1,721,013 research outputs found
Short-term effects of pressure overload on the expression of genes involved in calcium homeostasis
No full textWe investigated whether in the isolated perfused rat heart acute pressure overload may affect the expression of genes involved in calcium homeostasis, namely sarcolemmal L-type Ca2+ channel, Na+/Ca2+ exchanger, sarcoplasmic reticulum Ca2+-ATPase, phospholamban, and ryanodine receptor. Hearts were subjected to 210 min of perfusion under the following conditions: (i) standard working heart perfusion with preload and afterload set at 20 and 100 cm, respectively; (ii) working heart perfusion at high afterload (180 cm); (iii) retrograde infusion of St. Thomas' Hospital cardioplegic solution. In all models gene expression was determined by RT-PCR. Significant decrease in the expression of the sarcoplasmic reticulum Ca2+-ATPase gene was observed in the high afterload group. No significant change in the expression of any other gene was observed in any group. The reported effect was not detected after 60 min of perfusion, and it was blunted in the presence of the protein kinase C inhibitor chelerythrine, while the calcineurin inhibitor cyclosporin A was ineffective. In conclusion, the sarcoplasmic reticulum Ca2+-ATPase gene is downregulated after short-term (210 min) perfusion at high afterload, possibly through a protein kinase C-dependent pathway. This mechanism might play a relevant pathophysiological role in the response to pressure overload and in the development of hypertrophy
Cardioprotective effect of zofenopril in perfused rat heart subjected to ischemia and reperfusion
No full textWe investigated the effect of different ACE inhibitors on tissue injury in isolated rat hearts subjected to 30 minutes of ischemia followed by 120 minutes of reperfusion. Zofenoprilat (1-100 microM), but not enalaprilat or lisinopril, significantly reduced infarct size, as estimated on the basis of triphenyltetrazolium chloride staining. The protection was not reproduced by the angiotensin II receptor antagonist irbesartan, and it was partly abolished by the bradykinin receptor antagonist HOE 140. Zofenoprilat molecule contains a sulfhydryl group, and its administration, as compared with enalaprilat or lisinopril administration, was associated with better preservation of protein thiols at the end of ischemia. We conclude that zofenopril has a specific cardioprotective effect, which might be related either to interference with bradykinin metabolism or to preservation of protein sulfhydryl groups
Modulation of cardiac sarcoplasmic reticulum calcium release by adenosine: a protein kinase C-dependent pathway
No full textWe have already reported that A(3) adenosine receptor stimulation reduces [(3)H]-ryanodine binding and sarcoplasmic reticulum Ca(2+) release in rat heart. In the present work we have investigated the transduction pathway responsible for this effect. Isolated rat hearts were perfused for 20 min in the presence of the following substances: 100 nM N(6)-(iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA), an A(3) adenosine agonist; 10 muM U-73122, a phospholipase C inhibitor; 2 muM chelerythrine, a protein kinase C inhibitor. At the end of perfusion, the hearts were homogenized and [(3)H]-ryanodine binding was assayed. IB-MECA produced a significant decrease in ryanodine binding, which was abolished in the presence of chelerythrine but not in the presence of U-73122. RT-PCR experiments showed that ryanodine receptor gene expression was not affected by IB-MECA. In Western blot experiments, ryanodine receptor phosphorylation on serine 2809 was not modified after perfusion with IB-MECA. We conclude that modulation of SR Ca(2+) release channel by IB-MECA is dependent on protein kinase C activation. However, in this model protein kinase C activation is not due to phospholipase C activation. In addition, changes in ryanodine receptor gene expression or direct phosphorylation of the ryanodine receptor on serine 2809 residue do not appear to occur
Uptake and metabolic effects of 3-iodothyronamine (T1AM) in hepatocytes
