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1.
Summary Periodical changes in Ca2+-ATPase and Mg2+-ATPase activity were observed cytochemically in the crayfish gastrolith epithelium during the molting cycle in relation to the calcium transport mechanism. The ATPase activity was demonstrated by a new one-step lead citrate method. The reaction products were mainly restricted to the matrix of type II cell mitochondria. The Ca2+-ATPase activity was intensely observed in two calcium moving stages, the small gastrolith period which indicates the beginning of gastrolith formation, and the aftermolt, when the calcified gastrolith has been dissolved in the stomach and then reabsorbed from the stomach epithelium into the newly formed soft exoskeleton through the blood. Although the intensity of reaction products of Mg2+-ATPase varied in each stage, the enzymatic activity was observed throughout all molting stages. Reaction products were observed in all mitochondria, basement membranes, apical cytoplasmic membranes, and in some lysosomes. In conclusion, periodical changes in the two types of ATPase activity were seen in the mitochondria of gastrolith epithelium during the molting cycle, but Ca2+-ATPase activity seemed to be more prominently synchronized to the calcium movement in the gastrolith epithelium than Mg2+-ATPase activity. These results provide the strong evidence that Ca2+-ATPase may act strongly in the calcium transport system of crayfish molting. 相似文献
2.
In the fungiform papilla of Rana esculenta (Anura Ranidae), the Ca++-ATPase is mainly distributed on the basolateral membrane of the sensory area cells (i.e., neuroepithelial, supporting, and mucous cells). Apical membranes of all cells facing the surface present a slight enzymatic activity. Lateral wall cells have a strong Ca++-ATPase activity on basolateral and apical membranes. Strong Na+, K+-ATPase activity occurs on the apical surface of neuroepithelial cells. Ca++-ATPase activity is absent on the surface of endothelial cells of the capillaries located under the sensory area. These observations lead us to conclude that the sensory area of fungiform papilla is the selective way for calcium influx. Furthermore the absence of ATPase activity on the surface of the endothelial cells indicates that there is no functional barrier to calcium influx into capillary, and that calcium can be removed by vessels from the sensory area. 相似文献
3.
Jeong Hee Hong Qin Li Min Seuk Kim Dong Min Shin Stefan Feske Lutz Birnbaumer Kwong Tai Cheng Indu S. Ambudkar Shmuel Muallem 《Traffic (Copenhagen, Denmark)》2011,12(2):232-245
Polarized Ca2+ signals in secretory epithelial cells are determined by compartmentalized localization of Ca2+ signaling proteins at the apical pole. Recently the ER Ca2+ sensor STIM1 (stromal interaction molecule 1) and the Orai channels were shown to play a critical role in store‐dependent Ca2+ influx. STIM1 also gates the transient receptor potential‐canonical (TRPC) channels. Here, we asked how cell stimulation affects the localization, recruitment and function of the native proteins in polarized cells. Inhibition of Orai1, STIM1, or deletion of TRPC1 reduces Ca2+ influx and frequency of Ca2+ oscillations. Orai1 localization is restricted to the apical pole of the lateral membrane. Surprisingly, cell stimulation does not lead to robust clustering of native Orai1, as is observed with expressed Orai1. Unexpectedly, cell stimulation causes polarized recruitment of native STIM1 to both the apical and lateral regions, thus to regions with and without Orai1. Accordingly, STIM1 and Orai1 show only 40% colocalization. Consequently, STIM1 shows higher colocalization with the basolateral membrane marker E‐cadherin than does Orai1, while Orai1 showed higher colocalization with the tight junction protein ZO1. TRPC1 is expressed in both apical and basolateral regions of the plasma membrane. Co‐IP of STIM1/Orai1/IP3 receptors (IP3Rs)/TRPCs is enhanced by cell stimulation and disrupted by 2‐aminoethoxydiphenyl borate (2APB). The polarized localization and recruitment of these proteins results in preferred Ca2+ entry that is initiated at the apical pole. These findings reveal that in addition to Orai1, STIM1 likely regulates other Ca2+ permeable channels, such as the TRPCs. Both channels contribute to the frequency of [Ca2+] oscillations and thus impact critical cellular functions. 相似文献
4.
