Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study was undertaken to characterize differences in Ca2+ homeostasis between small and large ovine luteal cells. Although increasing extracellular pH (pHex) resulted in increases in intracellular calcium ([Ca2+]in) in both cell types, the large cells exhibited a greater sensitivity, suggesting that distinct [Ca2+]in regulatory mechanisms with distinct pH optima are operating in the two cell types. The sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase inhibitors thapsigargin (TG) and cyclopiazonic acid (CPA) increased [Ca2+]in in both cell types. Treatment of small cells with CPA resulted in transient increases in [Ca2+]in, whereas CPA produced sustained increases in [Ca2+]in in large cells. In small cells, pretreatment with CPA prevented further increases in [Ca2+]in in response to TG and vice versa. In large cells, TG pretreatment precluded further increases in [Ca2+]in with either prostaglandin F2 alpha (PGF2 alpha) or CPA. In contrast, after CPA pretreatment, PGF2 alpha or TG induced further increases in [Ca2+]in in large cells. This suggests that a TG-sensitive, CPA-insensitive Ca2+ pool is present in large cells but not in small cells. Neither Na+ removal nor KCl addition affected [Ca2+]in in either cell type, indicating that neither the Na+/Ca2+ exchanger nor voltage-dependent Ca2+ channels are involved in Ca2+ homeostasis in these cells. Addition of the calcium antagonist, LaCl3 (La3+), produced a gradual increase in [Ca2+]in in large cells but no changes in [Ca2+]in in small cells. Additionally, treatment with increasing concentrations of 4-bromo-A23187 resulted in titratable increases in [Ca2+]in that are greater in large than small cells, suggesting that small cells possess a higher Ca(2+)-buffering capacity than large cells. Progesterone secretion by large cells was significantly inhibited at alkaline pHex. In the presence of PGF2 alpha, progesterone secretion exhibited a distinct pH optimum of 7.0. In contrast, pHex did not affect secretion of progesterone in small cells under any of the conditions tested. TG, CPA, and La3+ all reduced secretion of progesterone in large, but not small, cells. These results demonstrate that ovine large and small luteal cells differ in regulation of [Ca2+]in homeostasis, and that treatments that increase [Ca2+]in decrease progesterone secretion in large cells but have no effect in small cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Differential regulation of Ca2+ homeostasis in ovine large and small luteal cells. 795 33

Cardiac functions are regulated by both contractile proteins and calcium regulatory proteins. In cardiac hypertrophy, an increase in protein synthesis can be partitioned into an increase in both capacity and efficiency of synthesis. beta-cardiac myosin heavy chain (beta-MHC) isoform is predominantly expressed while alpha-MHC is suppressed in pressure overload hypertrophy. The SR Ca(2+)-ATPase is also markedly decreased in pressure overloaded hearts, while in thyrotoxic hearts both are increased. The signal transduction system in cardiac hypertrophy can be examined by stretching cardiac myocytes grown up on deformable membranes. In our analysis, stretching myocytes stimulated protein kinase C, MAP-II kinase and S6 kinase, all of which may lead to the induction of fetal-type cardiac genes and accelerated protein synthesis. Analyses of the subcellular mechanisms of cardiac hypertrophy will provide important insights into understanding of the molecular basis of heart failure.
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PMID:[Molecular basis for heart failure]. 833 89

