BACKGROUND: Platelet function is directly influenced by lipoproteins, and platelets from hypercholesterolemic patients display increased reactivity which is related to initiation, progression, and development of thromboembolic complications in atherosclerosis. But the exact mechanism of this effect is unclear. METHODS: In this study, total and activated numbers of platelet glycoprotein (Gp) IIb/IIIa were evaluated in twenty patients (7 men; age, 55.4+/-8.7 years) with hypercholesterolemia (plasma total cholesterol level over 240 mg/dL and normal triglyceride level) and twenty one subjects (8 men; 51.1+/-13.7 years) with normal plasma cholesterol and triglyceride levels. Flow cytometry was used to detect the binding of fluorescein isothiocyanate (FITC)-conjugated anti-CD41 or PAC1 to platelet Gp IIb<1/4>/<1/4>IIIa in whole blood. When whole blood was incubated with PAC1, platelets were also activated with adenosine diphosphate (ADP) or thrombin. RESULTS: PAC1 was more bound to unstimulated platelets from patients with hypercholesterolemia (p<0.005), and binding of PAC1 correlated significantly with plasma total cholesteol (r=0.48, p=0.002) and LDL-cholesterol (r=0.47, p=0.002) levels. Binding of PAC1 to unstimulated platelets increased as binding of anti-CD41 increased (r=0.40, p=0.01). On multivariate linear regression analysis, plasma total cholesterol level and binding of anti-CD41 were independent variables that determined binding of PAC1. After ADP- or thrombin-stimulation, binding of PAC1 to platelets and percentage of antibody positive cells were also greater in patients with hypercholesterolemia (p<0.05). There was a significant positive correlation between mean platelet volume and binding of anti-CD41 to unstimulated platelets (r=0.46, p<0.0050), but the latter was not different between hypercholesterolemia and control groups. CONCLUSION: Unstimulated platelets from patients with hypercholesterolemia had similar total number of Gp IIb/IIIa to those from control subjects, but had more activated Gp IIb/IIIa. After ADP- or thrombin-stimulation, platelet Gp IIb/IIIa was also more activated under hypercholesterolemia.
Adenosine Diphosphate ; Atherosclerosis ; Blood Platelets* ; Cholesterol ; Flow Cytometry ; Fluorescein ; Glycoproteins* ; Humans ; Hypercholesterolemia ; Linear Models ; Lipoproteins ; Male ; Mean Platelet Volume ; Plasma ; Thrombin ; Triglycerides

BACKGROUND AND OBJECTIVES: Regular aerobic exercise plays a role in the prevention of cardiovascular diseases, but the risk of primary cardiac arrest transiently increases during vigorous exercise, particularly in sedentary men. There has been a controversy regarding the effect of exercise on platelet functional behavior, which is related to the pathogenesis of coronary ischemia. We evaluated the cytoplasmic free calcium concentration of platelets in healthy men after treadmill exercise. MATERIALS AND METHOD: Five physically active (group I: age, 24.2+/-2.3 years) and five sedentary men (group II: age, 22.4+/-1.4 years) were included in this study. Platelet calcium was measured with fluorescent dye, quin2 before and after treadmill exercise. RESULTS: Platelet calcium levels were increased from 86.8+/-11.8 nM to 128.8+/-15.0 nM in group I (p<0.05) and from 102.6+/-14.4 nM to 162.4+/-26.5 nM in group II (p<0.05) immediately after exercise. Thereafter, platelet calcium levels were decreased in group I, but continuously increased in group II. At fifteen minutes after exercise, platelet calcium concentrations were significantly higher than baseline values in group II (205.8+/-53.9 nM vs 102.6+/-14.4 nM: p<0.05), but not in group I (115.2+/-15.7 nM vs 86.8+/-11.8 nM). CONCLUSION: Cytoplasmic free calcium concentration in platelets were continuosly increased after treadmill exercise in sedentary men but not in physically active men.
Blood Platelets* ; Calcium* ; Cardiovascular Diseases ; Cytoplasm* ; Exercise ; Heart Arrest ; Humans ; Ischemia ; Male*