The effect of calcium and a soluble cytoplasmic activator on (Ca2+ + Mg2+)-ATPase of density-separated human red cells was investigated. At all calcium concentrations tested, dense (old) lysed cells and their isolated membranes displayed lower activities as compared to the light (young) cells and their membranes. Isolated membranes from all density red cell fractions showed two distinct (Ca2+ + Mg2+)-ATPase activities; one at low calcium and another at moderate calcium concentrations. At high calcium concentration, (Ca2+ + Mg2+)-ATPase activity of isolated membranes was low in all cell fractions. In contrast to the isolated membranes, lysed cells from all density fractions had a maximum (Ca2+ + Mg2+)-ATPase activity only at a low concentration of calcium, while moderate and high calcium concentrations produced low activity. Upon isolation of membranes, a substantial loss of (Ca2+ + Mg2+)-ATPase activity took place from all density cell fractions. Upon membrane isolation, the relative loss of (Ca2+ + Mg2+)-ATPase activity at low Ca2+ concentration was greater in older cells. The extent of stimulation of (Ca2+ + Mg2+)-ATPase by the activator at low calcium concentration was 3–4-fold greater in older cell membranes than in the young ones.These data suggest that the lower (Ca2+ + Mg2+)-ATPase activity in old cells could be accounted for by a selective loss of (Ca2+ + Mg2+)-ATPase activity at low Ca2+ concentration presumably due to reduced affinity of old cell membranes to activator protein. 相似文献
5.
There is growing evidence that intracellular calcium plays a primary role in the pathophysiology of the pancreas in addition to its crucial importance in major physiological functions. Pancreatic acinar cells have a remarkably large amount of Ca2+ stored in both the endoplasmic reticulum (ER) and the acidic stores. The vast majority of the classical ER Ca2+ store is located in the basal part of the acinar cells with extensions protruding into the apical area, however, the acidic stores are exclusively located in the secretory granular area of the cells. Both types of Ca2+ store respond to all three intracellular Ca2+ messengers – inositol trisphosphate (InsP3), cyclic-ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). The two stores interact with each other via calcium-induced calcium release; however, they can be separated using pharmacological tools. The ER relies on sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) that can be blocked by the specific inhibitor thapsigargin. The acidic store requires a low pH that can be modified by blocking vacuolar H+-ATPase. 相似文献
6.
Timothy A. Reinhardt John D. Lippolis 《Biochemical and biophysical research communications》2009,378(1):99-1492
Sixty percent of calcium in milk is transported across the mammary cells apical membrane by the plasma membrane Ca2+-ATPase 2 (PMCA2). The effect of abrupt cessation of milk production on the Ca2+-ATPases and mammary calcium transport is unknown. We found that 24 h after stopping milk production, PMCA2 and secretory pathway Ca2+-ATPases 1 and 2 (SPCA1 and 2) expression decreased 80-95%. PMCA4 and Sarco/Endoplasmic Reticulum Ca2+-ATPase 2 (SERCA2) expression increased with the loss of PMCA2, SPCA1, and SPCA2 but did not increase until 72-96 h of involution. The rapid loss of these Ca2+-ATPases occurs at a time of high mammary tissue calcium. These results suggest that the abrupt loss of Ca2+-ATPases, required by the mammary gland to regulate the large amount of calcium associated with milk production, could lead to accumulation of cell calcium, mitochondria Ca2+ overload, calcium mediated cell death and thus play a part in early signaling of mammary involution. 相似文献
7.
