RESUMEN
BACKGROUND: Resynthesis of triglycerides in enterocytes of the small intestine plays a critical role in the absorption of dietary fat. Acyl-CoA:monoacylglycerol acyltransferase-2 (MGAT2) is highly expressed in the small intestine and catalyzes the synthesis of diacylglycerol from monoacylglycerol and acyl-CoA. To determine the physiological importance of MGAT2 in metabolic disorders and lipid metabolism in the small intestine, we constructed and analyzed Mgat2-deficient mice. RESULTS: In oral fat tolerance test (OFTT), Mgat2-deficient mice absorbed less fat into the circulation. When maintained on a high-fat diet (HFD), Mgat2-deficient mice were protected from HFD-induced obesity and insulin resistance. Heterozygote (Mgat2+/-) mice had an intermediate phenotype between Mgat2+/+ and Mgat2-/- and were partially protected from metabolic disorders. Despite of a decrease in fat absorption in the Mgat2-deficient mice, lipid levels in the feces and small intestine were comparable among the genotypes. Oxygen consumption was increased in the Mgat2-deficient mice when maintained on an HFD. A prominent upregulation of the genes involved in fatty acid oxidation was observed in the duodenum but not in the liver of the Mgat2-deficient mice. CONCLUSION: These results suggest that MGAT2 has a pivotal role in lipid metabolism in the small intestine, and the inhibition of MGAT2 activity may be a promising strategy for the treatment of obesity-related metabolic disorders.
Asunto(s)
Dieta Alta en Grasa/efectos adversos , Grasas/metabolismo , Resistencia a la Insulina/fisiología , Absorción Intestinal/fisiología , Obesidad/metabolismo , Animales , Composición Corporal/genética , Composición Corporal/fisiología , Prueba de Tolerancia a la Glucosa , Resistencia a la Insulina/genética , Absorción Intestinal/genética , Ratones , Ratones Noqueados , N-Acetilglucosaminiltransferasas , Obesidad/genética , Reacción en Cadena de la PolimerasaRESUMEN
BACKGROUND: Neurons and glial cells can be efficiently induced from mouse embryonic stem (ES) cells in a conditioned medium collected from rat primary-cultured astrocytes (P-ACM). However, the use of rodent primary cells for clinical applications may be hampered by limited supply and risk of contamination with xeno-proteins. METHODOLOGY/PRINCIPAL FINDINGS: We have developed an alternative method for unimpeded production of human neurons under xeno-free conditions. Initially, neural stem cells in sphere-like clusters were induced from human ES (hES) cells after being cultured in P-ACM under free-floating conditions. The resultant neural stem cells could circumferentially proliferate under subsequent adhesive culture, and selectively differentiate into neurons or astrocytes by changing the medium to P-ACM or G5, respectively. These hES cell-derived neurons and astrocytes could procure functions similar to those of primary cells. Interestingly, a conditioned medium obtained from the hES cell-derived astrocytes (ES-ACM) could successfully be used to substitute P-ACM for induction of neurons. Neurons made by this method could survive in mice brain after xeno-transplantation. CONCLUSION/SIGNIFICANCE: By inducing astrocytes from hES cells in a chemically defined medium, we could produce human neurons without the use of P-ACM. This self-serving method provides an unlimited source of human neural cells and may facilitate clinical applications of hES cells for neurological diseases.
Asunto(s)
Células Madre Embrionarias/citología , Neuronas/citología , Animales , Secuencia de Bases , Diferenciación Celular , Medios de Cultivo Condicionados , Cartilla de ADN , Electroporación , Humanos , Ratones , Ratas , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Trasplante de Células MadreRESUMEN
Glycoprotein M6A (GPM6A) is known as a transmembrane protein and an abundant cell surface protein on neurons in the central nervous system (CNS). However, the function of GPM6A in the differentiation of neurons derived from human embryonic stem (ES) cells is unknown. To investigate the function of GPM6A in neural differentiation, we generated human ES cell lines with overexpressed (B2h-oeM6A) or suppressed (B2h-shM6A) human GPM6A. Real-time polymerase chain reaction (PCR) showed that overexpression of GPM6A markedly increased the expression of neuroectodermal-associated genes (OTX1, Lmx1b, En1, Pax2, Sox2, and Wnt1), and the number of neural stem cells (NSCs) derived from B2h-oeM6A cells compared to control vector transfected human ES cells (B2h-Mock1). Our results show an increase in the number of differentiated neuronal cells (cholinergic, catecholaminergic, and GABAergic neurons) from NSCs derived from B2h-oeM6A cells. On the other hand, suppression of human GPM6A expression using a short hairpin RNA (shRNA) in human ES cells led to a decrease in both the expression of neuroectodermal-associated genes and the number of NSCs derived from B2h-shM6A cells. In addition, our results show a decrease in the number of differentiated neuronal cells from NSCs in B2h-shM6A cells compared to control vector transfected human ES cells (B2h-shNSP1). Moreover, overexpression or suppression of human GPM6A in human ES cells led to an increase or decrease, respectively, of neuronal migration. Hence, our findings suggest that expression level of GPM6A is, directly or indirectly, associated with the differentiation and neuronal migration of neurons derived from undifferentiated human ES cells.
