The isolated rabbit kidney was perfused with 4 kinds of perfusates which had different ionic compositions, in order to investigate the effects of divalent cations, Mg and Ca, on the renal autoregulation. Four kinds of perfusates are full-balanced perfusate (FBP), perfusate subtracted both CaCl2and MgCI2 from FBP, perfusate subtracted only CaCI, from FBP, and perfusate subtracted only MgCl2 from FBP. The composition of FBP is 6% hydroxyethyl starch in 0.9% NaCl (McGaw Lab. USA) containing Na-acetate 5.0, K2HPO4 5.0, CaCls 1.2, MgCl2 0.5, and glucose 5.O mM/L. Renal Perfusate Flow (RPF) as related to various renal arterial perfusion pressure (RAP) was directly measured with flow-meter attached to the perfusion system. Total renal resistance (Rr) was calculated from RAP & RPF (RT=RAP/RPF). Alterations in renal autoregulation, when different perfusates were perfused, were estimated by pressure-flow curve in every run of perfusion experiments. The results obtained were as follows: 1) Kidney perfused with FBP revealed autoregulation within the range of 100~180 mmHg RAP. Renal Perfusate Flow in the autoregulation zone was 5.0 ml,min/gm. 2) The autoregulation was not appeared in the experiments perfused with the solution subtracted both CaCl2 and MgCI2 from FBP. 3) Kidney perfused with FBP-CaCI2 revealed the autoregulation, which had the autoregulation zone of 110~180 mmHg RAP, and 5. 5 m1/min/gm RPF. However, it was not present in the kidney perfused with FBP-MgCl2. 4) The time course of autoregulation was observed on the pressure-flow curve; autoregulation was continued approximately for 15 minutes, and then deteriorated rapidly. 5) Total renal resistance calculated was proportionately increased as the RAP increased within the regulation zone. Below and above the zone, it was almost inversely related to the RAP. From the above results, it was concluded that Mg is the essential factor in the renal autoregulation and suggested that Mg could have a key role on the neuromuscular transmission, excitability of muscular cell membrane, or the process of intracellular contraction.
Cations, Divalent ; Cell Membrane ; Glucose ; Homeostasis* ; Ions* ; Kidney* ; Magnesium Chloride ; Perfusion ; Starch

Electrical rhythmicity in the gastrointestinal (GI) muscles is generated by pacemaker cells, known as interstitial cells of Cajal (ICC). In the present study, we investigated the effect of external divalent cations on pacemaking activity in cultured ICC from murine small intestine by using whole-cell patch clamp techniques. ICC generated pacemaker currents under a voltage clamp or electrical pacemaker potentials under a current clamp, and showed a mean amplitude of -500+/-50 pA or 30+/-1 mV and the frequency of 18+/-2 cycles/min. Treatments of the cells with external 0 mM Ca2+ stopped pacemaking activity of ICC. In the presence of 2 mM Ca2+, 0 mM external Mg2+ depolarized the resting membrane potential, and there was no change in the frequency of pacemaking activity. However, 10 mM external Mg2+ decreased the frequency of pacemaking activity (6.75+/-1 cycles/min, n=5). We replaced external 2 mM Ca2+ with equimolar Ba2+, Mn2+ and Sr2+, and they all developed inward current in the sequence of Ba2+> Mn2+> Sr2+. Also the frequency of the pacemaking activity was stopped or irregulated. We investigated the effect of 10 mM Ba2+, Mn2+ and Sr2+ on pacemaking activity of ICC in the presence of external 0 mM Mg2+, and found that 10 mM Ba2+ and Mn2+ induced large inward current and stopped the pacemaking activity of ICC (n=5). Interestingly, 10 mM Sr2+ induced small inward current and potentiated the amplitude of pacemaking activity of ICC (n=5). These results indicate that extracellular Ca2+ and Mg2+ are requisite for the pacemaking activity of ICC.
Cations, Divalent* ; Interstitial Cells of Cajal ; Intestine, Small ; Membrane Potentials ; Muscles ; Patch-Clamp Techniques ; Periodicity