BACKGROUND AND OBJECTIVES: Regular aerobic exercise plays a role in the prevention of cardiovascular diseases, but the risk of primary cardiac arrest transiently increases during vigorous exercise, particularly in sedentary men. There has been a controversy regarding the effect of exercise on platelet functional behavior, which is related to the pathogenesis of coronary ischemia. We evaluated the cytoplasmic free calcium concentration of platelets in healthy men after treadmill exercise. MATERIALS AND METHOD: Five physically active (group I: age, 24.2+/-2.3 years) and five sedentary men (group II: age, 22.4+/-1.4 years) were included in this study. Platelet calcium was measured with fluorescent dye, quin2 before and after treadmill exercise. RESULTS: Platelet calcium levels were increased from 86.8+/-11.8 nM to 128.8+/-15.0 nM in group I (p<0.05) and from 102.6+/-14.4 nM to 162.4+/-26.5 nM in group II (p<0.05) immediately after exercise. Thereafter, platelet calcium levels were decreased in group I, but continuously increased in group II. At fifteen minutes after exercise, platelet calcium concentrations were significantly higher than baseline values in group II (205.8+/-53.9 nM vs 102.6+/-14.4 nM: p<0.05), but not in group I (115.2+/-15.7 nM vs 86.8+/-11.8 nM). CONCLUSION: Cytoplasmic free calcium concentration in platelets were continuosly increased after treadmill exercise in sedentary men but not in physically active men.
Blood Platelets* ; Calcium* ; Cardiovascular Diseases ; Cytoplasm* ; Exercise ; Heart Arrest ; Humans ; Ischemia ; Male*

No abstract available.
Female ; Germ Cells* ; Neoplasms, Germ Cell and Embryonal* ; Ovary*

The effect of sodium on p-aminohippurate (PAH) transport kinetics was studied in isolated rat kidney slices in an attempt to define the role of sodium ion in renal organic acid transport. 1. In normally metabolizing renal slices, Na+ increased the Vmax of PAH influx without changing the Michaelis constant (Km). On the other hand, the effIux of preaccumulated PAH was reduced as the Na+ concentration increased. 2. In metabolically impaired renal slices, Na+ had no apparent effect on the influx and efflux of PAH. These results may indicate that Na+ is important for the energy transducing reaction in the PAH transport process.
Aminohippuric Acids/metabolism* ; Animal ; Biological Transport, Active/drug effects ; Culture Media ; Female ; In Vitro ; Kidney/metabolism* ; Kinetics ; Male ; Organ Culture ; Rats ; Sodium/pharmacology* ; p-Aminohippuric Acid/metabolism*

The effects of amphotericin B, an antifungal antibiotic, on erythrocyte volume and cation permeability were investigated by measuring the hematocrit, cell volume, cation content, fragility and osmotic behavior in rat erythrocytes, in vitro. 1. When erythrocytes were incubated in a Ringer solution containing amphotericin B (5-25 microgram/ml) the hematocrit and the cell volume increased, the effect being proportional to the concentration of the drug and the incubation time period. 2. Amphotericin B increased the Na content and decreased the K content of the erythrocyte. In normal Ringer solution (NaCl-Ringer)containing amphotericin B the magnitude of cellular Na gain was greater than that of K loss. Therefore, the total cellular cation content increased. On the other hand, when cells were incubated in the amphotericin B containing Ringer solution in which NaCl was replaced by Na2SO4 (Na2SO4-Ringer) the magnitude of cellular K loss exceeded that of cellular Na gain. Consequently, the total cellular cation content was reduced. 3. Amphotericin B increased cell volume (hematocrit) when erythrocytes were incubated in the Na2SO4-Ringer solution. 4. The fragility of erythrocytes increased when cells were preincubated in the amphotericin B containing normal Ringer solution, whereas it decreased in tile cells preincubated in the amphotericin B containing Na2SO4-Ringer solution. 5. The cell volume was linearly related to the reciprocal of medium osmolality(200 to 900 mOsm/kg H2O) in both NaCl-and Na2SO4-Ringer solutions, and the linearity was not altered by amphotericin B. The antibiotic did not change the slope of the correlation line (V vs. 1/OSM). It, however, increased the intercept of the line with the ordinate in normal Ringer solution and decreased that in the Na2SO4-Ringer solution. These results indicate that amphctericin B alters the cell volume by changing the permeability of Na and K across the membrane.
Amphotericin B/pharmacology* ; Animal ; Erythrocyte Volume/drug effects* ; Erythrocytes/analysis* ; In Vitro ; Osmotic Fragility/drug effects ; Potassium/blood* ; Rats ; Sodium/blood*

Cis-diamminedichloroplatinum II (cisplatin), an effective antitumor agent, induces acute renal failure by unknown mechanisms. To investigate direct toxic effects of cisplatin in the renal proximal tubular transport system, OK cell line was selected as a cell model and Na+/H+ antiport activity was evaluated during a course of cisplatin treatment. The cells grown to confluence were treated with cisplatin for 1 hour, washed, and incubated for up to 48 hours. At appropriate intervals, cells were examined for Na+/H+ antiport activity by measuring the recovery of intracellular pH (pHi) after acid loading. Cisplatin of less than 50 muM induced no significant changes in cell viability in 24 hours, but it decreased the viability markedly after 48 hours. In cells exposed to 50 muM cisplatin for 24 hours, the Na+-dependent pHi recovery (i.e., Na+/H+ antiport) was drastically inhibited with no changes in the Na+-independent recovery. Kinetic analysis of the Na+-dependent pHi recovery indicated that the Vmax was reduced, but the apparent Km was not altered. The cellular Na+ and K+ contents determined immediately before the transport measurement appeared to be similar in the control and cisplatin group, thus, the driving force for Na+-coupled transport was not different. These results indicate that cisplatin exposure impairs the Na+/H+ antiport capacity in OK cells. It is, therefore, possible that in patients treated with a high dose of cisplatin, proximal tubular mechanism for proton secretion (hence HCO3- reabsorption) could be attenuated, leading to a metabolic acidosis (proximal renal tubular acidosis).
Acidosis ; Acute Kidney Injury ; Cell Line ; Cell Survival ; Cisplatin* ; Epithelial Cells* ; Humans ; Hydrogen-Ion Concentration ; Ion Transport* ; Protons