Asunto(s)
Diferenciación Celular/fisiología , Movimiento Celular/fisiología , Células Madre Embrionarias/fisiología , Glicoproteínas de Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/fisiología , Línea Celular , Células Madre Embrionarias/citología , Técnicas de Silenciamiento del Gen , Humanos , Glicoproteínas de Membrana/genética , Proteínas del Tejido Nervioso/genética , Neuronas/citologíaRESUMEN
Glycoprotein M6A (GPM6A) is known as a transmembrane protein and an abundant cell surface protein on neurons in the central nervous system (CNS). However, the function of GPM6A is still unknown in the differentiation of neurons derived from embryonic stem (ES) cells. To investigate the function of GPM6A, we generated knockdown mouse ES cell lines (D3m-shM6A) using a short hairpin RNA (shRNA) expression vector driven by the U6 small nuclear RNA promoter, which can significantly suppress the expression of mouse GPM6A mRNA. Real-time polymerase chain reaction (real-time PCR) and immunocytochemical analysis showed that expression of shRNA against GPM6A markedly reduced the expression of neuroectodermal-associated genes (OTX1, Lmx1b, En1, Pax2, Pax5, Sox1, Sox2, and Wnt1), and also the number of neural stem cells (NSC) derived from D3mshM6A cells compared to control vector-transfected mouse ES cells (D3m-Mock). Moreover, our results show a decrease in both the number of neuronal markers and the number of differentiating neuronal cells (cholinergic, catecholaminergic, and GABAergic neurons) from NSC in D3m-shM6A cells. Hence, our findings suggest that expression level of GPM6A is directly or indirectly associated with the differentiation of neurons derived from undifferentiated ES cells.
Asunto(s)
Antígenos de Diferenciación/biosíntesis , Diferenciación Celular/fisiología , Células Madre Embrionarias/metabolismo , Regulación de la Expresión Génica/fisiología , Glicoproteínas de Membrana/biosíntesis , Proteínas del Tejido Nervioso/biosíntesis , Neuronas/metabolismo , Animales , Antígenos de Diferenciación/genética , Células COS , Sistema Nervioso Central/citología , Sistema Nervioso Central/metabolismo , Chlorocebus aethiops , Células Madre Embrionarias/citología , Expresión Génica , Glicoproteínas de Membrana/genética , Ratones , Proteínas del Tejido Nervioso/genética , Neuronas/citología , Regiones Promotoras Genéticas/genética , ARN Nuclear Pequeño/genéticaRESUMEN
Excessive salt intake is a major risk factor for hypertension. Here we identify the role of Na(+)/Ca(2+) exchanger type 1 (NCX1) in salt-sensitive hypertension using SEA0400, a specific inhibitor of Ca(2+) entry through NCX1, and genetically engineered mice. SEA0400 lowers arterial blood pressure in salt-dependent hypertensive rat models, but not in other types of hypertensive rats or in normotensive rats. Infusion of SEA0400 into the femoral artery in salt-dependent hypertensive rats increases arterial blood flow, indicating peripheral vasodilation. SEA0400 reverses ouabain-induced cytosolic Ca(2+) elevation and vasoconstriction in arteries. Furthermore, heterozygous NCX1-deficient mice have low salt sensitivity, whereas transgenic mice that specifically express NCX1.3 in smooth muscle are hypersensitive to salt. SEA0400 lowers the blood pressure in salt-dependent hypertensive mice expressing NCX1.3, but not in SEA0400-insensitive NCX1.3 mutants. These findings indicate that salt-sensitive hypertension is triggered by Ca(2+) entry through NCX1 in arterial smooth muscle and suggest that NCX1 inhibitors might be useful therapeutically.
