Mitochondrial participation in the intracellular Ca2+ network

Calcium can activate mitochondrial metabolism, and the possibility that mitochondrial Ca2+ uptake and extrusion modulate free cytosolic [Ca2+] (Cac) now has renewed interest. We use whole-cell and perforated patch clamp methods together with rapid local perfusion to introduce probes and inhibitors to rat chromaffin cells, to evoke Ca2+ entry, and to monitor Ca2+-activated currents that report near-surface [Ca2+]. We show that rapid recovery from elevations of Cac requires both the mitochondrial Ca2+ uniporter and the mitochondrial energization that drives Ca2+ uptake through it. Applying imaging and single-cell photometric methods, we find that the probe rhod-2 selectively localizes to mitochondria and uses its responses to quantify mitochondrial free [Ca2+] (Cam). The indicated resting Cam of 100-200 nM is similar to the resting Cac reported by the probes indo-1 and Calcium Green, or its dextran conjugate in the cytoplasm. Simultaneous monitoring of Cam and Cac at high temporal resolution shows that, although Cam increases less than Cac, mitochondrial sequestration of Ca2+ is fast and has high capacity. We find that mitochondrial Ca2+ uptake limits the rise and underlies the rapid decay of Cac excursions produced by Ca2+ entry or by mobilization of reticular stores. We also find that subsequent export of Ca2+ from mitochondria, seen as declining Cam, prolongs complete Cac recovery and that suppressing export of Ca2+, by inhibition of the mitochondrial Na+/ Ca2+ exchanger, reversibly hastens final recovery of Cac. We conclude that mitochondria are active participants in cellular Ca2+ signaling, whose unique role is determined by their ability to rapidly accumulate and then release large quantities of Ca2+.

Hyperkalemia associated with cyclosporine (CsA) use in bone marrow transplantation

Two adult leukemia patients underwent allogeneic bone marrow transplantation and received cyclosporine (CsA) as part of their immunosuppressive therapy. Despite adequate kidney function, both patients developed hyperkalemia. Cyclosporine was the only pharmaceutical agent to which this electrolyte abnormality could be attributed. Although the mechanism of the hyperkalemia is unclear, it seems to be related to an aldosterone-resistant state. Cyclosporine-induced hyperkalemia is a relatively common occurrence; however, there is only a single 'case report' addressing this phenomenon in bone marrow transplantation patients. We propose both mechanisms and methods of managing CsA-associated hyperkalemia in allogeneic transplantation patients.

Ca2+ clearance mechanisms in isolated rat adrenal chromaffin cells

1. Intracellular Ca2+ clearance mechanisms were studied in rat adrenal chromaffin cells, by measuring slow tail currents through small-conductance Ca(2+)-activated K+ channels and using indo-1 photometry following depolarization-induced Ca2+ loading. 2. Following several-hundred millisecond depolarizations, [Ca2+]i decayed in three phases. An initial fast decay was followed by a long-lasting, low plateau, then [Ca2+]i returned to the resting level slowly. 3. Replacement of external Na+ moderately slowed [Ca2+]i decay, indicating a contribution of plasma membrane Na(+)-Ca2+ exchange. 4. Raising external pH or application of extracellular Eosin of La3+ prolonged slow tail currents, indicating a contribution of plasma membrane Ca(2+)-ATPase to Ca2+ clearance. 5. Ca(2+)-induced Ca2+ release from caffeine-sensitive stores occurred during depolarization. 6. Inhibition of endoplasmic reticulum Ca(2+)-ATPase had little effect on Ca2+ clearance. 7. Slow tail currents and [Ca2+]i decay following 0.2 - 2 s depolarizations were much prolonged by mitochondrial inhibition with carbonyl cyanide m-chlorophenylhydrazone (CCCP) or Ruthenium Red, which abolished the initial rapid decay and plateau of [Ca2+]i. 8. In conclusion, mitochondrial Ca2+ uptake plays a major role in Ca2+ clearance by rapidly and reversibly sequestering Ca2+ during depolarization-evoked Ca2+ loads.

