Lack of Guanylate Cyclase C results in increased mortality in mice following liver injury
© Mann et al; licensee BioMed Central Ltd. 2010
Received: 15 January 2010
Accepted: 2 August 2010
Published: 2 August 2010
Guanylate Cyclase C (GC-C) expression in the intestine plays a role in the regulation of fluid and ion transport, as well as epithelial cell apoptosis and proliferation. In the adult rat liver, GC-C expression is increased in response to injury. We hypothesized that GC-C is required for repair/recovery from liver injury.
We subjected wild type (WT) and GC-C deficient mice to acute liver injury with a single injection of the hepatotoxin carbon tetrachloride. Changes in the level of expression of GC-C and its ligands uroguanylin and guanylin were quantified by real-time PCR. Liver morphology, and hepatocyte necrosis, apoptosis and proliferation, were examined at 1-3 days post-injury in mice on a mixed genetic background. Survival was followed for 14 days after carbon tetrachloride injection in wild type and GC-C deficient mice on both a mixed genetic background and on an inbred C57BL6/J background.
GC-C deficient mice on the mixed genetic background nearly all died (median survival of 5 days) following carbon tetrachloride injection while WT littermates experienced only 35% mortality. Elevated levels of TUNEL-positive hepatocyte death on post-injury day 1, increased apoptosis on day 2, and increased areas of centrilobular necrosis on days 2 and 3, were evident in livers from GC-C null mice compared to WT. Collectively these data suggest increased hepatocyte death in the GC-C null mice in the early time period after injury. This corresponds temporally with increased expression of GC-C and its ligands guanylin and uroguanylin in post-injury WT mouse liver. The hepatocyte proliferative response to injury was the same in both genotypes. In contrast, there was no difference in survival between GC-C null and WT mice on the inbred C57BL/6 J background in response to acute liver injury.
Signalling via GC-C promotes hepatocyte survival in vivo and is required for effective recovery from acute toxic injury to the liver in a strain-specific manner.
The family of particulate guanylate cyclases (GC) is known to play substantial roles in the function of a number of different organs. These membrane receptors include the natriuretic peptide receptors GC-A and GC-B in the cardiovascular system, and GC-E and GC-F in the retinal phototransduction system (reviewed in ). GC-C is most highly expressed in the intestine where it is the receptor for the peptides guanylin (Gn) and uroguanylin (Ugn) and contributes to the maintenance of fluid and salt homeostasis via ligand-activated cGMP production. Activation of this receptor by the bacterial heat-stable enterotoxin, which is very similar in sequence and structure to the mammalian peptides Gn and Ugn, results in secretory diarrhea in both animals and man and is a major health problem. Recent advances in our understanding of GC-C mediated signaling in intestinal epithelial cells have suggested a role in basic cellular processes including apoptosis and proliferation ([5–9].
While highest in the intestine, GC-C expression is also found in other tissues including kidney, pancreas, and liver. Similar to its expression in the intestine, GC-C is temporally regulated in the liver of rodents and is expressed at highest levels in the perinatal period [12, 13]. In the adult liver, GC-C expression is undetectable (by Northern analysis) but is up-regulated in injury/regeneration models, including exposure to the hepatotoxin CCl4 and by partial hepatectomy [14, 15]. In mice with a deficiency of GC-C the liver appears normal and no phenotype has been described under specific-pathogen free husbandry[16, 17].
Administration of CCl4 is a widely used model of necroinflammatory liver injury and regeneration. In centrilobular hepatocytes of the liver, cytochrome P450 enzymes mediate metabolism of CCl4 into toxic free radicals which cause lipid peroxidation and membrane damage, eventually resulting in necrosis . Hepatocyte death due to apoptosis via activation of caspase 3, although not as prominent as death due to necrosis, has also been demonstrated to play a role in CCl4 injury [19–22]. Proliferation of surviving hepatocytes, along with removal of cellular debris and restoration of the extracellular matrix, ultimately results in liver regeneration . In order to explore the role of GC-C in the liver, we compared the response of wild type (WT) and GC-C null mice to acute CCl4 injury.
GC-C knock out (KO) mice with a targeted disruption of the Gucy2c gene  were maintained on a C57BL/6J background, following 10 backcross generations. Where indicated, these G-CC null mice were crossed with Black Swiss outbred mice (NTac:NIHBS, Taconic, Hudson, NY) and the resulting heterozygous mice mated to generate homozygous wild type (WT) controls and GC-C null littermates (F2 generation). All mice were genotyped by PCR. Mice were housed under specific-pathogen free conditions and fed food and water ad libitum. Adult mice of both sexes, aged 8-12 weeks, were used in experiments. Animal protocols were approved by the Institutional Animal Care and Use Committee of the Cincinnati Children's Hospital Medical Center (Cincinnati, OH).