Asunto(s)
Compuestos de Anilina/farmacología , Presión Sanguínea/efectos de los fármacos , Hipertensión/etiología , Músculo Liso Vascular/efectos de los fármacos , Éteres Fenílicos/farmacología , Intercambiador de Sodio-Calcio/metabolismo , Empalme Alternativo/genética , Empalme Alternativo/fisiología , Animales , Calcio/metabolismo , Hipertensión/metabolismo , Immunoblotting , Inmunohistoquímica , Masculino , Arterias Mesentéricas/efectos de los fármacos , Ratones , Ratones Transgénicos , Ouabaína/metabolismo , Ratas , Ratas Sprague-Dawley , Cloruro de Sodio Dietético/metabolismo , Intercambiador de Sodio-Calcio/antagonistas & inhibidores , Vasoconstricción/efectos de los fármacosRESUMEN
Psoriasis is recognized as a chronic inflammatory disease characterized by epidermal hyperproliferation. To identify psoriasis-related genes, we compared the mRNA populations of normal and psoriatic skin. We identified one gene, designated as cornifelin, which showed increased expression in psoriatic skin. Human cornifelin contains 112 amino acids and is expressed in the uterus, cervix, and skin. In situ hybridization analysis demonstrated the presence of human cornifelin in the granular cell layer of the epidermis. To investigate the function of cornifelin, we established a transgenic mouse line overexpressing human cornifelin. Using these mice, we have shown that cornifelin is directly or indirectly cross-linked to at least two other cornified envelope proteins, loricrin and involucrin, in vivo. Overexpression of human cornifelin correlated with decreased loricrin expression and increased involucrin expression in the transgenic mouse. However, abnormality of epidermal differentiation was not observed in the transgenic mouse.
Asunto(s)
Proteínas de la Membrana/biosíntesis , Proteínas de la Membrana/genética , Psoriasis/metabolismo , Piel/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Expresión Génica , Humanos , Inmunohistoquímica , Hibridación in Situ , Queratinas/metabolismo , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Datos de Secuencia Molecular , Precursores de Proteínas/biosíntesis , Precursores de Proteínas/genética , ARN Mensajero/biosíntesis , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homología de Secuencia de Aminoácido , Piel/ultraestructura , Distribución TisularRESUMEN
Psoriasis is a common skin disease characterized by hyperplastic regenerative epidermal growth and infiltration of immunocytes. The etiology of psoriasis is unknown, although several genetic and cellular factors have been elucidated. To find new psoriasis-related genes, we have cloned cDNAs that are differentially expressed between normal and psoriatic skins. Among these clones, we have identified a new gene that codes for a new member of the type IV cytosolic phospholipase A(2) (cPLA(2)) family. We refer to this gene as cPLA(2)delta. It encodes a polypeptide of 818 amino acids that has significant homology with known cPLA(2) proteins in the C2 and catalytic domains. The cPLA(2)delta gene was mapped to the 15q13-14 chromosomal locus, near to the locus of the cPLA(2)beta gene, from which it is separated by a physical distance of about 220 kb. To identify the phospholipase A(2) activity of cPLA(2)delta, we transfected COS-7 cells with His-tagged cPLA(2)delta. The cell lysate from these cells had calcium-dependent phospholipase A(2) activity. Northern blot analysis revealed that a cPLA(2)delta transcript of about 4 kb is expressed in stratified squamous epithelia, such as those in skin and cervix, but not in other tissues. In situ hybridization and immunohistochemistry revealed that cPLA(2)delta is expressed strongly in the upper spinous layer of the psoriatic epidermis, expressed weakly and discontinuously in atopic dermatitis and mycosis fungoides, and not detected in the epidermis of normal skin; cPLA(2)alpha is not detected in either normal or psoriatic skin. These results suggest that cPLA(2)delta exhibits a unique distribution pattern compared with that of known cPLA(2) subtypes, and it may play a critical role in inflammation in psoriatic lesions.