Dominant role of mitochondria in clearance of large Ca2+ loads from rat adrenal chromaffin cells

Cytosolic Ca2+ (Ca2+c) clearance from adrenal chromaffin cells was studied by whole-cell patch clamp and indo-1 Ca2+ photometry after influx of Ca2+ through voltage-dependent Ca2+ channels. We isolated the rates of Ca2+c clearance by several mechanisms using combinations of the following agents (with their expected targets): Li+ or TEA substituted for Na+ (Na(+)-Ca2+ exchange), 1 mM La3+ applied after the depolarization (Na(+)-Ca2+ exchange and plasma membrane Ca(2+)-ATPase), 1 microM thapsigargin (pumping into reticular stores), and 2 microM carbonyl cyanide m-chlorophenylhydrazone (uptake into mitochondria). Remarkably, whenever [Ca2+]c rose above approximately 500 nM, Ca2+c clearance by mitochondria exceeded clearance by either Na(+)-Ca2+ exchange or the Ca2+ pumps of the plasma and reticular membranes. As [Ca2+]c fell again, Ca2+ reemerged from mitochondria, prolonging the final return to basal levels.

Sphingosine: a mediator of acute renal tubular injury and subsequent cytoresistance

The goal of this study was to determine whether sphingosine and ceramide, second messengers derived from sphingolipid breakdown, alter kidney proximal tubular cell viability and their adaptive responses to further damage. Adult human kidney proximal tubular (HK-2) cells were cultured for 0-20 hr in the presence or absence of sphingosine, sphingosine metabolites (sphingosine 1-phosphate, dimethylsphingosine), or C2, C8, or C16 ceramide. Acute cell injury was assessed by vital dye exclusion and tetrazolium dye transport. Their subsequent impact on superimposed ATP depletion/Ca2+ ionophore-induced damage was also assessed. Sphingosine (> or = 10 microM), sphingosine 1-phosphate, dimethylsphingosine, and selected ceramides (C2 and C8, but not C16) each induced rapid, dose-dependent cytotoxicity. This occurred in the absence of DNA laddering or morphologic changes of apoptosis, suggesting a necrotic form of cell death. Prolonged exposure (20 hr) to subtoxic sphingosine doses (< or = 7.5 microM) induced substantial cytoresistance to superimposed ATP depletion/Ca2+ ionophore-mediated damage. Conversely, neither short-term sphingosine treatment (< or = 8.5 hr) nor 20-hr exposures to any of the above sphingosine/ceramide derivatives/metabolites or various free fatty acids reproduced this effect. Sphingosine-induced cytoresistance was dissociated from the extent of cytosolic Ca2+ loading (indo-1 fluorescence), indicating a direct increase in cell resistance to attack. We conclude that sphingosine can exert dual effects on proximal renal tubular viability: in high concentrations it induces cell necrosis, whereas in low doses it initiates a cytoresistant state. These results could be reproduced in human foreskin fibroblasts, suggesting broad-based relevance to the area of acute cell injury and repair.

The suppression of Ca(2+)- and voltage-dependent outward K+ current during mAChR activation in rat adrenal chromaffin cells

1. The mechanism by which muscarine, ionomycin or caffeine results in suppression of Ca(2+)- and voltage-dependent outward current in rat adrenal chromaffin cells was evaluated using both whole-cell voltage clamp and single channel recording. 2. The whole-cell current activated following the elevation of the cytosolic calcium concentration ([Ca2+]i) by muscarine inactivates with a time course comparable to that of single Ca(2+)- and voltage-dependent potassium (BK) channels. 3. The whole-cell inactivating current is pharmacologically similar to BK current. 4. The voltage dependence of inactivation and rate of recovery from inactivation are qualitatively similar for both whole-cell current and ensemble averages of single BK channels. Furthermore, changes in the rate of whole-cell current inactivation track expected changes in submembrane [Ca2+]. 5. The suppression of outward current can be accounted for solely by inactivation of BK channels and does not depend on the means by which [Ca2+]i is elevated. 6. Muscarinic acetylcholine receptor (mAChR) activation, changes in holding potential (-50 to -20 mV), and step depolarizations of different amplitude and duration were tested for their ability to elevate [Ca2+]i and thereby regulate the availability of BK current for activation. 7. Following muscarine-induced elevation of [Ca2+]i at holding potentials positive to -40 mV, the availability of BK current for activation was typically reduced by more than 50%. 8. Holding potentials in the range of -50 to -20 mV produced only slight alterations in the availability of BK current for activation. 9. Step depolarizations that cause maximal rates of Ca2+ influx (0 to +10 mV) must exceed 200 ms to reduce the availability of BK current by approximately 50%. 10. The results show that the muscarine-induced elevation of [Ca2+]i produces a profound reduction in the availability of BK channels for activation at membrane potentials likely to be physiologically meaningful. Although depolarization- induced Ca2+ influx can inactivate BK current, we propose that short duration depolarizations that occur during normal electrical activity will not significantly alter BK channel availability.