BACKGROUND: We have previously shown that the vimentin-positive subset of human breast cancer cell lines, which are more invasive in vitro and in vivo, can activate MMP-2 when cultured on vitrogen gels whereas the poorly invasive, poorly metastatic vimentin-negative subset cannot (J. Cell Physiol. 150: 534, 1992). METHODS: In this study, we compared the interaction of human breast cancer cell lines from each group with respect to the interaction with vitrogen. RESULTS: The cell lines capable of responding to vitrogen for MMP-2 activations showed an enhanced ability to attach to vitrogen-coated culture wells. MCF-7 (non-MMP-2 activating) and MDA-MB-231 (MMP-2 activating) cells were selected for more detailed analysis. MDA-MB-231 cells showed a greater affinity for the 3-dimensional vitrogen than MCF-7 cells. Attachment of both lines to thin coatings of vitrogen was shown to require divalent cations and to be mediated by beta1 integrins. The alpha5 subunit, however, was shown to be involved in fibronectin attachment, but not vitrogen attachment. The GRGDSP peptide dramatically inhibited fibronectin attachment of both cell lines, but did not effect the vitrogen attachment of either. In contrast, the KGDEA recognition sequence for alpha2 integrin inhibited the attachment of MDA-MB-231 cells to vitrogen, but not to fibronectin or laminin. CONCLUSIONS: These results show that the subset of human breast cancer cell lines which respond to the vitrogen gel with MMP-2 activation may interact more easily with the vitrogen, apparently through integrin-mediated recognition. Preliminary analysis reveals that the alpha2beta1 integrin, previously implicated in vitrogen interaction may mediate this response.
Antigens, CD29 ; Breast Neoplasms* ; Breast* ; Cations, Divalent ; Cell Line* ; Fibronectins ; Gels ; Humans* ; Integrin alpha2 ; Laminin ; MCF-7 Cells

BACKGROUND AND OBJECTIVES: Previous studies reported that sodium and potassium play an important role in the pathogenesis of hypertension. Recently attention has been directed towards a possible role of the divalent cations such as calcium, and magnesium. Plasma renin activity is also known to be related to divalent cations heterogeneously. This study investigated the relationships between serum magnesium and ionized calcium and plasma renin activity. MATERIALS AND METHODS: The subjects consisted of 27 essential hypertensive patients and 25 normotensive controls. Criteria for hypertensive group in this study were systolic blood pressure> or =140mmHg or a diastolic blood pressure > or =90mmHg (JNC-VI, 1997). Inclusion criteria were normal urinalysis, no history of systemic illness, no intake of antihypertensive drugs, and no recent intake of any other medication. We took magnesium-loading test for a reliable method of assessing possible magnesium deficiency. RESULTS: There was no significant difference between two groups in serum Magnesium concentration and other electrolytes and plasma renin activity. There was significantly higher rate in hypertensives than in normotensives in magnesium retention(hypertensive vs. normotensive: 63.56+/-12.21% vs. 38.43+/-11.53%, P<0.001). There was significant differences in ionized calcium between high-renin and low-or normo-renin hypertensives(P<0.001). Plasma renin activity was correlated positively with serum ionized calcium in hypertensives(r=.8147; P<0.001). CONCLUSION: These results suggest that plasma renin activity is a factor that can influence on serum ionized calcium in high-renin hypertensives.
Antihypertensive Agents ; Blood Pressure ; Calcium* ; Cations, Divalent ; Electrolytes ; Humans ; Hypertension ; Magnesium Deficiency ; Magnesium* ; Plasma* ; Potassium ; Renin* ; Sodium ; Urinalysis

BACKGROUND AND OBJECTIVES: Previous studies reported that sodium and potassium play an important role in the pathogenesis of hypertension. Recently attention has been directed towards a possible role of the divalent cations such as calcium, and magnesium. Plasma renin activity is also known to be related to divalent cations heterogeneously. This study investigated the relationships between serum magnesium and ionized calcium and plasma renin activity. MATERIALS AND METHODS: The subjects consisted of 27 essential hypertensive patients and 25 normotensive controls. Criteria for hypertensive group in this study were systolic blood pressure> or =140mmHg or a diastolic blood pressure > or =90mmHg (JNC-VI, 1997). Inclusion criteria were normal urinalysis, no history of systemic illness, no intake of antihypertensive drugs, and no recent intake of any other medication. We took magnesium-loading test for a reliable method of assessing possible magnesium deficiency. RESULTS: There was no significant difference between two groups in serum Magnesium concentration and other electrolytes and plasma renin activity. There was significantly higher rate in hypertensives than in normotensives in magnesium retention(hypertensive vs. normotensive: 63.56+/-12.21% vs. 38.43+/-11.53%, P<0.001). There was significant differences in ionized calcium between high-renin and low-or normo-renin hypertensives(P<0.001). Plasma renin activity was correlated positively with serum ionized calcium in hypertensives(r=.8147; P<0.001). CONCLUSION: These results suggest that plasma renin activity is a factor that can influence on serum ionized calcium in high-renin hypertensives.
Antihypertensive Agents ; Blood Pressure ; Calcium* ; Cations, Divalent ; Electrolytes ; Humans ; Hypertension ; Magnesium Deficiency ; Magnesium* ; Plasma* ; Potassium ; Renin* ; Sodium ; Urinalysis

