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P C Simpson

Publications and source records attributed to P C Simpson.

At least 19 recordsLinked to original sources
PubMed2000

Autonomous and growth factor-induced hypertrophy in cultured neonatal mouse cardiac myocytes. Comparison with rat.

Cultured neonatal rat cardiac myocytes have been used extensively to study cellular and molecular mechanisms of cardiac hypertrophy. However, there are only a few studies in cultured mouse myocytes despite the increasing use of genetically engineered mouse models of cardiac hypertrophy. Therefore, we characterized hypertrophic responses in low-density, serum-free cultures of neonatal mouse cardiac myocytes and compared them with rat myocytes. In mouse myocyte cultures, triiodothyronine (T3), norepinephrine (NE) through a beta-adrenergic receptor, and leukemia inhibitory factor induced hypertrophy by a 20% to 30% increase in [(3)H]phenylalanine-labeled protein content. T3 and NE also increased alpha-myosin heavy chain (MyHC) mRNA and reduced beta-MyHC. In contrast, hypertrophic stimuli in rat myocytes, including alpha(1)-adrenergic agonists, endothelin-1, prostaglandin F(2alpha), interleukin 1beta, and phorbol 12-myristate 13-acetate (PMA), had no effect on mouse myocyte protein content. In further contrast with the rat, none of these agents increased atrial natriuretic factor or beta-MyHC mRNAs. Acute PMA signaling was intact by extracellular signal-regulated kinase (ERK1/2) and immediate-early gene (fos/jun) activation. Remarkably, mouse but not rat myocytes had hypertrophy in the absence of added growth factors, with increases in cell area, protein content, and the mRNAs for atrial natriuretic factor and beta-MyHC. We conclude that mouse myocytes have a unique autonomous hypertrophy. On this background, T3, NE, and leukemia inhibitory factor activate hypertrophy with different mRNA phenotypes, but certain Gq- and protein kinase C-coupled agonists do not.

Adrenergic alpha-Agonists↗
PubMed2000

Turn geometry for minimizing band broadening in microfabricated capillary electrophoresis channels.

Turns in microfabricated capillary electrophoresis channels generally result in degraded separation quality. To circumvent this limitation, channels were constructed with different types of turns to determine the design that minimizes turn-induced band broadening. In particular, tapered turns were created by narrowing the separation channel width before the start of a turn and widening the channel after the turn is complete. The radius of curvature of the turn, the length over which the channel is tapered, and the degree of tapering were explored. The column efficiencies were determined by examining the resolution of the 271/281 base pair doublet in the separation of a phiX174 HaeIII DNA sizing ladder. Tapered turns with the smallest radius of curvature (250 microm), the shortest tapering length between the separation and turn widths (55 microm), and the largest tapering ratio (4:1 separation channel width to turn channel width) produced the highest resolution separations. These results are discussed by comparison to theoretical predictions of the effect of tapers and turns on analyte band dispersion in capillary electrophoresis.

Bacteriophage phi X 174↗
PubMed1999

Radial capillary array electrophoresis microplate and scanner for high-performance nucleic acid analysis.

The design, fabrication, and operation of a radial capillary array electrophoresis microplate and scanner for high-throughput DNA analysis is presented. The microplate consists of a central common anode reservoir coupled to 96 separate microfabricated separation channels connected to sample injectors on the perimeter of the 10-cm-diameter wafer. Detection is accomplished by a laser-excited rotary confocal scanner with four color detection channels. Loading of 96 samples in parallel is achieved using a pressurized capillary array system. High-quality separations of 96 pBR322 restriction digest samples are achieved in < 120 s with the microplate system. The practical utility and multicolor detection capability is demonstrated by analyzing 96 methylenetetrahydrofolate reductase (MTHFR) alleles in parallel using a noncovalent 2-color staining method. This work establishes the feasibility of performing high-throughput genotyping separations with capillary array electrophoresis microplates.

Electrophoresis, Capillary↗
PubMed1998

High-throughput genetic analysis using microfabricated 96-sample capillary array electrophoresis microplates.