Studies of Ca2+ transport pathways in exocrine gland cells have been useful, chiefly because of the polarized nature of the secretory epithelial cells. In pancreatic acinar cells, for example, Ca2+ reloading of empty intracellular stores can occur solely via Ca2+ entry through the basal part of the plasma membrane. On the other hand, the principal site for intracellular Ca2+ release—with the highest concentration of inositol 1,4,5-trisphosphate (IP3) receptors—is in the apical secretory pole close to the apical plasma membrane. This apical part of the plasma membrane contains the highest density of Ca2+ pumps and is therefore the principal site for Ca2+ extrusion. On the basis of the known properties of Ca2+ entry and exit pathways in exocrine gland cells, the mechanisms controlling Ca2+ exit and entry are discussed in relation to recent direct information about Ca2+ transport into and out of the endoplasmic reticulum (ER) and the mitochondria in these cells. 相似文献
8.
Dr. Satoki Ueno Hikmet Umar Heinz Joachim Bambauer Manfred Ueck 《Cell and tissue research》1984,235(1):3-11
Summary Ca++-ATPase activity was studied ultracytochemically (cf. Ando et al. 1981) in the paraphysis cerebri of the frog. An intense reaction was demonstrated on the plasmalemma of the microvilli at the apical pole of paraphyseal cells; in contrast, the basolateral plasmalemma showed only a slight staining. In addition, mitochondria, gap junctions, cilia, and cytoplasmic elements (e.g., microfilaments) displayed Ca++-ATPase activity. Variation of the Ca++-concentration in the incubation medium from 0.1 mM to 100 mM altered the Ca++-ATPase activity of the cell organelles. The substitution of Ca-by Mg-ions resulted in a conspicuous decrease in the enzyme activity, especially on the apical plasmalemma. Ca++-ATPase activity is claimed to be involved in a number of extra-and intracellular functions. In comparison to the epithelium of the adjacent choroid plexus the paraphyseal epithelial cell is thought to be a principal Ca-ion regulator of the cerebrospinal fluid in frogs.Fellow of the Alexander von Humboldt Foundation 相似文献
9.
Plant cells frequently and rapidly have to respond to environmental changes for survival. Regulation of transport and other energy-requiring processes in the plasmalemma of root cells is therefore one important aspect of the ecological adaptation of plants. Wheat (Triticum aestivum L. cv. Drabant) was grown hydroponically, with or without 50 nM benzyladenine in the medium, and plasma membranes from root cells of 8-day-old plants were prepared by aqueous polymer two-phase partitioning. The influence of Ca2+ and Mg2+ on the plasmalemma ATPase activities was investigated. The presence of benzyladenine during growth increased the ATPase activity, that dependent upon Ca2+ more than that elicited by Mg2+. As a general characteristic, ATP was the preferred substrate, but all nucleotide tri- and diphosphates could be accepted with activities in plasma membranes from control plants of 7-36% (Mg2+) and 40-86% (Ca2+) and in plasma membranes from benzyladenine-treated plants of 12-47% (Mg2+) and 53-102% (Ca2+) as compared with activities obtained with ATP. Nucleotidemonophosphates were not hydrolyzed by the preparations. In preparations from benzyladenine-treated plants one peak of Ca2+-ATPase at pH 5.2–5.6, with a tail from pH 6 and upwards, and one peak of Mg2+-ATPase at pH 6.0–6.5 were observed in the presence of EDTA in the assay media. In preparations from control plants, the addition of EDTA to the assays resulted in a wide optimum between pH 6 and 7 for Mg2+-ATPase and low Ca2+-ATPase activity with no influence of pH in the range 4.5 to 8. Analysis of the pH dependence in the presence of both Ca2+ and Mg2+ indicates that the control plants mainly contain Mg2+-ATPase corresponding to the proton pump. Preparations from benzyladenine-treated wheat roots show, in addition, activation by Ca2+, which, in the slightly alkaline pH range may correspond to a Ca2+-extruding (Ca2++ Mg2+)-ATPase. In the acidic range, the responses are more complicated: the Mg2+-ATPase is inhibited by vanadate, while the Ca2+-ATPase is insensitive, and benzyladenine added during growth influences the interaction between Ca2+ and Mg2+ in a way that parallels the effect of high salt medium. 相似文献
10.