Acute Liver Injury
Mice were exposed to a single intraperitoneal injection of CCl4 (Sigma-Aldrich, St. Louis, MO) at a dose of 1 μl CCl4 per gram body weight as a 50% solution in corn oil. Vehicle control mice were injected with corn oil alone. Injections were performed within a 2 hr window to minimize any variation due to circadian rhythm. Mice were examined daily and sacrificed at the indicated times. The liver was excised, weighed, and divided into aliquots which were snap-frozen for later analysis, or fixed in formalin. After paraffin embedding, sections were either stained with hematoxylin and eosin for light microscopic analysis or reserved for immunohistochemistry.
DNA fragmentation was examined using TUNEL staining as described . Briefly, tissue sections were digested with Proteinase K, and then incubated in freshly made reaction buffer containing terminal transferase and biotin-16-dUTP (Roche Diagnostic, Indianapolis, IN) to end-label DNA fragments. Labeled DNA was detected using the Vectastain ABC-alkaline phosphatase system (Vector Laboratories, Burlingame, CA) and Sigma Fast Red (Sigma-Aldrich). As a negative control, terminal transferase was omitted from the reaction buffer. To measure hepatocyte death at 24 hours post- CCl4 injection, the number of labeled nuclei present in 3 high-power fields per liver was counted by an investigator unaware of the mouse genotype. Intense staining of necrotic areas at later time points prevented similar analyses. Instead, the area of necrotic damage compared to the total area of the field, excluding blood vessels and ducts, was determined using ImageJ version 1.38 (National Institutes of Health, Bethesda, MD), and a percentage of necrotic damage was calculated for each liver sample.
Paraffin-embedded liver sections were stained with antibody against activated caspase 3 (1:250 dilution, Cleaved Caspase 3 (Asp175) Antibody, Cell Signaling Technology, Inc., Danvers, MA) and counterstained with hematoxylin as described . To quantify, cleaved caspase 3 -positive cells were counted in 10 randomly selected fields per mouse liver (200× magnification) by an investigator unaware of the genotype. Caspase 3 activity was measured using a colorimetric substrate (Ac-DEVD-pNA, Enzo Life Sciences, Plymouth Meeting, PA). An aliquot of frozen liver was homogenized in lysis buffer containing 50 mM HEPES, pH 7.4, 5 mM CHAPS, and 5 mM DTT, and centrifuged at 20,000 × g for 30 min at 4°C. Cytosolic protein (100 μg as determined by the Bradford assay, Bio-Rad, Hercules, CA) was incubated overnight at 37°C with 20 mM Ac-DEVD-pNA in assay buffer (20 mM HEPES, pH 7.4, 2 mM EDTA, 0.1% CHAPS, and 5 mM DTT). The amount of pNA released from the substrate was measured by determining the absorbance value at 405 nm. The activity in control livers from mice injected with vehicle alone did not differ between genotypes so the combined average value was used for normalization.
Proliferating cell nuclear antigen (PCNA) staining was used as a marker for hepatocyte proliferation that occurs in response to CCl4 injury. Tissue sections were deparaffinized, rehydrated and endogenous peroxidase activity quenched with 1% hydrogen peroxide for 15 min. After washing, tissues were heated in 0.01 M sodium citrate, pH 6, to promote antigen exposure. Sections were then washed, blocked in 3% normal goat serum, and incubated with PCNA polyclonal antibody (1:500, Santa Cruz Biotechnology, Santa Cruz, CA) overnight at 4°C. Following washes, sections were incubated with biotinylated anti-rabbit secondary antibody and labeled nuclei detected using the Vectastain ABC-horseradish peroxidase kit and 3,3-diaminobenzidine (Vector Laboratories). Sections were counterstained with hematoxylin (Fisher Scientific, Pittsburgh, PA). As a negative control, primary antibody was omitted. For each tissue, the hepatocyte labeling index (percent of nuclei that stain positive for PCNA) was determined. Both PCNA-labeled and unlabeled hepatocyte nuclei were counted in 3 high-power fields (≥ 1100 nuclei per tissue) in a blinded fashion.
