Chronic renal insufficiency (CRI) is often associated with cardiovascular disease; however, its underlying mechanisms are not completely understood. Therefore, in the present study, myocardial functions and metabolic changes were investigated using an animal model of CRI in subtotally nephrectomized rats. In addition, some other parameters, considered risk factors of cardiovascular diseases, were determined. Subtotal nephrectomy led to an elevation in blood pressure (144±2.8 vs 114±2.5 mm Hg), left ventricular hypertrophy (290±12 vs 200 ±40 mg/100 g b.w.), hypertriglyceridaemia (2.96±0.31 vs 0.77±0.07 mmol/1), and impaired glucose tolerance (AUC 836±12.4 vs 804±10.4 mmol . I-1 . 120 min). Isolated perfused hearts of uraemic rats exhibited diminished basal functions (coronary and aortic flow, stroke volume) by 20 - 30 % compared with the controls. Interestingly, the tolerance of isolated heart to global 20-min no-flow ischaemia was improved in uraemic rats. The most marked differences in heart function recovery during reperfusion concerned aortic flow (90 ± 2.3 vs 66 ± 10 %) and stroke volume (97 ± 2.7 vs 68±5.6% of pre-ischaemic values). Pre-ischaemic myocardial glycogen content was distinctly increased (by 50 %) in uraemic rats compared with the controls.
In contrast to the well-established anti-apoptotic effect of Bcl-2 protein, we have recently demonstrated that Bcl-2 overexpression by vaccinia virus causes apoptosis in BSC-40 cells, while it prevents apoptosis in HeLa G cells. Given the key role of mitochondria in the process of apoptosis, we focused on effects of Bcl-2 expression on mitochondrial energetics of these two cell lines. In this study we present data indicating that BSC-40 cells derive their ATP mainly from oxidative phosphorylation whereas HeLa G cells from glycolysis. More importantly, we show that in both cell lines, Bcl-2 inhibits mitochondrial respiration and causes a decrease of the ATP/ADP ratio. However, it appears that BSC-40 cells cannot sustain this decrease and die, while HeLa G cells survive, being adapted to the low ratio of ATP/ADP maintained by glycolysis. Based on this observation, we propose that the outcome of Bcl-2 expression is determined by the type of cellular ATP synthesis, namely that Bcl-2 causes apoptosis in cells relying on oxidative phosphorylation., M. Vrbacký, J. Krijt, Z. Drahota, Z. Mělková., and Obsahuje bibliografii
In a frog neuromuscular preparation of m. sartorius, glutamate had a reversible dose-dependent inhibitory effect on both spontaneous miniature endplate potentials (MEPP) and nerve stimulation-evoked endplate potentials (EPP). The effect of glutamate on MEPP and EPP is caused by the activation of metabotropic glutamate receptors, as it was eliminated by MCPG, an inhibitor of group I metabotropic glutamate receptors. The depression of evoked EPP, but not MEPP frequency was removed by inhibiting the NO production in the muscle by L-NAME and by ODQ that inhibits the soluble NO-sensitive guanylyl cyclase. The glutamate-induced depression of the frequency of spontaneous MEPP is apparently not caused by the stimulation of the NO cascade. The particular glutamate-stimulated NO cascade affecting the evoked EPP can be down-regulated also by adenosine receptors, as the glutamate and adenosine actions are not additive and application of adenosine partially prevents the further decrease of quantal content by glutamate. On the other hand, there is no obvious interaction between the glutamatemediated inhibition of EPP and inhibitory pathways triggered by carbacholine and ATP. The effect of glutamate on the evoked EPP release might be due to NO-mediated modulation (phosphorylation) of the voltage-dependent Ca2+ channels at the presynaptic release zone that are necessary for evoked quantal release and open during EPP production., S. Adámek ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Purinergic P2X receptors represent a novel structural type of ligand-gated ion channels activated by extracellular ATP. So far, seven P2X receptors subunits have been found in excitable as well as non-excitable tissues. Little is known about their structure, mechanism of channel opening, localization, and role in the central nervous system. The aim of this work is to summarize recent investigations and describe our contribution to elucidating the structure of the ATP binding site and transmembrane domains of the P2X receptor, we also discuss the expression and physiological roles played by the ATP and P2X receptors in the anterior pituitary and hypothalamus., H. Zemková, A. Balík, M. Jindřichová, V. Vávra., and Obsahuje bibliografii a bibliografické odkazy
In the untransformed rice (WT) and transgenic rice with the PEPC and PPDK genes (CK) we determined activities of C4 photosynthetic enzymes, photosynthetic response to irradiance and temperature, the metabolic index of active oxygen, and the yield component factors. The activities of C4 photosynthetic enzymes in WT were very low, while those of corresponding enzymes in CK were highly observable. Moreover, after adenosine triphosphate (ATP) treatment, and under high irradiance and high temperature, the net photosynthetic rate of CK increased by 17 and 12 %, respectively, as compared to that achieved without ATP treatment. The resistance of CK against photo-oxidation was enhanced under these conditions, and CK yield increased by 15 %. ATP treatment enhanced the photosynthetic productivity of CK, thereby proving that ATP is the key factor in enhancing the photosynthetic capacity of transgenic rice with C4 gene. Our new technical approach can be used in breeding rice with high photosynthetic efficiency and high grain yield. and B. J. Zhang ... [et al.].