Protein synthesis inhibition induces cytoresistance in cultured human proximal tubular (HK-2) cells

After sublethal injury, proximal tubular cells acquire resistance to further attack. This study evaluated whether this could be a possible consequence of decreased protein synthesis, a potential correlate of cell damage. To this end, cultured human proximal tubular cells (HK-2) were subjected to 0-24 h of protein synthesis inhibition (> 98%), either by adding protein synthesis inhibitors [cycloheximide (CH) or verrucarin A] or by inducing sublethal ATP depletion (antimycin A + 2-deoxyglucose). After 24 h of these treatments, significant resistance to Ca2+ ionophore/ATP depletion-induced attack was noted (assessed by vital dye exclusion, compared with normal cells). That < or = 6 h of protein synthesis inhibition caused no cytoresistance implied the importance of evolving protein depletion rather than nonspecific drug effects or protein synthesis inhibition per se. CH plus ATP depletion did not induce additive benefits, suggesting a common mechanism. Cytoresistance was dissociated from the extent of free Ca2+ loading and ATP depletion but was associated with a decrease in membrane deacylation. CH removal promptly restored protein synthesis and cytoresistance was lost; conversely, ATP recovery did not restore protein synthesis and cytoresistance persisted. The emergence of cytoresistance correlated with the disappearance/dephosphorylation of an unidentified 130-kDa tyrosine-phosphorylated protein/protein complex (denoted pp-130). The functional significance of this change was suggested by the fact that tyrosine phosphatase inhibition with orthovanadate maintained pp-130 expression and prevented the cytoresistant state. We conclude that protein synthesis inhibition in HK-2 cells can induce a cytoresistant state. Suppression in phospholipase activity and altered tyrosine phosphorylation events may have functional significance in this regard.

Severe illness in African children with diarrhoea: implications for case management strategies

To identify clinical disorders associated with severe illness in African children with diarrhoea, we studied a group of under-5-year-olds with diarrhoea who had been brought to a large public hospital in central Cote d'Ivoire. The general condition of children with diarrhoea was assessed and classified according to criteria recommended by WHO, and then used as a nonspecific indicator of severity. Of the 264 children with diarrhoea who were enrolled in the study, 196 had nonsevere illness and 68 severe illness. Children with severe illness were significantly more likely than those with nonsevere illness to be dehydrated (45% versus 11%), moderate-to-severely wasted (47% versus 29%), bacteraemic (26% versus 9%), severely anaemic (haemoglobin level <6 g/dl; 15% versus 6%), have Plasmodium falciparum parasitaemia (27% versus 14%), and have two or more of these five conditions (60% versus 14%). Nontyphoidal Salmonella spp. were present in 68% of the blood isolates but were not associated with seropositivity to human immunodeficiency virus (HIV). The study demonstrates the need for a more comprehensive approach to assessment and management of children with diarrhoea that ensures prompt recognition of bacteraemia, anaemia, wasting and malaria, as well as dehydration. Simple nonspecific observational criteria, such as those recommended by WHO for assessing and classifying general condition, are useful for identifying children with diarrhoea who are at high risk of having life-threatening clinical disorders, and can readily be used by health workers whose clinical training and access to diagnostic laboratory facilities are both limited.