Quantitative Real-Time PCR
Total RNA was isolated from frozen liver using Tri Reagent (Molecular Research Center, Inc., Cincinnati, OH) according to the manufacturer's protocol. RNA samples were treated with DNase I (DNA-free, Ambion, Austin, TX) and reverse-transcribed (2 μg) using random decamers (RETROscript, Ambion). PCR reactions using specific gene primers were performed with Brilliant II SYBR Green QPCR mix (Stratagene, La Jolla, CA) in the Mx3000p thermocycler (Stratagene). A relative amount for each gene examined was obtained from a standard curve generated by plotting the cycle threshold value against the concentration of a serially diluted RNA sample expressing the gene of interest. This amount was normalized to the level of 18 S RNA, which did not vary with CCl4 treatment. Primer sequences used were as follows: GCC, forward 5'-CGAAAGCGCCTGCGTGAAGC and reverse 5'-TTCACAGGTGCTGCTCCGGC; 18 S, forward 5'-GATCCGAGGGCCTCACTAAAC and reverse 5'-AGTCCCTGCCCTTTGTACACA; Ugn, forward 5'-TGAGTTGGAGGAGAAGGAGATGTC and reverse 5'-AAGGGCAAGGCTGGGTTATG; Gn, forward 5'-GAGTGACATCGCTTGCCTTTC and reverse 5'-TGAGTTTGTTAGCCTCGTGACTTC; and Cyp2e1, forward 5'-TCAAAAAGACCAAAGGCCAGC and reverse 5'-TCCGCAATGACATTGCAGG .
Kaplan-Meier survival curves were generated for each genotype and the log-rank test used for comparison (Prism, GraphPad, San Diego, CA). The Mann-Whitney test was used to evaluate the statistical significance between 2 groups (Prism). A P value less than or equal to 0.05 was considered significant.
Decreased survival of GC-C deficient mice following liver injury is strain-specific
We asked whether GC-C signaling was also a factor in survival of mice on the inbred C57BL/6 background (> 10 backcross generations). As shown in Figure 1B, there was no significant difference in survival between GC-C null and WT mice (58% vs. 75%) on the inbred background. Therefore, the protective role of GC-C in liver injury is strain-specific. We utilized mice of mixed genetic background to further characterize the role of GC-C in our subsequent studies since they demonstrated a profound difference in survival.
Comparison of hepatocyte death in WT and GC-C null mice
Hepatocyte proliferation is normal in GC-C null mice
This study demonstrates that GC-C, known primarily for its role in intestinal epithelial cell function, also plays an important role in the response to liver injury. GC-C null mice do not survive the acute liver injury mediated by a dose of CCl4 that causes 35% lethality in WT mice. The median length of survival is 5 days with almost all GC-C KO mice succumbing by post-injury day 9.
There was no effect on survival in GC-C deficient mice on the C57Bl/6J inbred background following toxic liver injury (Figure 3). Strain-specific differences in the phenotype of gene mutations are found in the literature, especially in the study of multigenic diseases such as cancer and diabetes . For example, the C57BL/6J strain is known to be resistant to liver tumorigenesis in response to the chemical diethylnitrosamine and thus was used to elucidate the role of p27Kip1 as a tumor suppressor . This strain is also resistant to liver fibrosis following chronic CCl4 administration, most probably due to a predominantly Th1 cytokine response compared to a Th2 response in susceptible strains . At this time the C57BL/6J-specific factors that are responsible for the successful recovery of GC-C KO mice after liver injury have not been identified. Our use of the outbred Black Swiss mouse was crucial in uncovering the lack of survival following liver injury in the GC-C KO  that was not seen on the C57Bl/6J inbred background. However, the concomitant individual variability also complicates the study of the mechanism (s) of GC-C action. We focused our research on comparing the early hallmarks of hepatocyte apoptosis/necrosis and subsequent proliferation in both genotypes. Possible causes of deaths occurring later in the regeneration process have not been explored.
GC-C has been localized to non-parenchymal cells and hepatocytes [15, 31] and although the cellular localization of Gn and Ugn is not known their detection and increased expression following CCl4 exposure (Figure 1) is consistent with a role for the GC-C receptor signalling system during liver repair. In addition, both Gn [32, 33]and Ugn [34, 35]are known to circulate in the plasma. In response to CCl4 injury GC-C expression is also up-regulated in the mouse liver, as has previously been shown in rats . In primary rat hepatocyte cultures, the addition of glucocorticoids and IL-6 , and both insulin and heregulin-β1, have been shown to increase GC-C levels. Therefore, we speculate that IL-6 , a key coordinator in the response to liver injury, plays a role in mediating the increased expression of GC-C that we and others have observed.