Capillary array electrophoresis (CAE) microplates that can analyze 96 samples in less than 8 min have been produced by bonding 10-cm-diameter micromachined glass wafers to form a glass sandwich structure. The microplate has 96 sample wells and 48 separation channels with an injection unit that permits the serial analysis of two different samples on each capillary. An elastomer sheet with an 8 by 12 array of holes is placed on top of the glass sandwich structure to define the sample wells. Samples are addressed with an electrode array that makes up the third layer of the assembly. Detection of all lanes with high temporal resolution was achieved by using a laser-excited confocal fluorescence scanner. To demonstrate the functionality of these microplates, electrophoretic separation and fluorescence detection of a restriction fragment marker for the diagnosis of hereditary hemochromatosis were performed. CAE microplates will facilitate all types of high-throughput genetic analysis because their high assay speed provides a throughput that is 50 to 100 times greater than that of conventional slab gels.

Capillary Action↗
PubMed1998

Post-infarction heart failure in the rat is associated with distinct alterations in cardiac myocyte molecular phenotype.

The myocardial molecular and cellular responses to hemodynamic and other hypertrophic stimuli have been characterized extensively, but less is known of the alterations in gene expression during the evolution of heart failure following myocardial infarction, and specifically those affecting the cardiac myocytes. Therefore, the present study was undertaken to test the hypothesis that post-infarction heart failure and remodeling in the rat is associated with a distinct myocyte molecular phenotype. To address this question, hemodynamic measurements were performed in vivo; and myocytes isolated from the non-infarcted myocardium 1 day, 1 week, and 6 weeks post-coronary artery ligation in post-infarct rats and sham controls. Myocyte size, mRNA levels for immediate early genes, contractile proteins, and sarcoplasmic reticulum Ca2+-ATPase (SERCA) and phospholamban were assayed by Northern analyses, and SERCA and phospholamban proteins were examined by Western blotting. Hemodynamic evidence of heart failure was present at all post-infarct time points. Myocyte size was increased significantly at 6 weeks. c-myc expression was increased at 1 day and 1 week in the infarcted rats, but returned to baseline by 6 weeks. Atrial natriuretic peptide and VEGF mRNAs were elevated at 1 and 6 weeks. Both beta-myosin heavy chain and skeletal alpha-actin expression were increased at all post-MI time points. In contrast, neither changes in the expression of the calcium-handling proteins (SERCA and phospholamban) were not observed, nor was there a change in TGFbeta1 or TGFbeta3. These results demonstrate that in rats with post-MI heart failure, there was an immediate induction of the fetal/embryonic transcriptional gene program which preceded myocyte hypertrophy and appeared to persist longer than in pressure-overload models. In further contrast to pressure-overload, expression of sarcoplasmic reticulum Ca2+-ATPase and phospholamban, was not altered despite a comparable degree of cellular hypertrophy and more severe hemodynamic decompensation. These findings suggest that there may be important differences in the regulatory mechanisms underlying these two forms of myocardial hypertrophy and heart failure.

Actins↗
PubMed1998

Cytokine expression increases in nonmyocytes from rats with postinfarction heart failure.

Growing evidence suggests that cardiac nonmyocyte cells may play an important regulatory role in the response to myocardial overload and injury via altered expression of paracrine products, such as cytokines and growth factors, but information concerning the cell-specific changes in the expression of these substances in heart-failure models is limited. Therefore, cardiac nonmyocytes were isolated from rats 1 day and 1 and 6 wk after left coronary artery ligation with resulting hemodynamic evidence of heart failure and in sham-operated control animals. mRNAs for tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, transforming growth factors (TGF)-beta1 and TGF-beta3, and type I and type III collagen were measured by Northern analyses. The temporal and quantitative relationships between the expression of these cytokines and collagen and myocyte hypertrophy were determined. mRNA expression of IL-1beta was increased by 1.3-fold at 1 day and 1 wk, and expression of TNF-alpha, IL-1beta, IL-6, TGF-beta1, and TGF-beta3 were increased by 1.4- to 2.1-fold at the 1-wk time point before returning toward baseline at 6 wk. There were significant correlations between the expression of these cytokines and the expression of types I and III collagen, which also peaked at 1 wk. Myocyte hypertrophy was seen first at 6 wk. These observations are consistent with a hypothesis that nonmyocyte cells play a regulatory role in the extracellular matrix changes during postinfarction remodeling and highlight the importance of examining cell-specific changes in gene expression and elucidating the role of cell-to-cell interactions within the myocardium.

Animals↗
PubMed1997

Thyroid hormone improves function and Ca2+ handling in pressure overload hypertrophy. Association with increased sarcoplasmic reticulum Ca2+-ATPase and alpha-myosin heavy chain in rat hearts.

