symptoms associated with hepatitis is unknown. This patient demonstrates that the increased erythropoiesis occasionally associated with hepatic injury is the result of the production of large amounts of erythropoietin. The regulation of erythropoietin synthesis in this infrequently observed
686
November 1990
The American Journal of Medicine
syndrome is poorly understood. Our patient's severe cardiomyopathy may have played a role analogous to the requirement of hypoxic stress in animal studies.
REFERENCES 1. Beru N, McDonald J, Lacombe C, GoldwasserE. Expressionof the erythropoietin gene. Mol Cell Biol 1986; 6: 2571-5. 2. Bondurant MC, Koury MJ. Anemia induces accumulation of erythropoietin mRNA in the kidney and liver. Mol Cell Biol 1986; 6: 2731-3. 3. Caro J, Brown S, Miller O, Murray T, ErsievAJ. Erythropoietin levels in uremic nephric and anephric patients. J Lab Ciin Med 1979; 93: 449-58. 4. Cotes PM. Immunoreactive erythropoietin in serum. Br J Haemato11982; 50: 427-38. 5. Kolk-Vegter AJ, Bosch E, van Leeuwen AM. Influence of serum hepatitis on hemoglobin level in patients on regular hemodialysis. Lancet 1971; 1: 526-8. 6. Brown S, Caro J, ErslevAJ, Murray TG. Spontaneous increase in erythropoietin and hematocrit value associated with transient liver enzyme abnormalities in an anephric patient undergoing hemodialysis. Am J Med 1980; 68: 280-4. 7. Meyrier A, Simon P, Sofia G, Brissot P. Uremia and the liver. Nephron 1981; 29: 3-6. 8. EgrieJC, Cotes AM, LaneJ, Gaines DASRE,Tam RC. Development of radioimmunoassays for human erythropoietin using recombinant erythropoietin as tracer and immunogen. J Immunol Methods 1987; 99: 235-41. 9. Lacombe C, Da Silva J-L, Bruneval P, et aL Peritubular cells are the site of erythropoietin synthesis in the murine hypoxic kidney. J Clin Invest 1988; 81: 620-3. 10. Naughton BA, Kaplan SM, Roy M, Burdowski AJ, Gordon AS, Piliero SJ. Hepatic regeneration and erythropoietin production in the rat. Science 1977; 196: 301-2. 11. Anagnostou A, Schade S, Barone J, Fried W. Effects of partial hepatectomy on extrarenal erythropoietin production in rats. Blood 1977; 50: 457-62. 12. Fried W, Barone J, Schade S, Anagnostou A. Effects of carbon tetrachloride on extrarenal erythropoietin production in rats. J Lab Clin Med 1979; 93: 700-5. 13. Fried W. The liver as a source of extrarenal erythropoietin production. Blood 1972; 40: 671-7. 14. Simon P, Meyrier A, Tanquerel T, Ang KS. Improvement of anemia in hemodialyzed patients after viral or toxic hepatic cytolysis. Br Med J 1980; 280: 8928. 15. Brown S, Caro J, ErslevA, Murray T. Spontaneous increase in erythropoietin and hematocrit value associated with transient liver enzyme abnormalities in an anephric patient undergoing hemodialysis. Am J Med 1980; 68: 280-3. 16. Dagher FJ, Ramos E, Erslev AJ, Alongi SV, Karmi SA, Caro J. Are the native kidneys responsible for erythrocytosis in renal allorecipients? Transplantation 1979; 28: 496-8. 17. Peschle C, Marone G, Genovese A, Rapport IA, Condoreli M. Increased erythropoietin production in rats with hyperplasia of the reticuloendothelial system induced by colloidal carbon or zymosan. Blood 1976; 47: 325-37. 18. Widmann JJ, Fahimi HD. Proliferation of mononuclear phagocytes (Kupffer cells) and endothelial cells in regenerating rat liver. Am J Patho11975; 80: 34966. 19. Vogt Ch, Pentz S, Rich IN. A role for the macrophage in normal hemopoiesis: III. In vitro and in vivo erythropoietin gene expression in macrophages detected by in situ hybridization. Exp Hematol 1989; 17: 391-7. 20. Erslev AJ, Caro J, Kansu E, Silver R. Renal and extrarenal erythropoietin production in anemic rats. Br J Hematol 1980; 45: 65-72. 21. Sell S, Nichols N, Becher FF, Leffert HL. Hepatocyte proliferation and alphafetoprotein in pregnant, neonatal, and partially hepatectomized rats. Cancer Res 1974; 34: 865-71.
Volume 89