Morphological and functional characterization of the thoracic portion of blowfly salivary glands 总被引:1,自引:0,他引:1
The abdominal portion of the salivary glands in the blowfly has been studied intensively. Here, we examine the thoracic part of the salivary glands, emphasizing structural and functional aspects. The initial segment downstream of the abdominal portion is secretory and resembles the latter in most structural and functional aspects: the apical membrane is enfolded, forms a canalicular system and contains V-H+-ATPase that assembles upon stimulation with the hormone serotonin (5-HT); Na,K-ATPase is localized in the basolateral membrane; septate junctions are not prominent, as deduced from immunofluorescence staining for the marker proteins discs large and fasciclin III. 5-HT elicits, at low concentrations, cytoplasmic [Ca2+] oscillations, and, at saturating concentrations, a tonic [Ca2+] rise. The following, so-called “re-absorptive” segment loops through the coiled secretory portion of the salivary gland. The apical membrane of the re-absorptive cells is not enfolded, and septate junctions are prominent. V-H+-ATPase and Na,K-ATPase reside on the apical and basolateral membranes, respectively. Finally, re-absorptive cells are also sensitive to 5-HT; however, whereas V-ATPase assembly has a 5-HT concentration dependence similar to other segments, the Ca2+ response occurs only at higher 5-HT concentrations, and displays a different kinetic pattern. 相似文献
11.
R. E. Anderson J. W. Kemp W. S. S. Jee D. M. Woodbury 《In vitro cellular & developmental biology. Plant》1984,20(11):837-846
Summary Cultures of osteoblastlike cells obtained from the endosteal surfaces of rabbit long bones formed and mineralized an extracellular
matrix when they were supplied daily with medium containing fresh ascorbate. No matrix formed without this supplementation.
The matrix mineralized whether or not beta-glycerophosphate, a substrate of alkaline phosphatase, was added to the medium.
The ion-transporting ATPase activities of untreated, ascorbate-treated, and ascorbate plus beta-glycerophosphate-treated cells
were measured. Ascorbate-treated and ascorbate plus beta-glycerophosphate-treated cells had similar enzyme activities. The
activities of the Ca2+-ATPase; Ca2+,Mg2+-ATPase; and alkaline phosphatase in treated cells were elevated over the activities in untreated cells. Na+,K+-ATPase activity was lower in treated than in untreated cells. HCO3
−-ATPase activity was not changed by treatment. Alkaline phosphatase activity was 20 times higher in freshly isolated osteoblastlike
cells than in cells grown to confluence in primary culture. In addition, subculturing further reduced the activity of this
osteoblast-marker enzyme. The activities of the ion-transporting ATPases and alkaline phosphatase in second passage cells
were similar to the activities of these enzymes in fresh, noncalcifying tissues. Nevertheless, second passage cells retain
the ability to mineralize an extracellular matrix, and their ion-transporting ATPase and alkaline phosphatase activities are
altered when the cells mineralize a matrix.
This work was supported by Grant NAG-2-108 from the National Aeronautics and Space Administration, Washington, D.C., and Grant
5 PO1 NS15767 from the National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD. 相似文献
12.
《Journal of Plant Interactions》2013,8(1):152-158
Soil salinization in arid zones is a major factor that resulted in the reduction in the yield and quality of many important crops in Northwestern China. In this study, the potential mechanism of flue gas desulfurization gypsum by-product (FGDB) mediated amendment of alkaline soils was investigated in an oil sunflower model by accessing the Ca2+ distribution and Ca2+-ATPase activity in leaf cells. Our results demonstrated an increased calcium concentration, as well as intact chloroplast structure with increasing calcium precipitates in the cell wall, intercellular space, and vacuole of leaf cells in the plants grown in alkaline soils supplied with FGDB or CaSO4. Additionally, a dose-dependent Ca2+-ATPase activity was detected in the plasma membrane and tonoplast of leaf cells from the plants grown in FGDB or CaSO4 supplemented soils. These results implied that the Ca2+-ATPase activity cause cytosolic Ca2+ efflux. The Ca2+ influx is through the Ca2+-channels, and increasing cytosolic Ca2+ concentration might benefit the stability and integrity of cell membrane and cell wall, sequentially alleviated the injury of oil sunflower against alkali stress. 相似文献
13.