We asked whether thyroid hormone (T4) would improve heart function in left ventricular hypertrophy (LVH) induced by pressure overload (aortic banding). After banding for 10-22 wk, rats were treated with T4 or saline for 10-14 d. Isovolumic LV pressure and cytosolic [Ca2+] (indo-1) were assessed in perfused hearts. Sarcoplasmic reticulum Ca2+-ATPase (SERCA), phospholamban, and alpha- and beta-myosin heavy chain (MHC) proteins were assayed in homogenates of myocytes isolated from the same hearts. Of 14 banded hearts treated with saline, 8 had compensated LVH with normal function (LVHcomp), whereas 6 had abnormal contraction, relaxation, and calcium handling (LVHdecomp). In contrast, banded animals treated with T4 had no myocardial dysfunction; these hearts had increased contractility, and faster relaxation and cytosolic [Ca2+] decline compared with LVHcomp and LVHdecomp. Myocytes from banded hearts treated with T4 were hypertrophied but had increased concentrations of alpha-MHC and SERCA proteins, similar to physiological hypertrophy induced by exercise. Thus thyroid hormone improves LV function and calcium handling in pressure overload hypertrophy, and these beneficial effects are related to changes in myocyte gene expression. Induction of physiological hypertrophy by thyroid hormone-like signaling might be a therapeutic strategy for treating cardiac dysfunction in pathological hypertrophy and heart failure.

Animals↗
PubMed1996

Alpha1-adrenergic receptor subtype mRNAs are differentially regulated by alpha1-adrenergic and other hypertrophic stimuli in cardiac myocytes in culture and in vivo. Repression of alpha1B and alpha1D but induction of alpha1C.

The three cloned alpha1-adrenergic receptor (AR) subtypes, alpha1B, alpha1C, and alpha1D, can all couple to the same effector, phospholipase C, and the reason(s) for conservation of multiple subtypes remain uncertain. All three alpha1-ARs are expressed natively in cultured neonatal rat cardiac myocytes, where chronic exposure to the agonist catecholamine norepinephrine (NE) induces hypertrophic growth and gene transcription. We show here, using RNase protection, that the alpha1-AR subtype mRNAs respond in distinctly different ways during prolonged NE exposure (12 72 h). Alpha1B and alpha1D mRNA levels were repressed by NE, whereas alpha1C mRNA was induced. Changes in mRNA levels were mediated by an alpha1-AR, were not explained by altered mRNA stability, and were reflected in receptor proteins by [3H]prazosin binding. alpha1-AR-stimulated phosphoinositide hydrolysis and myocyte growth were not desensitized. Three other hypertrophic agonists in culture, endothelin-1, PGF2alpha, and phorbol 12-myristate 13-acetate, also induced alpha1C mRNA and repressed alpha1B mRNA. In myocytes from hearts with pressure overload hypertrophy, alpha1 mRNA changes were identical to those produced by NE in culture. These results provide the first example of a difference in regulation among alpha1-AR subtypes expressed natively in the same cell. Transcriptional induction of the alpha1C-AR could be a mechanism for sustained growth signaling through this receptor and is a common feature of a hypertrophic phenotype in cardiac myocytes.

Adrenergic alpha-Agonists↗
PubMed1995

M-CAT, CArG, and Sp1 elements are required for alpha 1-adrenergic induction of the skeletal alpha-actin promoter during cardiac myocyte hypertrophy. Transcriptional enhancer factor-1 and protein kinase C as conserved transducers of the fetal program in cardiac growth.

Induction of the fetal isogenes skeletal alpha-actin (skACT) and beta-myosin heavy chain (beta-MHC) is characteristic of cardiac growth in many models, suggesting a conserved signaling pathway. However, divergent regulation has also been observed. beta-Protein kinase C (PKC) and transcriptional enhancer factor-1 (TEF-1) are involved in induction of beta-MHC in alpha 1-adrenergic-stimulated hypertrophy of cultured cardiac myocytes (Kariya, K., Farrance, I.K. G., and Simpson, P.C. (1993) J. Biol. Chem. 268, 26658-26662; Kariya, K., Karns, L. R., and Simpson, P.C. (1994) J. Biol. Chem. 269, 3775-3782). In the present study, we asked whether the skACT promoter used the same mechanism. A mouse skACT promoter fragment (-113/-46) was induced by both alpha 1-adrenergic stimulation and co-transfection of activated beta-PKC, and contained three required DNA sequence elements: M-CAT, CArG, and Sp1. The skACT M-CAT element bound TEF-1 in cardiac myocytes. Thus the skACT and beta-MHC promoters both require a TEF-1 binding site for activation by alpha 1-adrenergic stimulation, but differ in that skACT also requires a CArG box. These results provide a potential molecular basis for divergent regulation of the fetal program, and also imply that PKC and TEF-1 are conserved transducers for this program during cardiac growth.

