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Intracellular Free Calcium Concentration (intracellular + free_calcium_concentration)
Selected AbstractsRole of the Na+/Ca2+ exchanger in calcium homeostasis and human sperm motility regulationCYTOSKELETON, Issue 2 2006Zoltán Krasznai Abstract A number of cell functions, such as flagellar beating, swimming velocity, acrosome reaction, etc., are triggered by a Ca2+ influx across the cell membrane. For appropriate physiological functions, the motile human sperm maintains the intracellular free calcium concentration ([Ca2+]i) at a submicromolar level. The objective of this study was to determine the role of the Na+/Ca2+ exchanger (NCX) in the maintenance of [Ca2+]i in human spermatozoa. Spermatozoa maintained in extracellular medium containing ,1 ,M Ca2+ exhibited motility similar to that of the control. In addition to several calcium transport mechanisms described earlier, we provide evidence that the NCX plays a crucial role in the maintenance of [Ca2+]i. Three chemically unrelated inhibitors of the NCX (bepridil, DCB (3,,4, -dichlorobenzamil hydrochloride), and KB-R7943) all blocked human sperm motility in a dose and incubation time dependent manner. The IC50 values for bepridil, DCB, and KB-R7943 were 16.2, 9.8, and 5.3 ,M, respectively. The treatment with the above-mentioned blockers resulted in an elevated [Ca2+]i and a decreased [Na+]i. The store-operated calcium channel (SOCC) inhibitor SKF 96365 also blocked the sperm motility (IC50 = 2.44 ,M). The presence of the NCX antigen in the human spermatozoa was proven by flow cytometry, confocal laser scanning microscopy, and immunoblotting techniques. Calcium homeostasis of human spermatozoa is maintained by several transport proteins among which the SOCC and the NCX may play a major role. Cell Motil. Cytoskeleton 2006. © 2005 Wiley-Liss, Inc. [source] Familial Hypocalciuric Hypercalcemia Caused by an R648stop Mutation in the Calcium-Sensing Receptor Gene ,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2002Mika Yamauchi Abstract In this study, we report an 84-year-old female proband in a Japanese family with familial hypocalciuric hypercalcemia (FHH) caused by an R648stop mutation in the extracellular calcium-sensing receptor (CaR) gene. At the age of 71 years, she presented with hypercalcemia (11.4 mg/dl), hypocalciuria (Cca/Ccr = 0.003), hypermagnesemia (2.9 mg/dl), and a high-serum parathyroid hormone (PTH) level (midregion PTH, 3225 [160,520] pg/ml). At the age of 74 years, a family screening was carried out and revealed a total of 9 hypercalcemic individuals (all intact PTH values <62 pg/dl) among 17 family members tested, thus, being diagnosed as FHH. Two and one-half of three clearly enlarged parathyroid glands were resected, because persistently high PTH levels (intact PTH, 292 pg/ml; midregion PTH, 5225 pg/ml) and the presence of a markedly enlarged parathyroid gland by several imaging modalities (ultrasonography, computed tomography [CT], magnetic resonance imaging [MRI], and subtraction scintigraphy) suggested coexistent primary hyperparathyroidism (pHPT); however, hypercalcemia persisted postoperatively. Histological and immunohistochemical examination revealed that the resected parathyroid glands showed lipohyperplasia as well as normally expressed Ki67, vitamin D receptor (VDR), and the CaR. Sequence analysis disclosed that the proband and all affected family members had a heterozygous nonsense (R648stop) mutation in the CaR gene. This mutation is located in the first intracellular loop; thus, it would be predicted to produce a truncated CaR having only one transmembrane domain (TMD) and lacking its remaining TMDs, intracellular loops, and C-terminal tail. Western analysis of biotinylated HEK293 cells transiently transfected with this mutant receptor showed cell surface expression of the truncated protein at a level comparable with that of the wild-type CaR. The mutant receptor, however, exhibited no increase in intracellular free calcium concentration (Ca2+i) when exposed to high extracellular calcium concentrations (Ca2+o). The proband's clinical course