Cardiac functions are regulated by both contractile proteins and calcium regulatory proteins. Alterations of these are considered involved in impaired contractile and diastolic functions in hypertrophied hearts. In this study, we analyzed molecular changes during the development of cardiac hypertrophy. Cardiac hypertrophy was induced by constricting the pulmonary artery in rabbits or the aorta in rats. In rabbit right ventricular hypertrophy, protein synthesis was increased to 1.8 times the control 2-4 days after pulmonary constriction. This increase in protein synthesis could be classified as an increase in both capacity and efficiency of synthesis. beta-cardiac myosin heavy chain (beta-MHC) isoform was predominantly expressed and alpha-MHC was suppressed in pressure overload hypertrophy. The switch from alpha- to beta-MHC occurred at the mRNA level. Ca(2+)-ATPase of sarcoplasmic reticulum (SR) is important because it regulates intracellular Ca2+ levels during relaxation. In pressure-overload hypertrophy, the SR Ca(2+)-ATPase was markedly decreased in both the enzyme activities and mRNA levels, while in thyrotoxic hearts both were increased. Interstitial cells also undergo phenotypic modulation which was demonstrated by the induction of nonmuscle-type MHC in pressure-overload hypertrophy. The signal transduction system in cardiac hypertrophy was examined by stretching cardiac myocytes grown on deformable membranes. In our analysis, stretching myocytes stimulated protein kinase C, MAP-II kinase and S6 kinase, all of which may lead to the induction of fetal-type cardiac genes and accelerated protein synthesis. These analyses of subcellular adaptation in cardiac hypertrophy provide important insights into understanding molecular mechanisms of cardiac functions.
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PMID:[Molecular basis for cardiac functions]. 835 May 1

The effect of thapsigargin on intracellular free calcium ([Ca2+]i) was examined in swim up human sperm. Thapsigargin elevated [Ca2+]i in a dose dependent manner, with maximal effects observed with 10 microM. The increase in [Ca2+]i was relatively slow in taking 3-4 min to reach a maximal level. The increase in [Ca2+]i was inhibited when extracellular Ca2+ was chelated with EGTA, thus the source of Ca2+ for the increase was extracellular. The effect of thapsigargin to stimulate Ca2+ influx was also observed using the Mn2+ quenching of intracellular Fura-2. Thapsigargin pre-treatment of sperm was able to potentiate the effects of progesterone to elevate [Ca2+]i. Progesterone pre-treatment also potentiated the ability of thapsigargin to elevate [Ca2+]i. Further evidence to support the idea that thapsigargin was promoting Ca2+ influx was the fact that thapsigargin potentiated ionomycin (an agent that can increase Ca2+ cycling across phospholipid membranes) induced elevations in [Ca2+]i. Conversely, ionomycin also potentiated thapsigargin induced elevations in [Ca2+]i. It is concluded from these studies that high concentrations of thapsigargin are able to stimulate Ca2+ influx in human sperm by a mechanism not involving the endoplasmic reticulum Ca(2+)-ATPase pump since this organelle is absent in mature sperm. However, a likely site of action of thapsigargin in mature sperm is at the level of the nuclear membrane Ca(2+)-ATPase pump which is identical to the endoplasmic reticulum Ca(2+)-ATPase pump and is sensitive to inhibition by thapsigargin.
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PMID:Thapsigargin elevates and potentiates the ability of progesterone to increase intracellular free calcium in human sperm: possible role of perinuclear calcium. 838 64

Cyst formation in polycystic kidney disease (PKD) involves proliferation of cyst lining epithelial and changes in trans-epithelial fluid and electrolyte transport. In vitro studies have suggested that mislocation of Na,K-ATPase to the apical tubular surface may be an important component of cyst fluid transport. We undertook in vivo studies of Na,K-ATPase location using the "threshold" murine model of glucocorticoid-induced PKD (GIPKD). Using histological, immunohistochemical, and densitometric techniques, we compared cyst formation and the cellular location of Na,K-ATPase in suckling C3H (low threshold for GIPKD) and DBA (high threshold) mice given an inducing dose of 200 mg/kg methylprednisolone acetate. As expected, C3H mice demonstrated greater cyst formation as measured by proportion of section area occupied by the tubule lumen (26.7% vs 15.5%; p < 0.001). Cyst formation was associated with increased Na,K-ATPase staining and increased apical Na,K-ATPase location. MPA treatment in C3H mice resulted in apical staining that exceeded basolateral staining (35.3% of reference window vs 29.8%; p < 0.001). The relatively GIPKD-resistant DBA mice did not show such change in Na,K-ATPase location. These immunohistochemical studies suggest a role for Na,K-ATPase in renal cyst formation.
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PMID:Renal tubule Na,K-ATPase polarity in glucocorticoid-induced polycystic kidney disease. 838 15