BACKGROUND/OBJECTIVES: Cadmium is a toxic metal that is an occupational and environmental concern especially because of its human carcinogenicity; it induces serious adverse effects in various organs and tissues. Even low levels of exposure to cadmium could be harmful owing to its extremely long half-life in the body. Cadmium intoxication may be prevented by the consumption of dietary components that potentially reduce its accumulation in the body. Dietary chitosan is a polysaccharide derived from animal sources; it has been known for its ability to bind to divalent cations including cadmium, in addition to other beneficial effects including hypocholesterolemic and anticancer effects. Therefore, we aimed to investigate the role of dietary chitosan in reducing cadmium accumulation using an in vivo system. MATERIALS/METHODS: Cadmium was administered orally at 2 mg (three times per week) to three groups of Sprague-Dawley rats: control, low-dose, and high-dose (0, 3, and 5%, respectively) chitosan diet groups for eight weeks. Cadmium accumulation, as well as tissue functional and histological changes, was determined. RESULTS: Compared to the control group, rats fed the chitosan diet showed significantly lower levels of cadmium in blood and tissues including the kidneys, liver, and femur. Biochemical analysis of liver function including the determination of aspartate aminotransferase and total bilirubin levels showed that dietary chitosan reduced hepatic tissue damage caused by cadmium intoxication and prevented the associated bone disorder. CONCLUSIONS: These results suggest that dietary chitosan has the potential to reduce cadmium accumulation in the body as well as protect liver function and bone health against cadmium intoxication.
Animals ; Aspartate Aminotransferases ; Bilirubin ; Cadmium* ; Cations, Divalent ; Chitosan* ; Diet ; Femur ; Half-Life ; Humans ; Kidney ; Liver ; Rats* ; Rats, Sprague-Dawley

TRPM7, a cation channel protein permeable to various metal ions such as Mg2+, is ubiquitously expressed in variety of cells including lymphocytes. The activity of TRPM7 is tightly regulated by intracellular Mg2+, thus named Mg2+-inhibited cation (MIC) current, and its expression is known to be critical for the viability and proliferation of B lymphocytes. In this study, the level of MIC current was compared between immature (WEHI-231) and mature (Bal-17) B lymphocytes. In both cell types, an intracellular dialysis with Mg2+-free solution (140 mM CsCl) induced an outwardly-rectifying MIC current. The peak amplitude of MIC current and the permeability to divalent cation (Mn2+) were several fold higher in Bal-17 than WEHI-231. Also, the level of mRNAs for TRPM7, a molecular correspondence of the MIC channel, was significantly higher in Bal-17 cells. The amplitude of MIC was further increased, and the relation between current and voltage became linear under divalent cation-free conditions, demonstrating typical properties of the TRPM7. The stimulation of B cell receptors (BCR) by ligation with antibodies did not change the amplitude of MIC current. Also, increase of extracellular [Mg2+]c to enhance the Mg2+ influx did not affect the BCR ligation-induced death of WEHI-231 cells. Although the level of TRPM7 was not directly related with the cell death of immature B cells, the remarkable difference of TRPM7 might indicate a fundamental change in the permeability to divalent cations during the development of B cells.
Antibodies ; B-Lymphocytes* ; Cations, Divalent ; Cell Death ; Dialysis ; Ions ; Ligation ; Lymphocytes ; Permeability ; Precursor Cells, B-Lymphoid ; RNA, Messenger