Actins↗
PubMed1994

Distribution of alpha 1C-adrenergic receptor mRNA in adult rat tissues by RNase protection assay and comparison with alpha 1B and alpha 1D.

Two alpha 1-adrenergic receptor (AR) subtypes have been defined by pharmacological studies in rat tissues, the alpha 1A and the alpha 1B, whereas three alpha 1-ARs have been cloned, alpha 1B, alpha 1C, and alpha 1D. It has been reported that alpha 1C mRNA is absent in all rat tissues, making uncertain the correspondence of this cloned subtype, if any, to the native alpha 1-ARs defined by pharmacological criteria. In the present study, a partial alpha 1C-AR cDNA was obtained from rat cardiac myocytes using RT-PCR with degenerate primers. A sensitive RNase protection assay was used to map the distribution of alpha 1C mRNA in adult rat tissues, in comparison with alpha 1B and alpha 1D. alpha 1C mRNA was abundant in heart, brain, aorta, vena cava, vas deferens, submaxillary gland, lung, and kidney; was detected at lower levels in prostate, parotid gland, and skeletal muscle; and was undetectable in liver and spleen. alpha 1B and alpha 1D mRNAs were present in most of the same tissues. In contrast to alpha 1C, however, alpha 1B and alpha 1D were both present in spleen; alpha 1B was the sole alpha 1-AR mRNA in liver; and alpha 1D mRNA was not detected in submaxillary gland, a tissue known to be enriched in the pharmacological alpha 1A. We conclude that the distribution of alpha 1C-AR mRNA in rat tissues is compatible with the idea that the alpha 1C corresponds to the classical native alpha 1A-AR. Although many tissues contain all three alpha 1-AR mRNAs, distinct tissue-specific expression is evident.

Amino Acid Sequence↗
PubMed1994

An enhancer core element mediates stimulation of the rat beta-myosin heavy chain promoter by an alpha 1-adrenergic agonist and activated beta-protein kinase C in hypertrophy of cardiac myocytes.

In hypertrophy of cultured rat cardiac myocytes, alpha 1-adrenergic agonists activate protein kinase C (PKC) and up-regulate beta-myosin heavy chain (MHC). The 3300-base pair (bp) rat beta-MHC promoter is stimulated by both an alpha 1-agonist and a constitutively activated mutant of beta-PKC (Kariya, K., Karns, L. R., Simpson, P. C. (1991) J. Biol. Chem. 266, 10023-10026). Here, we report the convergence of alpha 1-adrenergic and beta-PKC signaling on the same element of the beta-MHC promoter. A 20-bp sequence in the beta-MHC promoter (-215/-196) was required for induction by both alpha 1-adrenergic stimulation and beta-PKC and conferred induction on a heterologous promoter. This sequence bound myocyte nuclear factor(s) through a 9-bp "enhancer core" (5'-TGTGGTATG-3'). A 3-bp mutation within the enhancer core which abolished factor binding also abolished inducibility of a 215-bp beta-MHC promoter. These results support the idea that beta-PKC is in the pathway for alpha 1-adrenergic regulation of beta-MHC transcription during cardiac myocyte hypertrophy. The enhancer core is the first PKC response element mapped by transfection of an activated PKC mutant, rather than by treatment with phorbol esters.

Animals↗
PubMed1994

Cloning of the rat alpha 1C-adrenergic receptor from cardiac myocytes. alpha 1C, alpha 1B, and alpha 1D mRNAs are present in cardiac myocytes but not in cardiac fibroblasts.