No full text3-Iodothyronamine (T1AM) is an endogenous relative of thyroid hormone with profound metabolic effects. In different experimental models, T1AM increased blood glucose, and it is not clear whether this effect is entirely accounted by changes in insulin and/or glucagone secretion. Thus, in the present work, we investigated the uptake of T1AM by hepatocytes, which was compared with the uptake of thyroid hormones, and the effects of T1AM on hepatic glucose and ketone body production. Two different experimental models were used: HepG2 cells and perfused rat liver. Thyronines and thyronamines (T0AMs) were significantly taken up by hepatocytes. In HepG2 cells exposed to 1 μM T1AM, at the steady state, the cellular concentration of T1AM exceeded the medium concentration by six- to eightfold. Similar accumulation occurred with 3,5,3′-triiodothyronine and thyroxine. Liver experiments confirmed significant T1AM uptake. T1AM was partly catabolized and the major catabolites were 3-iodothyroacetic acid (TA1) (in HepG2 cells) and T0AM (in liver). In both preparations, infusion with 1 μM T1AM produced a significant increase in glucose production, if adequate gluconeogenetic substrates were provided. This effect was dampened at higher concentration (10 μM) or in the presence of the amine oxidase inhibitor iproniazid, while TA1 was ineffective, suggesting that T1AM may have a direct gluconeogenetic effect. Ketone body release was significantly increased in liver, while variable results were obtained in HepG2 cells incubated with gluconeogenetic substrates. These findings are consistent with the stimulation of fatty acid catabolism, and a shift of pyruvate toward gluconeogenesis. Notably, these effects are independent from hormonal changes and might have physiological and pathophysiological importance
Modulation of cardiac inotropic state by a novel thyroid hormone analog acting via non genomic mechanism
No full textGhrelin tissue distribution: comparison between gene and protein expression
No full textGhrelin, the natural ligand of the GH secretagogue (GHS) receptor, was originally isolated from the stomach and detected in several tissues, but a systematic study of its tissue distribution has not been performed. In the present investigation, we evaluated ghrelin gene expression (by RT-PCR technique) and ghrelin protein concentration (by enzyme immunoassay technique) in tissues obtained from control rats as well as in rats subjected to 48-h fasting. The ghrelin gene was expressed in stomach, small intestine, brain, cerebellum, pituitary, heart, pancreas, salivary gland, adrenal, ovary and testis, with maximum expression occurring in the stomach, while no significant expression was detected by standard RT-PCR in liver, lung, kidney and skeletal muscle. Ghrelin protein was detected in stomach, small intestine, brain, cerebellum, pituitary, lung, skeletal muscle pancreas, salivary gland, adrenal, ovary and testis, at concentrations ranging from 0.05 to 1.43 ng/mg of homogenate protein (the highest concentration occurred in the lung, followed by the brain). Ghrelin was not detectable in the heart, liver and kidney. Therefore, gene and protein expression were dissociated. Fasting did not produce significant changes in ghrelin gene expression, while the distribution of ghrelin between different tissues was significantly modified: protein concentration increased in the brain, cerebellum, lung and salivary gland, while it decreased in the stomach
Metabolic effects of 3-iodothyronamine in hepatocytes
No full text3-iodothyronamine (T1AM) is an endogenous thyroid hormone derivative which produces profound metabolic effects such as a shift in fuel substrate utilization from carbohydrates to lipid. Thus, in the present work we investigated the effects of T1AM on hepatic glucose metabolism.
To assess metabolite release, human hepatocellular carcinoma cells (HepG2) were exposed for 4 h to different concentrations of exogenous T1AM (0.1, 1 and 10 μM) in glucose production buffer (DME base containing pyruvate and lactate). Cell culture medium was then collected and glucose and ketone body (acetoacetate and β-hydroxybutyrate) levels were evaluated. In addition, isolated rat liver preparations were perfused either with Krebs-Henseleit buffer or glucose production buffer containing 1 μM T1AM. The effluent perfusate was then collected for 60 min at 5 min intervals to measure the release of glucose and ketone bodies (acetoacetate and β-hydroxybutyrate).
In HepG2, only infusion with 1 μM T1AM induced a significant increase in glucose production (9.11±0.37 vs 7.48±0.14 μg/mg of total proteins in cell lysate, P<0.01), and a significant decrease in acetoacetate release (252.4±10.5 vs 286.8±7.2 nmol/ mg of total proteins in cell lysate P<0.05).
Liver perfusion with glucose production buffer in the presence of 1 μM T1AM also showed a significant increase of glucose production (0.555±0.062 vs 0.369±0.043 mg/min per g P<0.05), while infusion with Krebs-Henseleit buffer did not produce any significant change in glucose metabolism.
In conclusions our preliminary data suggested that T1AM stimulated gluconeogenesis and inhibited ketogenesis under conditions of glucose deprivation.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project
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