Growth hormone-releasing hexapeptide elevates intracellular calcium in rat somatotropes by two mechanisms

The actions of GH-releasing hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 or GHRP-6) on single rat somatotropes were studied using whole cell patch clamp electrophysiology and indo-1 Ca2+ photometry. GHRP-6 elevated intracellular free Ca2+ ([Ca2+]i) in two phases: a rapid transient phase, followed by a persistent phase. Based on its insensitivity to treatments that block Ca2+ entry [removal of external Ca2+, addition of the dihydropyridine Ca2+ channel blocker nitrendipine (1 microM), and the hyperpolarizing action of zero external Na+ or 100 nM somatostatin], the transient elevation is the result of release of Ca2+ from intracellular stores. The half-maximal concentration for the peak [Ca2+]i rise during Ca2+ release was 49 nM GHRP-6. Prior treatment of cells with caffeine (10 mM) or ryanodine (50 microM) abolished or partially occluded GHRP-6-induced Ca2+ release. Simultaneous measurement of [Ca2+]i and membrane current or potential revealed that the transient release of Ca2+ by GHRP-6 activates a voltage-independent Ca(2+)-activated K+ conductance, which transiently hyperpolarizes the somatotrope. The GHRP-6-induced persistent [Ca2+]i elevation is abolished by removal of external Ca2+ or external Na+ or the addition of 1 microM nitrendipine or 100 nM somatostatin, consistent with Ca2+ entry through voltage-dependent Ca2+ channels. In nondialyzed cells (perforated patch recording), we have identified a long-lasting GHRP-6-induced depolarization which may be responsible for the persistent [Ca2+]i elevation.

Multiple components of voltage-dependent potassium current in normal rat anterior pituitary cells

1. Voltage-dependent K+ currents were studied in normal rat anterior pituitary cells using the patch-clamp technique. To obtain cultures enriched for lactotrophs, density gradient centrifugation was performed on pituitary cells isolated from lactating rats. 2. Depolarizations to about -30 mV from a holding potential of -80 mV activate a rapidly inactivating [time constant (tau) approximately 15-20 ms at -20 mV]K+ current. This transient current activated at low voltages (termed IA) is abolished by 5 mM external 4-aminopyridine (4-AP) but is largely resistant to external tetraethylammonium (TEA) (< or = 30 mM). 3. Recovery from inactivation of IA is fast, with a tau of 100-200 ms at -80 mV. Deactivation is also fast (tau approximately 2.2 ms at -50 mV). The voltage of half-activation of IA is approximately -20 mV. The current is completely inactivated at a holding potential of -40 mV. 4. Voltage-dependent K+ current activated by depolarizations from a holding potential of -40 mV was first detectable at about -20 mV (high voltage-activated) and had a time course that varied among cells. 5. Deactivation of high voltage-activated K+ current was best described by the sum of two exponentials, with tau of about 3.7 and 30 ms at -50 mV. Both components reversed close to the equilibrium potential for K+. 6. The amplitudes of the two tail currents were independent of each other when variable-duration commands were used to activate current. The amplitude of the fast component was largest with 10- to 20-ms commands to +40 mV and was reduced (< or = 50%) with 136-ms commands. The slow component amplitude reached a peak by 40 ms and remained constant for commands < or = 136 ms at +40 mV. 7. The contribution of each component to the total high voltage-activated tail current was variable among cells, with the amount of fast component correlating with the amount of inactivation produced by commands to +40 mV. 8. The two components of tail current activated by depolarizations from the -40 mV holding potential were abolished by external TEA (10 mM). 4-AP (5 mM externally) selectively abolished the fast component of high voltage-activated tail current while only partially reducing the slow component. 9. These results suggest that normal rat anterior pituitary cells possess at least three distinct types of voltage-dependent K+ current: a low voltage-activated, transient current (IA) and two high voltage-activated currents.(ABSTRACT TRUNCATED AT 400 WORDS)

Actions of growth-hormone-releasing hormone on rat pituitary cells: intracellular calcium and ionic currents