Asunto(s)
Citosol/enzimología , Epitelio/enzimología , Fosfolipasas A/genética , Psoriasis/enzimología , Secuencia de Aminoácidos , Animales , Northern Blotting , Células COS , Calcio/metabolismo , Dominio Catalítico , Mapeo Cromosómico , Cromosomas Humanos Par 15 , Clonación Molecular , ADN Complementario/metabolismo , Dermatitis Atópica/enzimología , Epidermis/enzimología , Humanos , Inmunohistoquímica , Hibridación in Situ , Inflamación/metabolismo , Datos de Secuencia Molecular , Micosis Fungoide/enzimología , Péptidos/química , Fosfolipasas A2 , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Aminoácido , Piel/metabolismo , Distribución Tisular , TransfecciónRESUMEN
We used Na(+)-Ca(2+) exchanger (NCX) knockout mice to evaluate the effects of NCX in cardiac function and the infarct size after ischemia/reperfusion injury. The contractile function in NCX KO mice hearts was significantly better than that in wild type (WT) mice hearts after ischemia/reperfusion and the infarct size was significantly small in NCX KO mice hearts compared with that in WT mice hearts. NCX is critically involved in the development of ischemia/reperfusion-induced myocardial injury and therefore the inhibition of NCX function may contribute to cardioprotection against ischemia/reperfusion injury.
Asunto(s)
Isquemia Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/metabolismo , Intercambiador de Sodio-Calcio/fisiología , Animales , Calcio/química , Calcio/metabolismo , Modelos Animales de Enfermedad , Corazón/fisiopatología , Hemodinámica/fisiología , Heterocigoto , Masculino , Ratones , Ratones Noqueados , Infarto del Miocardio/metabolismo , Daño por Reperfusión Miocárdica/fisiopatología , Miocardio/metabolismo , Miocardio/patología , Miocitos Cardíacos/fisiología , Intercambiador de Sodio-Calcio/genética , Intercambiador de Sodio-Calcio/metabolismo , Coloración y Etiquetado/métodos , Sales de Tetrazolio/químicaRESUMEN
Psoriasis is a skin disease with epidermal keratinocyte hyperproliferation and altered differentiation. To identify novel psoriasis-related genes, we investigated differentially expressed genes between normal and psoriatic skin. We identified a novel acyl CoA:diacylglycerol acyltransferase 2 (DGAT2) gene, which was decreased in human psoriatic skin. DGAT2 mRNA was expressed in sebaceous glands of normal human skin. DGAT2 protein was detected on endoplasmic reticulum. DGAT2 catalyzes the final step in the production of triglycerides and the accumulation of triglycerides in the tissues is considered to be related to insulin resistance. Therefore, we also investigated the expression of the DGAT2 gene in diabetic mice. DGAT2 mRNA was increased in the adipose, small intestine, and skeletal muscle in diabetic mice.
Asunto(s)
Aciltransferasas/metabolismo , Diabetes Mellitus/metabolismo , Psoriasis/metabolismo , Piel/metabolismo , Aciltransferasas/análisis , Aciltransferasas/genética , Animales , Northern Blotting , Diacilglicerol O-Acetiltransferasa , Regulación hacia Abajo , Regulación de la Expresión Génica , Células HeLa , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Psoriasis/genética , Psoriasis/patología , Glándulas Sebáceas/patología , Piel/patologíaRESUMEN
Osteoblast maturation is a multistep series of events characterized by an integrated cascade of gene expression that are accompanied by specific phenotypic alterations. To find new osteoblast-related genes we cloned differentially expressed cDNAs characteristic of specific differentiation stages in the mouse osteoblast-like MC3T3-E1 cells by a differential display method. We identified a novel cDNA encoding a putative glycerophosphodiester phosphodiesterase, GDE3, which specifically was expressed at the stage of matrix maturation. Interestingly, the deduced amino acid sequence contains 539 amino acids including seven putative transmembrane domains and a glycerophosphodiester phosphodiesterase region in one of the extracellular loops. Northern blot analysis revealed that GDE3 was also expressed in spleen as well as primary calvarial osteoblasts and femur. We next transfected HEK293T cells with GDE3 with green fluorescent protein fused to the C terminus. The green fluorescent protein-fused protein accumulated at the cell periphery, and the transfected cells overexpressing the protein changed from a spread form to rounded form with disappearance of actin filaments. Immunofluorescence staining with GDE3 antibody and phalloidin in MC3T3-E1 cells indicated that endogenous GDE3 might be co-localized with the actin cytoskeleton. To identify a role for GDE3 in osteoblast differentiation, MC3T3-E1 cells stably expressing the full-length protein were constructed. Expression of GDE3 showed morphological changes, resulting in dramatic increases in alkaline phosphatase activity and calcium deposit. These results suggest that GDE3 might be a novel seven-transmembrane protein with a GP-PDE-like extracellular motif expressed during the osteoblast differentiation that dramatically accelerates the program of osteoblast differentiation and is involved in the morphological change of cells.