Porphyromonas gingivalis is strongly implicated in the pathogenesis of adult periodontitis, the major cause of tooth loss in adults. Use of an antibacterial agent controlling P. gingivalis as a periodontal therapeutic agent has been rationalized. The present study was performed to observe the antibacterial effect of inorganic polyphosphates (polyP) on P. gingivalis. P. gingivalis 2561 was grown in half-strength brain-heart infusion broth containing hemin and vitamin K with or without polyP. Minimal inhibitory concentration (MIC) of polyP with various chain lengths was determined by measuring the absorbance of the grown cells at 540 nm. MIC of polyP for the bacterium was determined to be 0.05%. The effect of polyP with a chain length of 75 (polyP 75) was further examined. PolyP 75 added to the growing culture of P. gingivalis at its exponential phase was as effective in inhibiting the growth of P. gingivalis as polyP 75 added at the very beginning of the culture. More than 99% of the cells lost their viability determined by viable cell count when polyP 75 was added to the culture of growing P. gingivalis at the concentration of 0.06%, suggesting that polyP 75 has a bactericidal effect on the bacterium. Intracellular nucleotide release from the cells was increased by approx. 20% in the presence of polyP 75 but was not reversed by the addition of divalent cations like Ca++ and Mg++. Under the transmission electron microscope, only a small number of the growing P. gingivalis cells were actually lysed. However, the majority of the cells appeared to be atypical in their shape, demonstrating accumulation of highly electron-dense granules and bodies of condensed nucleic acid-like material in the cytoplasm. In the presence of polyP 75, the protein profile of P. gingivalis was changed as determined by SDS-polyacrylamide gel electrophoresis and immunoblot, and the proteolytic activity of the bacterium demostrated on the zymograms was decreased. The overall results suggest that polyP have a strong bactericidal activity against P. gingivalis in which lysis in relation to chelation may not play the major role but unknown mechanism that possibly affects the viability of the bacterium may be involved. PolyP may be used as an agent for prevention and treatment of periodontitis.
Adult ; Cations, Divalent ; Cell Count ; Chronic Periodontitis ; Cytoplasm ; Electrophoresis ; Hemin ; Humans ; Periodontitis ; Polyphosphates* ; Polyps ; Porphyromonas gingivalis* ; Porphyromonas* ; Tooth Loss ; Vitamin K

Characterization of ceramide-effector(s), which includes protein phosphatase 2A (PP2A) is an important prelude to understanding the molecular basis of sphingolipid-mediated biological effects such as cell growth, differentiation and apoptosis. Recently, the existence of a metal-dependent form of PP2A has been reported (Cai et al., 1995). In this study, we investigated the effects of metal ions and chelators on ceramide-activated PP2A (CAPP). Our study demonstrates that at 0.5 mM concentration, Mg2+ appears to have no significant effect on either basal or ceramide-stimulated phosphatase activities, whereas Ca2+ stimulated the basal phosphatase activity, but was inhibitory towards CAPP. Moreover, the divalent cations Cr2+, Mn2+, Fe2+, Ni2+, Cu2+ and Zn2+ were tested and all were found to be inhibitory towards both CAPP and basal phosphatase activities. By contrast, Cs+ and Li+ had almost no effect on CAPP, although both stimulated basal phosphatase activity. The effects of EDTA and EGTA were tested and it was observed that EDTA decreased CAPP activity in a dose-dependent fashion, but had no effect upon basal phosphatase activity. These results suggest that CAPP is a metal-dependent protein, but, because Ca2+ inhibitied CAPP and EGTA was much less potent than EDTA in inhibiting CAPP, Ca2+ is unlikely to be its metal cofactor.
Cations, Divalent/*pharmacology ; Cell Line ; Edetic Acid/pharmacology ; Egtazic Acid/pharmacology ; Enzyme Activation ; Human ; Lymphocytes/cytology ; Phosphoprotein Phosphatase/drug effects/isolation & purification/*metabolism

Characterization of ceramide-effector(s), which includes protein phosphatase 2A (PP2A) is an important prelude to understanding the molecular basis of sphingolipid-mediated biological effects such as cell growth, differentiation and apoptosis. Recently, the existence of a metal-dependent form of PP2A has been reported (Cai et al., 1995). In this study, we investigated the effects of metal ions and chelators on ceramide-activated PP2A (CAPP). Our study demonstrates that at 0.5 mM concentration, Mg2+ appears to have no significant effect on either basal or ceramide-stimulated phosphatase activities, whereas Ca2+ stimulated the basal phosphatase activity, but was inhibitory towards CAPP. Moreover, the divalent cations Cr2+, Mn2+, Fe2+, Ni2+, Cu2+ and Zn2+ were tested and all were found to be inhibitory towards both CAPP and basal phosphatase activities. By contrast, Cs+ and Li+ had almost no effect on CAPP, although both stimulated basal phosphatase activity. The effects of EDTA and EGTA were tested and it was observed that EDTA decreased CAPP activity in a dose-dependent fashion, but had no effect upon basal phosphatase activity. These results suggest that CAPP is a metal-dependent protein, but, because Ca2+ inhibitied CAPP and EGTA was much less potent than EDTA in inhibiting CAPP, Ca2+ is unlikely to be its metal cofactor.
Cations, Divalent/*pharmacology ; Cell Line ; Edetic Acid/pharmacology ; Egtazic Acid/pharmacology ; Enzyme Activation ; Human ; Lymphocytes/cytology ; Phosphoprotein Phosphatase/drug effects/isolation & purification/*metabolism