Actions of growth-hormone-releasing hormone (GHRH) on single rat anterior pituitary cells were studied using indo-1 fluorescence to monitor changes in intracellular calcium, [Ca2+]i, and perforated-patch recording to measure changes in membrane potential and ionic currents. GHRH elevated [Ca2+]i in non-voltage-clamped cells by a mechanism that was dependent upon extracellular Na+ and Ca2+ and was blocked by the dihydropyridine Ca(2+)-channel blocker, nitrendipine. Resting cells had a fluctuating membrane potential whose a mean value depolarized by 9 mV in response to GHRH. The membrane-permeant cAMP analogue, 8-(4-chlorophenylthio)cAMP, mimicked the action of GHRH on membrane potential. Under voltage clamping, GHRH activated a small inward current (1-5 pA). Two types of response could be distinguished. The type I response had an inward current that was largest at more negative potentials (-90 mV), and the type II response had inward current that was larger at more positive potentials (-40 to -70 mV). Both types of response were reversible and blocked by removal of extracellular Na+. These results suggest that the rise in [Ca2+]i produced by GHRH in non-voltage-clamped cells results from the activation via cAMP of a Na(+)-dependent conductance, which depolarizes the cell and increases the Ca2+ influx through voltage-gated Ca2+ channels.

Characteristics and regulation of a muscarinically activated K current in HSG-PA cells

Whole cell currents were measured in HSG-PA cells (a proposed model for salivary gland duct cells) after muscarinic receptor activation or exposure to known signaling agents. Exposure to carbachol or oxotremorine M produced large and often oscillatory increases in outward current whose reversal potentials indicated a K current. The current was sensitive to extracellular atropine, charybdotoxin, and quinine, but not apamin, and to 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid in the pipette. The response was prolonged or increased by guanosine 5'-O-(3-thiotriphosphate) and mimicked by D-myo-inositol 1,4,5-trisphosphate (IP3) or heparin in the pipette and by extracellular Ca ionophores. Tetraethylammonium indirectly inhibited the response via the muscarinic receptor. Fura 2 in cell suspensions showed that muscarinic agonists increased cytosolic Ca ion concentration ([Ca2+]i) five- to sevenfold, and measurements with indo 1 in individual cells showed that the oscillatory changes in outward current were tightly correlated with parallel changes in [Ca2+]i. The results indicate that muscarinic receptor stimulation of HSG-PA cells activates Ca(2+)-activated K channels through a signaling pathway involving a G protein, IP3 production, and increased [Ca2+]i levels. These findings are similar to those in salivary gland acinar cells.

Kinetic and pharmacological properties of low voltage-activated Ca2+ current in rat clonal (GH3) pituitary cells

1. Low voltage-activated (LVA) Ca2+ current in clonal (GH3) pituitary cells was studied with the use of the whole-cell recording technique. The use of internal fluoride to facilitate the rundown of high voltage-activated (HVA) Ca2+ current allowed the study of LVA current in virtual isolation. 2. In 10 mM [Ca2+]o, detectable LVA current begins to appear at about -50 mV, with half-maximal activation occurring at -33 mV. The time course of activation was best described by a Hodgkin-Huxley expression with n = 3, suggesting that at least three closed states must be traversed before channel opening. 3. Deactivation was found to vary exponentially with membrane potential between -60 and -160 mV, indicating that channel closing is rate-limited by a single, voltage-dependent transition. 4. Onset and removal of inactivation between -40 and -130 mV were best described by the sum of two exponentials. Between -80 and -130 mV, both components of removal of inactivation showed little voltage dependence, with time constants of approximately 200-300 ms and 1-2 s. At membrane potentials above -40 mV, a single component of inactivation onset was detected. This component was voltage independent between -20 and +20 mV (tau = 22 ms). Thus inactivation of LVA current is best described by multiple, voltage-in-dependent processes. 5. Significant inactivation of LVA current occurred at -65 mV without detectable macroscopic current. This suggests that inactivation is not strictly coupled to channel opening. 6. Peak LVA current increased with increasing [Ca2+]o, with saturation approximately 50 mM. The Ca(2+)-dependence of peak LVA current was reasonably well described by a single-site binding isotherm with half-maximal LVA current at approximately 7 mM. 7. LVA current in GH3 cells was largely resistant to blockade by Ni2+. The relative potency of inorganic cations in blocking GH3 LVA current was (concentrations which produced 50% block): La3+ (2.4 microM) greater than Cd2+ (188 microM) greater than Ni2+ (777 microM). 8. Several organic agents, including putative LVA blockers, HVA current blockers and various anesthetic agents, were tested for their ability to block LVA current. The concentrations that produced 50% block are as follows: nifedipine (approximately 50 microM), D600 (51 microM), diltiazem (131 microM), octanol (244 microM), pentobarbital (985 microM), methoxyflurane (1.41 mM), and amiloride (1.55 mM). Phenytoin and ethosuximide produced 36 and 10% block at 100 microM and 2.5 mM, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Halothane inhibits two components of calcium current in clonal (GH3) pituitary cells