Asunto(s)
Membrana Celular/metabolismo , Osteoblastos/citología , Hidrolasas Diéster Fosfóricas/biosíntesis , Hidrolasas Diéster Fosfóricas/química , Células 3T3 , Fosfatasa Alcalina/metabolismo , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Animales , Northern Blotting , Western Blotting , Diferenciación Celular , Línea Celular , Clonación Molecular , Citoesqueleto/metabolismo , ADN Complementario/metabolismo , Citometría de Flujo , Perfilación de la Expresión Génica , Biblioteca de Genes , Proteínas Fluorescentes Verdes , Humanos , Proteínas Luminiscentes/metabolismo , Ratones , Microscopía Fluorescente , Datos de Secuencia Molecular , Células 3T3 NIH , Plásmidos/metabolismo , Estructura Terciaria de Proteína , Proteínas Recombinantes/metabolismo , Homología de Secuencia de Aminoácido , TransfecciónRESUMEN
The Na(+)/Ca(2+) exchanger (NCX1) plays a key role in maintaining Ca(2+) homeostasis in cardiomyocytes. Disruption of Ncx1 gene in mice results in embryonic lethality between embryonic day 9 and 10, with the mice lacking spontaneous heartbeats. We examined the mechanism of lack of heartbeats in Ncx1-deficient mice. Ultrastructual analysis demonstrated that Ncx1-deficient mice showed severe disorganization of myofibrils, a lack of Z-lines and swelling of mitochondria in cardiomyocytes. However, the expressions of cardiac-specific genes including transcription factor genes and contractile protein genes were not changed in Ncx1-deficient mice. Abnormal Ca(2+) handling itself or the lack of heartbeats due to the inactivation of Ncx1 gene may cause the disorganization of myofibrillogenesis. Although NCX1 protein levels were decreased in heterozygous mice, there were no changes in NCX2 and NCX3 protein levels between wild type and heterozygous mice.
Asunto(s)
Mitocondrias/metabolismo , Miocitos Cardíacos/metabolismo , Miofibrillas/metabolismo , Intercambiador de Sodio-Calcio/fisiología , Animales , Western Blotting , Encéfalo/metabolismo , Células Cultivadas , Embrión de Mamíferos , Regulación de la Expresión Génica , Corazón , Riñón/metabolismo , Ratones , Ratones Noqueados , Mitocondrias/ultraestructura , Miocitos Cardíacos/química , Miocitos Cardíacos/ultraestructura , Miofibrillas/química , Miofibrillas/ultraestructura , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Intercambiador de Sodio-Calcio/análisis , Intercambiador de Sodio-Calcio/genéticaRESUMEN
Using Na+/Ca2+ exchanger (NCX1)-deficient mice, the pathophysiological role of Ca2+ overload via the reverse mode of NCX1 in ischemia/reperfusion-induced renal injury was investigated. Because NCX1(-/-) homozygous mice die of heart failure before birth, we used NCX1(+/-) heterozygous mice. NCX1 protein in the kidney of heterozygous mice decreased to about half of that of wild-type mice. Expression of NCX1 protein in the tubular epithelial cells and Ca2+ influx via NCX1 in renal tubules were markedly attenuated in the heterozygous mice. Ischemia/reperfusion-induced renal dysfunction in heterozygous mice was significantly attenuated compared with cases in wild-type mice. Histological renal damage such as tubular necrosis and proteinaceous casts in tubuli in heterozygous mice were much less than that in wild-type mice. Ca2+ deposition in necrotic tubular epithelium was observed more markedly in wild-type than in heterozygous mice. Increases in renal endothelin-1 content were greater in wild-type than in heterozygous mice, and this reflected the difference in immunohistochemical endothelin-1 localization in necrotic tubular epithelium. When the preischemic treatment with KB-R7943 was performed, the renal functional parameters of both NCX1(+/+) and NCX1(+/-) acute renal failure mice were improved to the same level. These findings strongly support the view that Ca2+ overload via the reverse mode of Na+/Ca2+ exchange, followed by renal endothelin-1 overproduction, plays an important role in the pathogenesis of ischemia/reperfusion-induced renal injury.