Timothy A. Reinhardt John D. LippolisRandy E. Sacco 《Biochemical and biophysical research communications》2014
Plasma membrane Ca2+-ATPase 2 (PMCA2) knockout mice showed that ∼60% of calcium in milk is transported across the mammary cells apical membrane by PMCA2. The remaining milk calcium is thought to arrive via the secretory pathway through the actions of secretory pathway Ca2+-ATPase’s 1 and/or 2 (SPCA1 and 2). However, another secretory pathway calcium transporter was recently described. The question becomes whether this Golgi Ca2+/H+ antiporter (TMEM165) is expressed sufficiently in the Golgi of lactating mammary tissue to be a relevant contributor to secretory pathway mammary calcium transport. TMEM165 shows marked expression on day one of lactation when compared to timepoints prepartum. At peak lactation TMEM165 expression was 25 times greater than that of early pregnancy. Forced cessation of lactation resulted in a rapid ∼50% decline in TMEM165 expression at 24 h of involution and TMEM165 expression declined 95% at 96 h involution. It is clear that the timing, magnitude of TMEM165 expression and its Golgi location supports a role for this Golgi Ca2+/H+ antiporter as a contributor to mammary Golgi calcium transport needs, in addition to the better-characterized roles of SPCA1&2. 相似文献
14.
Secretion in blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT), which activates the InsP3/Ca2+ pathway and the cAMP/protein kinase A (PKA) pathway in the secretory cells. The latter signaling cascade induces the activation
of a vacuolar H+-ATPase on the apical membrane. Here, we have determined the distribution of PKA by using antibodies against the PKA regulatory
subunit-II (PKA-RII) and the PKA catalytic subunit (PKA-C) of Drosophila. PKA is present in high concentrations within the secretory cells. PKA-RII and PKA-C co-distribute in non-stimulated glands,
being enriched in the basal portion of the secretory cells. Exposure to 8-CPT-cAMP or 5-HT induces the translocation of PKA-C
to the apical membrane, whereas the PKA-RII distribution remains unchanged. The recruitment of PKA-C to the apical membrane
corroborates our hypothesis that vacuolar H+-ATPase, which is enriched in this membrane domain, is a target protein for PKA.
This work was supported by grants Wa463/9–5 and GRK837 from the Deutsche Forschungsgemeinschaft. 相似文献
15.
The migration of intestinal epithelial cells from the crypts to the tips of villi is associated with progressive cell differentiation. The changes in Ca2+-ATPase activity and ATP-dependent Ca2+-transport rates in basolateral membranes from rat duodenum were measured during migration along the crypt-villus axis. In addition, vitamin D-dependent calcium-binding protein and calmodulin content were measured in homogenates of six cell populations which were sequentially derived from villus tip to crypt base. Alkaline phosphatase activity was highest at the tip of the villus (fraction I) and decreased more than 20-fold towards the crypt base (fraction VI). (Na+ + K+)-ATPase activity also decreased along the villus-crypt axis but in a less pronounced manner than alkaline phosphatase. ATP-dependent Ca2+-transport in fraction II (8.2 ± 0.3 nmol Ca2+/min per mg protein) and decreased slightly towards the villus tip and base (fraction V). The youngest cells in the crypt had the lowest Ca2+-transport activity (0.9 ± 0.1 nmol Ca2+/min per mg protein). The distribution of high-affinity Ca2+-ATPase activity in basolateral membranes correlated with the distribution of ATP-dependent Ca2+-transport. The activity of Na+/Ca2+ exchange was equal in villus and crypt basolateral membranes. Compared to the ATP-dependent Ca2+-transport system, the Na+/Ca2+ exchanger is of minor importance in villus cells but may play a more significant role in crypt cells. Calcium-binding protein decreased from mid-villus towards the villus base and was undetectable in crypt cells. Calmodulin levels were equal along the villus-crypt axis. It is concluded that vitamin D-dependent calcium absorption takes primarily place in villus cells of rat duodenum. 相似文献
16.