While the level of hepatocyte proliferation after injury is comparable to WT (Figure 8), GC-C deficiency results in increased hepatocyte cell death (4 times the level in WT liver) 1 day after CCl4 administration, as well as an increased extent of necrotic areas at later time points (Figures 4 & 6). Our Caspase 3 studies (Figure 7) demonstrate that increased apoptosis also contributes to the overall increased hepatocyte death in GC-C null mice. This suggests that the mortality that occurs within a few days of injury may be due to an imbalance in the rates of hepatocyte loss and repopulation. Increased levels of apoptosis have been demonstrated in GC-C KO intestine in a non-lethal radiation model and appear to be mediated by a cGMP-dependent mechanism  while one study also demonstrated an increase in crypt cell apoptosis in the GC-C KO intestine at baseline compared to WT mice . It is not known if the protective mechanisms of GC-C signalling in the intestine and liver are similar and further exploration is warranted.
Lack of GC-C expression in outbred mice versus inbred C57BL6/J mice revealed a strain-specific protective role for GC-C in the liver following acute CCl4 injury. In contrast to WT littermates, GC-C null mice exhibited near 100% lethality. Increased hepatocyte cell death due to both necrosis and apoptosis occurred in the days immediately following exposure in the GC-C KO mice and likely contributed to mortality.
This work was supported by NIH grant R01 DK-47318 (M.B.C.) and by PHS Grant P30 DK078392. We thank Jennifer A. Hawkins and Eleana Harmel-Laws for technical expertise.
- Lucas KA, Pitari GM, Kazerounian S, Ruiz-Stewart I, Park J, Schulz S, Chepenik KP, Waldman SA: Guanylyl cyclases and signaling by cyclic GMP. Pharmacol Rev. 2000, 52 (3): 375-414.PubMedGoogle Scholar
- Currie MG, Fok KF, Kato J, Moore RJ, Hamra FK, Duffin KL, Smith CE: Guanylin: an endogenous activator of intestinal guanylate cyclase. Proc Natl Acad Sci USA. 1992, 89 (3): 947-951. 10.1073/pnas.89.3.947.View ArticlePubMedPubMed CentralGoogle Scholar
- Hamra FK, Forte LR, Eber SL, Pidhorodeckyj NV, Krause WJ, Freeman RH, Chin DT, Tompkins JA, Fok KF, Smith CE, Duffin KL, Siegel NR, Currie MG: Uroguanylin: structure and activity of a second endogenous peptide that stimulates intestinal guanylate cyclase. Proc Natl Acad Sci USA. 1993, 90 (22): 10464-10468. 10.1073/pnas.90.22.10464.View ArticlePubMedPubMed CentralGoogle Scholar
- Schulz S, Green CK, Yuen PS, Garbers DL: Guanylyl cyclase is a heat-stable enterotoxin receptor. Cell. 1990, 63 (5): 941-948. 10.1016/0092-8674(90)90497-3.View ArticlePubMedGoogle Scholar
- Garin-Laflam MP, Steinbrecher KA, Rudolph JA, Mao J, Cohen MB: Activation of guanylate cyclase C signaling pathway protects intestinal epithelial cells from acute radiation-induced apoptosis. Am J Physiol. 2009, 296 (4): G740-749.Google Scholar
- Li P, Lin JE, Chervoneva I, Schulz S, Waldman SA, Pitari GM: Homeostatic control of the crypt-villus axis by the bacterial enterotoxin receptor guanylyl cyclase C restricts the proliferating compartment in intestine. Am J Pathol. 2007, 171 (6): 1847-1858. 10.2353/ajpath.2007.070198.View ArticlePubMedPubMed CentralGoogle Scholar
- Pitari GM, Di Guglielmo MD, Park J, Schulz S, Waldman SA: Guanylyl cyclase C agonists regulate progression through the cell cycle of human colon carcinoma cells. Proc Natl Acad Sci USA. 2001, 98 (14): 7846-7851. 10.1073/pnas.141124698.View ArticlePubMedPubMed CentralGoogle Scholar