Effects of cadmium (Cd) intoxication on renal endosomal accumulation of organic cations (OC ) were studied in rats using 14C-tetraethylammnium (TEA) as a substrate. Cd intoxication was induced by s.c. injections of 2 mg Cd/kg/day for 2-3 weeks. Renal cortical endosomes were isolated and the endosomal acidification (acridine orange fluorescence change) and TEA uptake (Millipore filtration technique) were assessed. The TEA uptake was an uphill transport mediated by H /OC antiporter driven by the pH gradient established by H -ATPase. In endosomes of Cd-intoxicated rats, the ATP-dependent TEA uptake was markedly attenuated due to inhibition of endosomal acidification as well as H /TEA antiport. In kinetic analysis of H /TEA antiport, Vmax was reduced and Km was increased in the Cd group. Inhibition of H /TEA antiport was also observed in normal endosomes directly exposed to free Cd (but not Cd-metallothionein complex, CdMt) in vitro. These data suggest that during chronic Cd exposure, free Cd ions liberated by lysosomal degradation of CdMt in proximal tubule cells may impair the endosomal accumulation of OC by directly inhibiting the H /OC antiporter activity and indirectly by reducing the intravesicular acidification, the driving force for H /OC exchange.
Animals ; Biological Transport, Active ; Cadmium ; Cations ; Citrus sinensis ; Endosomes* ; Filtration ; Fluorescence ; Ion Transport ; Ions ; Kidney ; Proton-Motive Force ; Rats* ; Tea ; Tetraethylammonium*

The activity of Mg++-dependent, Ca++-activated adenosine triphosphatase (Ca-ATPase) of rat liver mitochondria was studied at varying medium compositions, pH and temperatures. The enzyme system was characteristically sensitive to Ca++ concentration with a KmCa of approximately 0.06 mM. The optimal concentration of Mg was about l mM, above which the enzyme activity was progressively inhibited. The inhibitory effect of high Mg++ concentrations appeared to be due to the alteration of the Mg++/ATP ratio. Variations in the Mg++/ATP ratio affected Vmax but not the KmATP. The pH optimum for enzyme activity increased as the incubation temperature decreased, but the optimal OH-/H+ ratio of the medium was constant at around 0.1, regardless of temperature. The activity of the enzyme was not affected by La# (0.01-1 mM) and Ruthenium red (2.5-10.0 microM). These results indicate that 1) the enzymatic characteristics of the Ca-ATPase system in the rat liver mitochondria is typical of those from other tissue preparations, 2) the enzyme system maintains the most effective catalytic conformation at a fixed level of OH-/H+ ratio of 0.1 when the temperature changes, and 3) the enzyme system may not play a role in the physiological transport of Ca++ in mitochondria.
Animal ; Ca(2+)-Transporting ATPase/metabolism* ; Calcium/pharmacology ; Enzyme Activation/drug effects ; Female ; Hydrogen-Ion Concentration ; Magnesium/pharmacology ; Male ; Mitochondria, Liver/enzymology* ; Rats ; Temperature

Renal Na+, K+-activated adenosinetriphosphatase (Na-K-ATPase) activity and the p-aminohippurate (PAH) transport kinetics were studied in uninephrectomized rats and cold exposed hamsters. In rats, the specific activity of renal Na-K-ATPase increased by approximately 50% in one week after uninephrectomy and remained more or less constant during the next three weeks. The capacity (Jmax) of PAH influx into the renal cortical slice was sharply increased in one week after nephrectomy, but after which it returned to the control level. In cold exposed hamsters, the specific activity of renal Na-K-ATPase did not increase until 48 days of cold exposure at which time it reached approximately 50% above the control level. On the other hand, the Jmax of PAH influx increased by about 80% in 10 days of co1d exposure and somewhat declined thereafter. These results suggest that PAH active transport in the renal slice is not ratelimited by the activity of Na-K-ATPase under physiological conditions.
Aminohippuric Acids/metabolism* ; Animal ; Biological Transport, Active ; Female ; Hamsters ; Hibernation ; Kidney/enzymology* ; Male ; Na(+)-K(+)-Exchanging ATPase/metabolism* ; Nephrectomy ; Rats ; p-Aminohippuric Acid/metabolism*