The effect of halothane on isolated calcium (Ca2+) current of clonal (GH3) pituitary cells was investigated using standard whole-cell clamp techniques at room temperature. Halothane (0.1-5.0 mM) reversibly reduced both the low-threshold, transient [low-voltage-activated (LVA)] component and the high-threshold [high-voltage-activated (HVA)] component of Ca2+ current. Halothane had little effect on the voltage dependence of activation or inactivation of either component of Ca2+ current. Inhibition of the peak high-threshold Ca2+ current was half-maximal at about 0.8 mM halothane, with maximal inhibition (100%) occurring with 5 mM halothane. When measured at the end of a 190-msec command step, half-maximal reduction of high-threshold current occurred at less than 0.5 mM halothane. The low-threshold transient current was less sensitive to halothane, with half-maximal inhibition of peak transient current activated at -30 mV occurring at approximately 1.3 mM. The effect of halothane on the HVA current was apparently not mediated by changes in intracellular Ca2+ concentration. The ability of halothane to inhibit Ca2+ current was unaffected by either the inclusion of the rapid Ca2+ buffer 1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA) in the recording pipette or exposure of the cell to 10 mM caffeine. To assess the selectivity of the effect of halothane, the actions of halothane on two components of voltage-activated potassium (K+) current observed in the absence of extracellular Ca2+ and on voltage-dependent sodium (Na+) current were also examined. Halothane had no effect on the voltage-dependent, inactivating K+ current of GH3 cells at concentrations up to 1.2 mM. In contrast, the non-inactivating K+ current, though less sensitive to halothane than either Ca2+ current, was reduced by about 40% by 1.2 mM halothane at +20 mV. Peak Na+ current was also blocked by halothane, but 50% block required around 2.6 mM halothane with little effect at 1.6 mM. Reduction of Na+ current was associated with a substantial negative shift in the steady-state inactivation curve. Although the results indicate that a number of voltage-dependent ionic currents are sensitive to halothane, both components of Ca2+ current exhibit a greater sensitivity to halothane than any of three other voltage-dependent currents in GH3 cells. These results show that GH3 cell Ca2+ currents are selectively inhibited by clinically appropriate concentrations of halothane and that the reduction of Ca2+ current can account for the inhibition by halothane of TRH- or KCl-induced prolactin secretion in GH3 cells.

The action of halothane on stimulus-secretion coupling in clonal (GH3) pituitary cells

The effect of halothane on the physiological response to excitatory stimuli was assessed in clonal (GH3) pituitary cells. Halothane, at concentrations used to produce general anesthesia in animals (0.25-0.76 mM), inhibited thyrotropin-releasing hormone (TRH)-induced prolactin (PRL) secretion. The sustained (extracellular calcium-dependent) phase of PRL secretion was 70 +/- 7% inhibited by the highest concentration of halothane tested (0.76 mM); 50% inhibition was produced by approximately 0.4 mM halothane. The early (largely inositol trisphosphate-mediated) phase of secretion was less sensitive to halothane; 0.76 mM halothane produced 18 +/- 2% inhibition of the early phase of secretion. Consistent with these observations, halothane inhibited (IC50 approximately 0.45 mM) the sustained phase of the TRH-induced rise in intracellular calcium ([Ca2+]i) to a greater extent than the initial [Ca2+]i peak. The sustained phase of the [Ca2+]i elevation was inhibited by 75 +/- 7% at the highest concentration of halothane tested (0.76 mM), whereas the peak [Ca2+]i was only inhibited by 14 +/- 5%, consistent with the observation that halothane did not inhibit TRH-stimulated inositide hydrolysis in these cells. Halothane (0.5 mM) did not inhibit phorbol ester- or ionomycin-induced PRL secretion, indicating that halothane has inconsequential effects on the secretory apparatus. Halothane (0.5 mM) also inhibited KCl-induced PRL secretion by 50-80% and the corresponding KCl-induced rise in [Ca2+]i by 68 +/- 6%. These data indicate that halothane inhibits secretagogue-stimulated PRL secretion by reducing the elevation of [Ca2+]i produced by calcium (Ca2+) influx.(ABSTRACT TRUNCATED AT 250 WORDS)