was complicated because of associated renal tubular acidosis (RTA) and nephrotic syndrome. However, it was unclear whether their association affected the development of elevated serum PTH and parathyroid gland enlargement. This report is the first to show that an R648stop CaR mutation yields a truncated receptor that is expressed on the cell surface but is devoid of biological activity, resulting in FHH. [source] Protective effects of steroids from Allium chinense against H2O2 -induced oxidative stress in rat cardiac H9C2 cellsPHYTOTHERAPY RESEARCH, Issue 3 2010Gang Ren Abstract Allium chinense, a traditional herbal medicine, has been used for the treatment of cardiovascular diseases for hundreds of years. In this study, A. chinense steroids (ACSs) including three steroidal glycosides and their parent aglycones were isolated from the bulbs of A. chinense. For the first time, their cardioprotective effects were evaluated in cultured rat cardiac H9C2 cells by pretreatment with ACSs for 24,h before exposure to 0.2,mm H2O2. The results showed the cell viability decreased markedly when H9C2 cells were incubated with 0.2,mm H2O2 alone for 2,h, while the cell lipid peroxidation (estimated by the excessive production of nitric oxide and malondialdehyde) and intracellular free calcium concentration ([Ca2+]i) increased significantly. The addition of 20,,m (below the toxic concentration) of ACSs notably attenuated the cellular injury induced by H2O2. The effects of ACSs in our experiments were similar to those of nimodipine, a clinically applied calcium channel blocker. Preliminary analysis of the structure,activity relationship indicated that ACSs with a spirostane-type skeleton exhibited stronger protection than that with a furostane-type skeleton, and glycosylation of the steroids could substantially lower the protective activities. The above results suggested the protective effects of steroids originated from A. chinense on the oxidative injury of H9C2 cells and ACSs may have potential for preventing cardiac injuries induced by oxidative stress. Copyright © 2009 John Wiley & Sons, Ltd. [source] Immunopotentiation on murine spleen lymphocytes induced by polysaccharide fraction of Panax ginseng via upregulating calcineurin activityAPMIS, Issue 4 2010SONG-DONG ZHANG Zhang S-D, Yin Y-X, Wei Q. Immunopotentiation on murine spleen lymphocytes induced by polysaccharide fraction of Panax ginseng via upregulating calcineurin activity. APMIS 2010; 118: 288,96. Calcineurin (CN), a unique Ca2+/calmodulin (CaM)-dependent serine/threonine protein phosphatase, plays a pivotal role in the activation and proliferation of T lymphocytes. Based on the effective molecular screening model established in our laboratory, we found that a part of polysaccharides from the stem and leaves of Panax ginseng, termed PGP-SL, could activate CN activity. Subsequently, we investigated whether PGP-SL also has immunological competence on murine spleen lymphocytes. In the present study, we demonstrated that PGP-SL could significantly promote in vitro spleen lymphocyte proliferation in the absence of either concanavalin A or LPS in a concentration-dependent manner at concentrations ranging from 100 to 500 ,g/ml (p < 0.001). In addition, the proliferation of cyclosporin A (CsA)-treated spleen lymphocytes was also significantly promoted in the same pattern (p < 0.001); the production of IL-2 was elevated and the effect appeared as early as 24 h after PGP-SL treatment. The results of RT-PCR also indicated that the IL-2 mRNA level was markedly enhanced, particularly at PGP-SL concentrations of 300 and 500 ,g/ml, and Fura-2/AM fluorescence probe analysis showed that PGP-SL could dramatically increase the intracellular free calcium concentration of spleen lymphocytes, i.e. [Ca2+]i was significantly increased by approximately 181 and 107% at 300 and 500 ,g/ml of PGP-SL, respectively. However, this effect could be totally inhibited by verapamil treatment. Taking our results together, we suggest that PGP-SL exhibits immunopotentiation effects on murine spleen lymphocytes by the Ca2+,CN,NFAT,IL-2 signaling pathway. [source] | ||||||||||