P-glycoprotein (P-gp) is a membranous ATPase responsible for the multidrug resistance (MDR) phenotype. Using membrane vesicles prepared from the highly resistant cell line DC-3F/ADX we studied the influence of P-gp ATPase activity of four progesterone derivatives which specifically bind to P-gp and reverse MDR. Progesterone and desoxycorticosterone stimulate P-gp ATPase activity with, respectively, apparent concentrations giving half-maximal activation of 20-25 microM and 40-50 microM, and activation factors of 2.3 (at 100 microM progesterone) and 1.8 (at 170 microM desoxycorticosterone). Hydrocortisone above 100 microM stimulates P-gp ATPase activity while corticosterone has no apparent stimulating effect. Our data are consistent with the location of the binding sites for the progesterone derivatives on the P-gp membranous domain. The effects of these steroids on verapamil-stimulated P-gp ATPase activity support a non-competitive mechanism, i.e. the binding sites for verapamil and steroids are mutually non-exclusive for P-gp ATPase modulation. A similar non-competitive inhibition of progesterone-stimulated P-gp ATPase activity by desoxycorticosterone or by corticosterone leads to the conclusion that these steroids, although sharing related structures, have distinct modulating sites on P-gp. As expected from their mutually non-exclusive interactions on P-gp, progesterone and verapamil when mixed induce a synergistic modulation of P-gp ATPase activity. Since drug transport by P-gp is believed to be coupled to its ATPase activity, a corresponding synergistic effect of these two modulators for the inhibition of P-gp-mediated drug resistance can be expected.
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PMID:Effects of steroids and verapamil on P-glycoprotein ATPase activity: progesterone, desoxycorticosterone, corticosterone and verapamil are mutually non-exclusive modulators. 871 80

Progesterone is an important regulator of normal and malignant breast epithelial cells. In addition to stimulating development of normal mammary epithelium, it can be used to treat hormone-dependent breast tumors. However, the mechanism of growth inhibition by progestins is poorly understood, and only a limited number of progesterone target genes are known so far. We therefore decided to clone such target genes by means of differential display polymerase chain reaction. In this paper, we describe an improved differential display strategy that eliminates false positives, along with the identification of nine positive (TSC-22, CD-9, Na+/K+-ATPase alpha1, desmoplakin, CD-59, FKBP51, and three unknown genes) and one negative progesterone target genes (annexin-VI) from the mammary carcinoma cell line T47D, which is growth-inhibited by progestins. None of these genes have been reported before to be progesterone targets. Regulation of desmoplakin, CD-9, CD-59, Na+/K+-ATPase alpha1, and annexin-VI by the progestin suggests that progesterone induces T47D cells to differentiate. Three of these genes were repressed by estradiol and up-regulated by the progestin. Estradiol treatment of T47D cells also leads to formation of lamellipodia and delocalization of two cell adhesion proteins, E-cadherin and alpha-catenin. All these effects were reversed by the progestin. These data suggest that estradiol dedifferentiates T47D cells, while progestins have the opposite effect. This may be linked to the capacity of progestins to inhibit tumor growth.
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PMID:Novel progesterone target genes identified by an improved differential display technique suggest that progestin-induced growth inhibition of breast cancer cells coincides with enhancement of differentiation. 919 78