《Cell calcium》2019
The receptor-evoked Ca2+ signal in secretory epithelia mediate many cellular functions essential for cell survival and their most fundamental functions of secretory granules exocytosis and fluid and electrolyte secretion. Ca2+ influx is a key component of the receptor-evoked Ca2+ signal in secretory cell and is mediated by both TRPC and the STIM1-activated Orai1 channels that mediates the Ca2+ release-activated current (CRAC) Icrac. The core components of the receptor-evoked Ca2+ signal are assembled at the ER/PM junctions where exchange of materials between the plasma membrane and internal organelles take place, including transfer of lipids and Ca2+. The Ca2+ signal generated at the confined space of the ER/PM junctions is necessary for activation of the Ca2+-regulated proteins and ion channels that mediate exocytosis with high fidelity and tight control. In this review we discuss the general properties of Ca2+ signaling, PI(4,5)P2 and other lipids at the ER/PM junctions with regard to secretory cells function and disease caused by uncontrolled Ca2+ influx. 相似文献
17.
Membrane preparations from mouse sperm heads and tails were used in a γ32P-ATP hydrolysis assay to investigate Ca2+-dependent ATPase activity. In membranes from sperm heads, but not tails, a Ca2+-dependent ATPase that was further stimulated by calmodulin was detected. The addition of partially purified mouse sperm decapacitation factor (DF) to head membrane preparations significantly stimulated Ca2+-ATPase activity, this effect being further increased in the presence of DF plus calmodulin; in contrast, no response was observed when the same treatment was applied to tail membranes. Sperm preincubated in the presence of trifluoperazine (TFP), a calmodulin antagonist, were significantly more fertile than cells from the same males incubated in the absence of TFP, indicating that inhibition of calmodulin accelerates capacitation. When sperm cells were preincubated briefly, then gently centrifuged to remove DF and resuspended in medium containing 45Ca2+ ± DF, their ability to accumulate 45Ca2+ was significantly lower in the early stages after resuspension in the presence of DF than in its absence. These data correlated with chlortetracycline analysis of the sperm functional state. When cells were centrifuged and resuspended in medium only, there was a noticeable shift from the F pattern (characteristic of uncapacitated cells) to the B pattern (characteristic of capacitated cells), but the reintroduction of DF caused a significant reversion to the F pattern. Finally, using a monoclonal antibody to somatic cell Ca2+-ATPase, we have obtained evidence that the enzyme is particularly localized to the postacrosomal region of the mouse sperm head; specific binding was observed only in permeabilized cells, indicating that the epitope involved in the binding has an intracellular location. Based on these various pieces of evidence, we propose that when present on mouse sperm, DF stimulates calmodulin-sensitive Ca2+-ATPase activity and thus ensures maintenance of a low intracellular Ca2+ concentration. As capacitation proceeds, DF is lost and Ca2+-ATPase activity declines, allowing intracellular Ca2+ to rise and promoting capacitation-related changes. The fact that inhibitors of Ca2+-ATPase and calmodulin appear to accelerate capacitation in several mammalian species, as determined by chlortetracycline analysis, suggests that Ca2+-ATPase activity may play an important role in modulating capacitation in many or even all mammals. © 1996 Wiley-Liss, Inc 相似文献
18.