Asunto(s)
Enfermedades Renales/metabolismo , Daño por Reperfusión/metabolismo , Intercambiador de Sodio-Calcio/genética , Tiourea/análogos & derivados , Animales , Nitrógeno de la Urea Sanguínea , Western Blotting , Calcio/metabolismo , Células Cultivadas , Endotelina-1/metabolismo , Inmunohistoquímica , Riñón/patología , Enfermedades Renales/genética , Enfermedades Renales/patología , Pruebas de Función Renal , Túbulos Renales Distales/metabolismo , Túbulos Renales Distales/patología , Túbulos Renales Proximales/metabolismo , Túbulos Renales Proximales/patología , Células LLC-PK1 , Masculino , Ratones , Ratones Noqueados , Daño por Reperfusión/genética , Daño por Reperfusión/patología , Intercambiador de Sodio-Calcio/metabolismo , Porcinos , Tiourea/farmacología , Equilibrio Hidroelectrolítico/genética , Equilibrio Hidroelectrolítico/fisiologíaRESUMEN
Using Na(+)/Ca(2+) exchanger (NCX1)-deficient mice, the pathophysiological role of Ca(2+) overload via the reverse mode of the Na(+)/Ca(2+) exchanger in ischaemia/reperfusion-induced renal injury was investigated. Since NCX1(-/-) homozygous mice die of heart failure before birth, we utilized NCX1(+/-) heterozygous mice. The ischaemia/reperfusion-induced renal dysfunction in heterozygous mice were significantly attenuated compared with cases in wild-type mice. Also, histological renal damage such as tubular necrosis and proteinaceous casts in tubuli in heterozygous mice were much less than that in wild-type mice. Ca(2+) deposition in necrotic tubular epithelium was observed more markedly in wild-type than in heterozygous mice. The increase in renal endothelin-1 (ET-1) content was significantly greater in wild-type than in heterozygous mice, and this reflected the difference in immunohistochemical ET-1 localization in necrotic tubular epithelium. We conclude that Ca(2+) overload via the reverse-mode of Na(+)/Ca(2+) exchange, followed by renal ET-1 overproduction, plays an important role in the pathogenesis of ischaemia/reperfusion-induced acute renal failure.
Asunto(s)
Lesión Renal Aguda/etiología , Calcio/metabolismo , Endotelina-1/biosíntesis , Riñón/metabolismo , Daño por Reperfusión/complicaciones , Intercambiador de Sodio-Calcio/metabolismo , Lesión Renal Aguda/metabolismo , Animales , Endotelina-1/análisis , Inmunohistoquímica , Riñón/química , Masculino , Ratones , Ratones Noqueados , Daño por Reperfusión/metabolismo , Intercambiador de Sodio-Calcio/genéticaRESUMEN
The Na+-Ca2+ exchanger (NCX) on the plasma membrane is thought to be the main calcium extrusion system from the cytosol to the extracellular space in many mammalian excitable cells, including cardiac myocytes. However, the pathophysiological role of NCX in the heart is still unclear because of the lack of known specific inhibitors of NCX. To determine the role of NCX in cardiac contraction and the development of cardiac hypertrophy, we imposed pressure overload on the heart of heterozygous NCX knockout (KO) mice by constricting transverse aorta, and examined cardiac function and morphology 3 wk after operation. Although there was no difference in cardiac function between sham-operated KO mice and sham-operated wild-type (WT) mice, KO mice showed higher left ventricular pressure and better systolic function than WT mice in response to pressure overload. Northern blot analysis revealed that mRNA levels of sarcoplasmic reticulum Ca2+-ATPase were reduced by pressure overload in left ventricles of WT but not of KO mice. However, hypertrophic changes with interstitial fibrosis were more prominent in KO mice than WT mice. These results suggest that reduction of NCX results in supernormalized cardiac function and causes marked cardiac hypertrophy in response to pressure overload.