- Shailubhai K, Yu HH, Karunanandaa K, Wang JY, Eber SL, Wang Y, Joo NS, Kim HD, Miedema BW, Abbas SZ, Boddupalli SS, Currie MG, Forte LR: Uroguanylin treatment suppresses polyp formation in the Apc(Min/+) mouse and induces apoptosis in human colon adenocarcinoma cells via cyclic GMP. Cancer Res. 2000, 60 (18): 5151-5157.PubMedGoogle Scholar
- Steinbrecher KA, Wowk SA, Rudolph JA, Witte DP, Cohen MB: Targeted inactivation of the mouse guanylin gene results in altered dynamics of colonic epithelial proliferation. Am J Pathol. 2002, 161 (6): 2169-2178.View ArticlePubMedPubMed CentralGoogle Scholar
- Sindice A, Basoglu C, Cerci A, Hirsch JR, Potthast R, Kuhn M, Ghanekar Y, Visweswariah SS, Schlatter E: Guanylin, uroguanylin, and heat-stable euterotoxin activate guanylate cyclase C and/or a pertussis toxin-sensitive G protein in human proximal tubule cells. J Biol Chem. 2002, 277 (20): 17758-17764. 10.1074/jbc.M110627200.View ArticlePubMedGoogle Scholar
- Kulaksiz H, Cetin Y: Uroguanylin and guanylate cyclase C in the human pancreas: expression and mutuality of ligand/receptor localization as indicators of intercellular paracrine signaling pathways. J Endocrinol. 2001, 170 (1): 267-275. 10.1677/joe.0.1700267.View ArticlePubMedGoogle Scholar
- Laney DW, Mann EA, Dellon SC, Perkins DR, Giannella RA, Cohen MB: Novel sites for expression of an Escherichia coli heat-stable enterotoxin receptor in the developing rat. Am J Physiol. 1992, 263 (5 Pt 1): G816-821.PubMedGoogle Scholar
- Swenson ES, Mann EA, Jump ML, Witte DP, Giannella RA: The guanylin/STa receptor is expressed in crypts and apical epithelium throughout the mouse intestine. Biochem Biophys Res Comm. 1996, 225 (3): 1009-1014. 10.1006/bbrc.1996.1286.View ArticlePubMedGoogle Scholar
- Laney DW, Bezerra JA, Kosiba JL, Degen SJ, Cohen MB: Upregulation of Escherichia coli heat-stable enterotoxin receptor in regenerating rat liver. Am J Physiol. 1994, 266 (5 Pt 1): G899-906.PubMedGoogle Scholar
- Scheving LA, Russell WE: Guanylyl cyclase C is up-regulated by nonparenchymal cells and hepatocytes in regenerating rat liver. Cancer Res. 1996, 56 (22): 5186-5191.PubMedGoogle Scholar
- Mann EA, Jump ML, Wu J, Yee E, Giannella RA: Mice lacking the guanylyl cyclase C receptor are resistant to STa-induced intestinal secretion. Biochem Biophys Res Comm. 1997, 239 (2): 463-466. 10.1006/bbrc.1997.7487.View ArticlePubMedGoogle Scholar
- Schulz S, Lopez MJ, Kuhn M, Garbers DL: Disruption of the guanylyl cyclase-C gene leads to a paradoxical phenotype of viable but heat-stable enterotoxin-resistant mice. J Clin Invest. 1997, 100 (6): 1590-1595. 10.1172/JCI119683.View ArticlePubMedPubMed CentralGoogle Scholar
- Recknagel RO, Glende EA, Dolak JA, Waller RL: Mechanisms of carbon tetrachloride toxicity. Pharmacol Ther. 1989, 43: 139-154. 10.1016/0163-7258(89)90050-8.View ArticlePubMedGoogle Scholar
- Kovalovich K, DeAngelis RA, Li W, Furth EE, Ciliberto G, Taub R: Increased toxin-induced liver injury and fibrosis in interleukin-6-deficient mice. Hepatology. 2000, 31 (1): 149-159. 10.1002/hep.510310123.View ArticlePubMedGoogle Scholar
- Kwon YH, Jovanovic A, Serfas MS, Tyner AL: The Cdk inhibitor p21 is required for necrosis, but it inhibits apoptosis following toxin-induced liver injury. J Biol Chem. 2003, 278: 30348-30355. 10.1074/jbc.M300996200.View ArticlePubMedGoogle Scholar
- Shi J, Aisaki K, Ikawa Y, Wake K: Evidence of hepatocyte apoptosis in rat liver after the administration of carbon tetrachloride. Am J Pathol. 1998, 153: 515-525.View ArticlePubMedPubMed CentralGoogle Scholar