Rats are generally believed to be insensitive for cardiac glycosides. However, like in humans, the hemodynamic effects may be related to the pathophysiological condition. Since the hemodynamic effects of cardiac glycosides have never been investigated in rats with heart failure, the aim of the present experiments was to investigate the role of the pathophysiological condition in the rat. Therefore, hemodynamic and cardiac effects of ouabain were investigated both in normal rats and rats with heart failure due to myocardial infarction (MI). Since the effects of ouabain may also depend on the treatment scheme, rats were treated either for a short-term period or a long-term period. Three weeks after sham surgery or ligation of the left coronary artery (MI), Wistar rats were treated for two weeks with ouabain (14.4 mg/kg.d s.c.), either continuously (osmotic minipumps) or intermittently (once daily). A separate group of rats was treated for 45-60 min (1-100 microg/kg.min ouabain; i.v. infusion 5 weeks after MI). Hemodynamic measurements were performed at rest and after volume loading in conscious rats, chronically instrumented with an electromagnetic flow probe and catheters. Induction of MI resulted in a significant increase in total peripheral resistance (TPR), and a significant decrease in basal and maximal cardiac output following volume loading (basal CO: sham, 92 +/- 5; MI, 74 +/- 5 ml/min; maximal CO: sham, 152 +/- 4; MI, 105 +/- 7 ml/min; n = 7-11). Chronic intermittent ouabain treatment further increased TPR in MI rats. In contrast, continuous ouabain treatment normalized TPR in rats. Only in continuously treated MI rats, basal and maximal CO improved significantly (basal: 83 +/- 4; maximal: 134 +/- 7 ml/min; n = 7). Acute treatment dose-dependently worsened the hemodynamic conditions of MI rats, since TPR and MAP increased and CO and stroke volume decreased significantly. These experiments demonstrate that ouabain can improve cardiac function in rats, although only in MI rats and strongly depending on the delivery regimen. Thus, in contrast to the general belief, the presently used rat model is suitable for investigation of cardiac glycosides in heart failure. The preferential improvement of cardiac function in MI rats continuously treated with ouabain may depend upon changes in Na+,K+-ATPase or altered neurohumoral conditions due to MI and chronic treatment.
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PMID:Ouabain improves cardiac function in vivo in rats with heart failure after chronic but not acute treatment. 927 26

The knowledge about the structure and function of the protein families responsible for cGMP synthesis and metabolic conversion has grown vastly the last years, whereas little is known about proteins that account for the cellular export of cGMP. In the present study, we have employed a model with inside-out vesicles prepared from human erythrocytes to characterize modulation and regulation of cellular cGMP extrusion. The active transport was saturable (Km of 2.4 +/- 0.2 microM, mean +/- SEM, n = 3) and coupled to ATP hydrolysis since no accumulation was detected in the presence of ATP-gamma-S and AMP-PNP. The observation that 100 microM of cAMP caused a minimal inhibition (14.4 +/- 0.3%) of active cGMP transport showed that the extrusion system for cGMP was not shared with cAMP, but a competitive interaction occurred for the ATP-independent association to the inside out vesicles. In contrast, the lowest, but physiological relevant cAMP concentrations (0.1-5 microM) stimulated the active cGMP transport with 30-35%, an observation that suggests cAMP as an allosteric regulator of the cGMP transporter. Several well-known modulators of other energy-requiring membrane transport systems caused a competitive and concentration-dependent inhibition, including verapamil (Ki = 13.0 +/- 2.4 microM), forskolin (Ki = 13.5 +/- 1.4 microM) and probenecid (Ki = 27.0 +/- 1.3 microM). Progesterone, which was the most potent inhibitor (Ki = 2.2 +/- 0.3 microM), interacted with the active cGMP transport in a noncompetitive manner. The highest concentration (100 microM) of IBMX and theophylline reduced the active cGMP uptake with 29.5 +/- 1.9% and 21.6 +/- 2.1%, respectively. None of these substances interfered with the association of cGMP to the vesicles in absence of ATP. The present results show that human erythrocytes possess a cell membrane cGMP transporter which is coupled to an ATPase. Its activity is regulated by cAMP in an apparent allosteric manner and inhibited by substances previously known to interact with other membrane transport systems.
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PMID:Cyclic AMP stimulates the cyclic GMP egression pump in human erythrocytes: effects of probenecid, verapamil, progesterone, theophylline, IBMX, forskolin, and cyclic AMP on cyclic GMP uptake and association to inside-out vesicles. 945 9

Effects of medroxy progesterone acetate (MPA; 5 mg/kg) and MPA + testosterone enanthate (TE) (3 mg + 2 mg/kg) were investigated in vas deferens and on fertility (along with reversibility study) for 60 days through histopathology, morphometric and certain biochemical parameters such as total proteins, sialic acid, ATPase, SDH and testosterone. The study revealed for altered histopathology and contratile pattern of vas deferens resulting in reduced fertility. The study also indicated androgen antagonistic effect. These effects were found to be reversible 4 and 3 months after withdrawal of MPA and MPA + TE injections respectively. Thus, both types generated functional sterility in the rat, but MPA affected histophysiology of vasal tissue.
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PMID:Effect of medroxy progesterone acetate and testosterone enanthate on vas deferens of rats. 975 44


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