alpha 1-Adrenergic receptor (AR) activation in cardiac muscle has several different physiological effects that might be mediated through different alpha 1-AR subtypes. Two alpha 1-AR subtypes have been cloned from the rat, the alpha 1B and the alpha 1D; both are present in adult rat heart. A third subtype, the alpha 1C, cloned from the cow and human, was reported to be absent in the rat. However, we recently found alpha 1C mRNA in adult rat heart by using a partial alpha 1C cDNA. Thus, all three cloned alpha 1-AR subtypes are present in the heart, but it is unknown whether each is expressed in cardiac myocytes or in cardiac fibroblasts. In the present study, the full-length rat alpha 1C-AR was cloned from cultured neonatal cardiac myocytes. alpha 1C mRNA transcripts of 3, 9.5, and 11 kb were present in adult rat heart by Northern blot analysis. alpha 1B-, alpha 1C-, and alpha 1D-subtype mRNAs were each present in isolated adult and neonatal cardiac myocytes by RNase protection assay. In addition, cultured neonatal cardiac myocytes expressed the three alpha 1-AR subtype mRNAs. In contrast, none of the alpha 1-AR mRNAs was detected in cultured neonatal cardiac fibroblasts. In addition, alpha 1-ARs were absent in fibroblasts by [3H]prazosin binding and norepinephrine-stimulated [3H]inositol phosphate production. The absence of alpha 1-ARs in cardiac fibroblasts differs from beta-adrenergic and angiotensin II receptors, which are present in both cardiac fibroblasts and cardiac myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Transcriptional enhancer factor-1 in cardiac myocytes interacts with an alpha 1-adrenergic- and beta-protein kinase C-inducible element in the rat beta-myosin heavy chain promoter.

In cultured rat cardiac myocytes, a 20-base pair sequence (-215/-196) of the rat beta-myosin heavy chain (MHC) promoter mediates induction by both alpha 1-adrenergic stimulation and a constitutively activated beta-protein kinase C (PKC), and binds cardiac myocyte nuclear factor(s) through an "enhancer core" element (5'-TGTGG-TATG-3') (Kariya, K., Karns, L. R., and Simpson, P. C. (1994) J. Biol. Chem. 269, in press). Here, we report identification of this enhancer core binding factor as the rat homologue of transcriptional enhancer factor-1 (TEF-1), a human transcription factor for viral enhancers. In gel mobility shift and immunoblot analyses, the myocyte factor and human TEF-1 were indistinguishable in terms of sequence recognition, mobility, and immunoreactivity. Furthermore, DNA binding activity for the beta-MHC enhancer core and TEF-1 immunoreactivity correlated closely. These results are the first to suggest a role for TEF-1 in transcriptional regulation by PKC. The data also provide direct evidence for interaction of TEF-1 with the beta-MHC promoter, supporting a function for TEF-1 in regulation of cellular gene expression, as well as viral, and outline a pathway for alpha 1-adrenergic regulation of beta-MHC gene transcription in cardiac myocytes.

Animals↗
PubMed1993

Beta-adrenergic stimulation of cardiac non-myocytes augments the growth-promoting activity of non-myocyte conditioned medium.

Although the stimulatory action of catecholamines on the heart has been presumed to result exclusively from their direct effects on the cardiac myocytes, little work has been done addressing the effects of catecholamines on the supporting non-myocytes of the heart. We have recently identified medium conditioned by neonatal rat cardiac non-myocytes (NMC-CM) as the source of a growth-promoting factor which leads to cardiac myocyte hypertrophy in culture, suggesting that these non-myocytes may play an active role in myocardial growth. Since cardiac non-myocytes also contain adrenergic receptors (both alpha and beta) on their cell surface, we asked whether adrenergic stimulation of these non-myocytes could supplement the growth-promoting effect of NMC-CM. While isoproterenol (ISO, 0.2 microM) caused no increase in the per cell content of total protein in the non-myocytes, inclusion of ISO in the medium used in the production of NMC-CM augmented the growth promoting effects of this "ISOCM" over control CM. This increase was not seen with the alpha 1 adrenergic agonist phenylephrine suggesting that the stimulatory effect was specific to the beta-adrenergic receptor. Because TGF beta 3 contains an upstream cAMP Response Element, we wonder whether its expression could respond to the increase in cAMP induced by ISO. Non-myocytes treated over 72 h with ISO expressed increased steady state mRNA levels for TGF beta 3 but not that for the closely related TGF beta 1 over this time period. We believe that this is the first report indicating that a potential mechanism for the observed effects of beta-adrenergic stimulation on myocardial cells in culture and possibly relevant in vivo is the contribution of beta-stimulated factor(s) produced by non-myocytes which act in a paracrine fashion on myocardial cells.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Sympathetic modulation of the cardiac myocyte phenotype: studies with a cell-culture model of myocardial hypertrophy.