- Weber LWD, Boll M, Stampfl A: Hepatotoxicity and mechanism of action of haloalkanes: Carbon tetrachloride as a toxological model. Crit Rev Toxicol. 2003, 33 (2): 105-136. 10.1080/713611034.View ArticlePubMedGoogle Scholar
- Michalopoulos GK, DeFrances MC: Liver regeneration. Science. 1997, 276 (5309): 60-66. 10.1126/science.276.5309.60.View ArticlePubMedGoogle Scholar
- Chen P, Li C, Pang W, Zhao Y, Dong W, Wang S, Zhang J: The protective role of Per2 against carbon tetrachloride-induced hepatotoxicity. Am J Pathol. 2009, 174 (1): 63-70. 10.2353/ajpath.2009.080430.View ArticlePubMedPubMed CentralGoogle Scholar
- Giannella RA, Mann EA: E. coli heat-stable enterotoxin and guanylyl cyclase C: new functions and unsuspected actions. Trans Am Clinic Climatol Assoc. 2003, 114: 67-85.Google Scholar
- Bezerra JA, Currier AR: Plasminogen activators direct reorganization of the liver lobule after acute injury. Am J Pathol. 2001, 158: 921-929.View ArticlePubMedPubMed CentralGoogle Scholar
- Shanmukhappa K, Sabla GE, Degen JL, Bezerra JA: Urokinase-type plasminogen activator supports liver repair independent of its cellular receptor. BMC Gastroenterology. 2006, 6: 40-10.1186/1471-230X-6-40.View ArticlePubMedPubMed CentralGoogle Scholar
- Montagutelli X: Effect of the genetic background on the phenotype of mouse mutations. J Am Soc Nephrol. 2000, 11 (Suppl 16): S101-105.PubMedGoogle Scholar
- Sun D, Ren H, Oertel M, Sellers RS, Shafritz DA, Zhu L: Inactivation of p27Kip1 promotes chemical mouse liver tumorigenesis in the resistant strain C57BL/6J. Mol Carcinogen. 2008, 47 (1): 47-55. 10.1002/mc.20360.View ArticleGoogle Scholar
- Shi Z, Wakil AE, Rockey DC: Strain-specific differences in mouse hepatic wound healing are mediated by divergent T helper cytokine responses. Proc Natl Acad Sci USA. 1997, 94 (20): 10663-10668. 10.1073/pnas.94.20.10663.View ArticlePubMedPubMed CentralGoogle Scholar
- Balint JP, Kosiba JL, Cohen MB: The heat-stable enterotoxin-guanylin receptor is expressed in rat hepatocytes and in a rat hepatoma (H-35) cell line. J Recept Signal Transduc Res. 1997, 17 (4): 609-630. 10.3109/10799899709039153.View ArticleGoogle Scholar
- Kuhn M, Raida M, Adermann K, Schulz-Knappe P, Gerzer R, Heim JM, Forssmann WG: The circulating bioactive form of human guanylin is a high molecular weight peptide (10.3 kDa). FEBS Lett. 1993, 318 (2): 205-209. 10.1016/0014-5793(93)80022-M.View ArticlePubMedGoogle Scholar
- Nakazato M, Yamaguchi H, Shiomi K, Date Y, Fujimoto S, Kangawa K, Matsuo H, Matsukura S: Identification of 10-kDa proguanylin as a major guanylin molecule in human intestine and plasma and its increase in renal insufficiency. Biochem Biophys Res Comm. 1994, 205 (3): 1966-1975. 10.1006/bbrc.1994.2901.View ArticlePubMedGoogle Scholar
- Hess R, Kuhn M, Schulz-Knappe P, Raida M, Fuchs M, Klodt J, Adermann K, Kaever V, Cetin Y, Forssmann WG: GCAP-II: isolation and characterization of the circulating form of human uroguanylin. FEBS Lett. 1995, 374 (1): 34-38. 10.1016/0014-5793(95)01075-P.View ArticlePubMedGoogle Scholar
- Kinoshita H, Nakazato M, Yamaguchi H, Matsukura S, Fujimoto S, Eto T: Increased plasma guanylin levels in patients with impaired renal function. Clinic Nephrol. 1997, 47 (1): 28-32.Google Scholar
- Scheving LA, Russell WE: Insulin and heregulin-beta1 upregulate guanylyl cyclase C expression in rat hepatocytes: reversal by phosphodiesterase-3 inhibition. Cell Signal. 2001, 13 (9): 665-672. 10.1016/S0898-6568(01)00179-6.View ArticlePubMedGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-230X/10/86/prepub
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.