Previous studies have shown that ferriprotoporphyrin IX (FP) and non-heme iron have a marked inhibitory effect on the Ca2+-Mg2+-ATPase activity of isolated red cell membranes, the biochemical counterpart of the plasma membrane Ca2+ pump (PMCA). High levels of membrane-bound FP and non-heme iron have been found in abnormal red cells such as sickle cells
and malaria-infected red cells, associated with a reduced life span. It was important to establish whether sublytic concentrations
of FP and non-heme iron would also inhibit the PMCA in normal red cells, to assess the possible role of these agents in the
altered Ca2+ homeostasis of abnormal cells. Active Ca2+ extrusion by the plasma membrane Ca2+ pump was measured in intact red cells that had been briefly preloaded with Ca2+ by means of the ionophore A23187. The FP and nonheme iron concentrations used in this study were within the range of those
applied to the isolated red cell membrane preparations. The results showed that FP caused a marginal inhibition (∼20%) of
pump-mediated Ca2+ extrusion and that non-heme iron induced a slight stimulation of the Ca2+ efflux (11–20%), in contrast to the marked inhibitory effects on the Ca2+-Mg2+-ATPase of isolated membranes. Thus, FP and non-heme iron are unlikely to play a significant role in the altered Ca2+ homeostasis of abnormal red cells.
Received: 22 November 1999/Revised: 29 February 2000 相似文献
19.
Ca2+ regulates keratinocyte differentiation by increasing intracellular Ca2+ levels. Ca2+-ATPase in the Ca2+-induced differentiation of human keratinocytes was investigated by measuring Ca2-ATPase mRNA, protein, and activity levels. Human keratinocytes were grown in Keratinocyte Growth Medium containing 0.03, 0.1, or 1.2 mM Ca2+ and assayed on days 2, 5, 7, 14, and 21. Ca2+-ATPase mRNA levels were found to be modestly increased in 5-, 7-, and 14-day cultured cells as compared with 2-day cultured cells, but levels fell below that of the 2-day cultured cells in the 21-day cultured cells. The Ca2+-ATPase mRNA levels were not affected by Ca2+ levels. A 135-kDa protein in human keratinocytes cross reacted with the monoclonal antibody against human erythrocyte Ca2+-ATPase. The level of this protein was decreased by Ca2+ and lost during differentiation, in parallel with the loss of enzymatic activity. Ca2+ influx of postconfluent 1.2 mM Ca2-grown cells was higher than that of cells grown in lower Ca2+ concentrations. Ca2+ efflux from postconfluent cells grown in 0.03 mM Ca2+ was less than that from cells grown in stronger Ca2+ concentrations. These results suggest that the loss of the plasma membrane Ca2+-ATPase with time in culture contributes to the rise in intracelluar Ca2+, thus promoting keratinocyte differentiation. J. Cell. Physiol. 172:146–154, 1997. © 1997 Wiley-Liss, Inc. 相似文献
20.
The effect of hydrocortisone and thyroxine, on the activities of Ca2+-and Mg2+-ATPase was studied in cultured neuronal (clone M1) and glial (clones NN and C6) cell lines. For M1 and NN cells an increase in Ca2+-and Mg2+-ecto-ATPase activity was found when the cells were cultured during 4–6 days in presence of hydrocortisone or together with thyroxine. In the same conditions, a decrease in Ca2+-and Mg2+-ecto-ATPase activity was found for the C6 cells. In C6 cells the effect of hormones was more pronounced for the Mg2+-than for the Ca2+-ecto-ATPase activity. The observed decrease may be related to the tumoral origin of the C6 cells. The activity of (Na+, K+)-ATPase in all three cell lines increased in presence of hydrocortisone or together with thyroxine when the cells were cultured during 4–6 days, in presence of the hormones, whereas the total Mg2+-ATPase activity increased only after 6 days of treatment. Thyroxine alone has very few effect either on Ca2+-and Mg2+-ecto-ATPase, or on (Na+, K+)-and total Mg2+-ATPase activity. These observations are interpreted to indicate that hormones may modulate or induce enzymatic activities involved in active transport phenomena in nervous tissue. 相似文献