Sulfinyl radical formation from the reaction of cysteine and glutathione thiyl radicals with molecular oxygen

Using Electron Spin Resonance spectroscopy at low temperatures, we find that thiyl radicals resulting from irradiation of frozen aqueous solutions of a variety of thiols, including cysteine, glutathione, and penicillamine react with oxygen to form sulfinyl (RSO.) radicals. The identity of the cysteine sulfinyl radical has been confirmed by the use of molecular oxygen isotopically labeled with 17O. Previous workers have suggested the reaction of thiyl radicals and molecular oxygen resulted in the formation of the potentially damaging thiol peroxyl radical, RSOO.; our work shows no evidence for this species. The sulfinyl radicals are suggested to result from a direct reaction between thiyl radicals and molecular oxygen. This reaction results in the cleavage of the dioxygen bond.

Bone aluminium in haemodialysed patients and in rats injected with aluminium chloride: relationship to impaired bone mineralisation

Iliac bone aluminium was determined by neutron activation analysis in 34 patients with chronic renal failure and in eight control subjects. In 17 patients treated by haemodialysis there was a significant increase in the amount of aluminium (mean +/- SE = 152 +/- 30 ppm bone ash). In eight patients treated by haemodialysis and subsequent renal transplantation, bone aluminium was still significantly increased (92 +/- 4.5 ppm bone ash) but was less than in the haemodialysed patients. In some patients aluminium persisted in bone for many years after successful renal transplantation. There was no relationship between hyperparathyroidism and bone aluminium. Although no statistically significant relationship was found between the mineralisation status of bone and bone aluminium, patients dialysed for the longest periods tended to be those with the highest levels of aluminium, osteomalacia, and dialysis encephalopathy. In 20 rats given daily intraperitoneal injections of aluminium chloride for periods of up to three months, there was accumulation of aluminium in bone (163 +/- 9 ppm ash) to levels comparable to those obtained in the dialysis patients, and after about eight weeks osteomalacia developed. The increased bone aluminium and osteomalacia persisted after injections had been stopped for up to 49 days, although endochondral ossification was restored to normal. As a working hypothesis it is suggested that aluminium retained in the bone of the dialysis patients and the experimental animals interferes with normal mineralisation.

Possible cobalt toxicity in maintenance hemodialysis patients after treatment with cobaltous chloride: a study of blood and tissue cobalt concentrations in normal subjects and patients with terminal and renal failure

The myocardial cobalt concentration in a patient who died 3 months after treatment with cobalt was 25-80 times greater than the concentration in control samples. Blood cobalt concentrations in maintenance hemodialysis patients who had been treated 13-20 months previously with cobaltous chloride were significantly higher than those in maintenance hemodialysis patients who had not received cobalt. Prospective studies of blood cobalt concentrations in maintenance hemodialysis patients and normal subjects after the administration of cobaltous chloride were carried out. It was found that prolonged elevation of blood cobalt concentrations occurred in both normals and maintenance hemodialysis patients, but that the blood cobalt concentrations were much higher in the dialysis patients. The urinary excretion of cobalt following the administration of a single dose of cobaltous chloride was studied in two normal subjects. Cobalt metabolism and toxicity are discussed. In view of the limited therapeutic gains to be expected and because of the lack of information regarding the long term significance of elevated blood cobalt concentrations, it is concluded that cobalt should not be used in the treatment of the anemia of patients with sever renal failure.

Concentration of wear products in hair, blood, and urine after total hip replacement

Raised levels of cobalt and chromium are found in the blood and urine of patients with metallic total hip replacements. When one of the hip components is made of polyethylene much less metal seems to be released from the joint. The long-term effects of the accumulation of chromium in the body need to be studied further.