Myocardial hypertrophy is the common endpoint of many cardiovascular stimuli such as hypertension, myocardial infarction, valvular disease, and congestive failure. Catecholamines have long been implicated in the pathogenesis of myocardial hypertrophy, however, it is very difficult to sort out catecholamine mechanisms in vivo. We have developed a cell-culture model which excludes hemodynamic effects and allows the assignment of receptor specificity to catecholamine effects. Utilizing this system, we have shown that stimulation of the alpha 1 adrenergic receptor leads to the development of myocardial hypertrophy and results in the selective up-regulation of the fetal/neonatal mRNAs encoding skeletal alpha-actin and beta-MHC, a pattern similar to that seen with hypertrophy in-vivo. Utilizing a co-transfection assay, we have also obtained data that suggest that the beta-PKC isozyme is in a pathway regulating transcription of the beta-MHC isogene. Beta adrenergic stimulation of the cultured cardiac myocytes also results in a modest degree of hypertrophy, however, this effect may be dependent upon myocyte contractile activity and may involve, at least in part, the non-muscle cells present in the culture system.

Animals↗
PubMed1991

Expression of a constitutively activated mutant of the beta-isozyme of protein kinase C in cardiac myocytes stimulates the promoter of the beta-myosin heavy chain isogene.

Cultured neonatal rat cardiac myocytes express at least three isozymes of protein kinase C (PKC), and two PKC isozymes are translocated to different intracellular sites on activation with alpha 1-adrenergic agonists or phorbol myristate acetate. Differential intracellular localization upon activation was compatible with differential function, and we therefore asked whether PKC isozymes had distinct roles in regulating transcription of the cardiac myosin heavy chain (MHC) genes. Cardiac myocytes were transfected with chloramphenicol acetyltransferase reporter plasmids containing the promoters of the beta-MHC or alpha-MHC isogenes. An alpha 1-adrenergic agonist stimulated the beta-MHC promoter by 3-fold but had no effect on the alpha-MHC promoter. This pattern of MHC promoter regulation by an alpha 1 agonist was the same as that found previously for the endogenous MHC mRNAs in this model system. Myocytes were then co-transfected with the beta- or alpha-MHC-chloramphenicol acetyltransferase plasmids and expression plasmids encoding wild-type or constitutively activated mutants of the alpha- and beta-isozymes of PKC. Co-transfection with wild-type alpha-PKC or wild-type beta-PKC did not stimulate the beta-MHC promoter, and none of the expressed PKCs affected the alpha-MHC promoter. However, the constitutively activated mutant of beta-PKC stimulated the beta-MHC promoter by 8-fold, whereas stimulation by the activated alpha-PKC mutant was only 40% as great (3-fold). In contrast, the constitutively activated alpha-PKC and beta-PKC mutants were equally potent in stimulating a reporter plasmid containing AP-1 recognition sequences. All transfected PKCs were expressed equally in the myocytes, as judged by immunofluorescence. These data indicate that transcription of the beta-MHC isogene is stimulated preferentially by beta-PKC in cardiac myocytes and provide direct evidence for differential functions of alpa-PKC and beta-PKC in transcriptional regulation.

Animals↗
PubMed1991

A growth factor for cardiac myocytes is produced by cardiac nonmyocytes.

Cardiac nonmyocytes, primarily fibroblasts, surround cardiac myocytes in vivo. We examined whether nonmyocytes could modulate myocyte growth by production of one or more growth factors. Cardiac myocyte hypertrophic growth was stimulated in cultures with increasing numbers of cardiac nonmyocytes. This effect of nonmyocytes on myocyte size was reproduced by serum-free medium conditioned by the cardiac nonmyocytes. The majority of the nonmyocyte-derived myocyte growth-promoting activity bound to heparin-Sepharose and was eluted with 0.75 M NaCl. Several known polypeptide growth factors found recently in cardiac tissue, namely acidic fibroblast growth factor (aFGF), basic FGF (bFGF), platelet-derived growth factor (PDGF), tumor necrosis factor alpha (TNF alpha), and transforming growth factor beta 1 (TGF beta 1), also caused hypertrophy of cardiac myocytes in a dose-dependent manner. However, the nonmyocyte-derived growth factor (tentatively named NMDGF) could be distinguished from these other growth factors by different heparin-Sepharose binding profiles (TNF alpha, aFGF, bFGF, and TGF beta 1) by neutralizing growth factor-specific antisera (PDGF, TNF alpha, aFGF, bFGF, and TGF beta 1), by the failure of NMDGF to stimulate phosphatidylinositol hydrolysis (PDGF and TGF beta 1), and, finally, by the apparent molecular weight of NMDGF (45-50 kDa). This nonmyocyte-derived heparin-binding growth factor may represent a novel paracrine growth mechanism in myocardium.

Animals↗