Proper renal blood flow (RBF) and glomerular filtration rate (GFR)
are critical for maintaining normal blood pressure, kidney
function and water and electrolyte homeostasis. The renal
microvasculature expresses a multitude of receptors mediating
vasodilation and vasoconstriction, which can influence glomerular
blood flow and capillary pressure. Despite this, RBF and GFR
remain quite stable when arterial pressure fluctuates because of
the autoregulatory mechanism. ATP and adenosine participate in
autoregulatory control of RBF and GFR via activation of two
different purinoceptor families (P1 and P2). Purinoceptors are
widely expressed in renal microvasculature and tubules.
Emerging data show altered purinoceptor signaling in
hypertension-associated kidney injury, diabetic nephropathy,
sepsis, ischemia-reperfusion induced acute kidney injury and
polycystic kidney disease. In this brief review, we highlight recent
studies and new insights on purinoceptors regulating renal
microvascular function and renal hemodynamics. We also
address the mechanisms underlying renal microvascular injury
and impaired renal autoregulation, focusing on purinoceptor
signaling and hypertension-induced renal microvascular
dysfunction. Interested readers are directed to several excellent
and comprehensive reviews that recently covered the topics of
renal autoregulation, and nucleotides in kidney function under
physiological and pathophysiological conditions (Inscho 2009,
Navar et al. 2008, Carlstrom et al. 2015, Vallon et al. 2020).
Intact chloroplasts were isolated from dark-senescing primary barley (Hordeum vulgare L.) leaves in order to study selective ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) degradation by the stromal and membrane fractions. RuBPCO specific degradation was estimated and characterised applying sensitive avidin-biotin ELISA method with non-modified or oxidatively modified biotinylated RuBPCO (BR) as substrates. Distinct proteolytic activities were detected. They differed in ATP and divalent metal ion dependence, protease inhibitory profile, and dynamics in the time-course of dark-induced senescence. The results supported involvement of ATP- and metal ion-dependent serine type proteolytic activity against non-modified BR early in induced senescence and appearance of ATP-independent activity at later stage. Active oxygen-modified BR was degraded by ATP-independent serine-type protease probably containing essential SH-groups and requiring divalent metal ions. and L. Simova-Stoilova, K. Demirevska-Kepova, Z. Stoyanova.
The decrease in inorganic phosphate (Pi) content of 10-d-old Phaseolus vulgaris L. plants did not affect rates of photosynthesis (PN) and respiration (RD), leaf growth, and adenylate concentration. Two weeks of phosphate starvation influenced the ATP content and leaf growth more than PN and RD. The ATP concentration in the leaves of 15- and 18-d-old phosphate deficient (-P) plants after a light or dark period was at least half of that in phosphate sufficient (+P, control) plants. Similar differences were found in fresh and dry matter of leaves. However, PN declined to 50 % of control in 18-d-old plants only. Though the RD of -P plants (determined as both CO2 evolution and O2 uptake) did not change, an increased resistance of respiration to KCN and higher inhibition by SHAM (salicylhydroxamic acid) suggested a higher engagement of alternative pathway in respiration and a lower ATP production. The lower demand for ATP connected with inhibition of leaf growth may influence the ATP producing processes and ATP concentration. Thus, the ATP concentration in the leaves depends stronger on Pi content than on PN and RD. and M. Mikulska, J.-L. Bomsel, A. M. Rychter.