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Results for “Potassium Ion Level”

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PubMed1990

Induction of fine structural alteration in cardiac Purkinje cells by ischaemic metabolites depends on oxygen tension.

The effects of major ischaemic metabolites on the fine structure of false tendon Purkinje cells from the dog heart were investigated in vitro under oxygenated and oxygen-deficient conditions. High levels of potassium ion induced potentially reversible alteration consisting of moderate cell swelling, swelling of sarcoplasmic reticulum, and nuclear swelling with moderate aggregation of chromatin irrespective of gas tension. Other metabolites induced alteration only in oxygen-deficient solutions. Ischaemic levels of lactate and inorganic phosphate both caused mitochondrial swelling, which was most severe in the presence of lactate. At acidic pH intramitochondrial dense inclusions, the hallmark of irreversible injury, also developed. Severe aggregation of nuclear chromatin and gross dilatations of the sarcoplasmic reticulum were focal and much less prominent than in contractile myocardium exposed to excess hydrogen ion. These observations indicate that the efflux of ischaemic metabolites from a developing infarct may be arrhythmogenic by impairing the function of the subjacent Purkinje network without damaging its cell structure, since luminal blood flow ensures it is always adequately oxygenated.

Animals↗
PubMed1977

Rat muscle 5'-adenylic acid aminohydrolase. Role of K+ and adenylate energy charge in expression of kinetic and regulatory properties.

The kinetic and regulatory properties of homogeneous AMP deaminase from rat skeletal muscle have ben examined with particular emphasis on (a) the role of potassium ions in the expression of these properties and (b) the role of the adenylate energy charge in the regulation of AMP deaminase activity. Although the enzyme has an absolute requirement for K+, the concentration required for maximum activation is dependent on the concentration of substrate. At saturating levels of AMP (greater than or equal 2.0 mM) maximum activation is observed with 25 mM KCl, whereas at lower substrate concentrations (0.2 mM) approximately 50 mM KCl is needed for maximum activation. Conversely, the response of enzyme activity ot increasing levels of substrate is dependent on the level of potassium ions. At substrating concentrations of K+, the saturation curve for AMP is highly sigmoidal (nh=3.2) whereas at higher KCl concentrations, the apparent cooperativity between AMP sites is almost completely abolished (nh=1.5). The inhibition by a number of phosphorylated metabolites, including ATP, GTP, creatine-P, and P1, is likewise sensitive to the concentration of K+. These results suggest that a significant amount of interaction between K+ sites and both substrate and effector sites is required for the expression of the catalytic and regulatory properties of the enzyme. The specific effects of ATP, creatine-P, and P1 on the parameters of Km and Vmax indicate that each of these profile of AMP deaminase activity generated in response to variations in the adenylate energy charge shows that within the physiological range of energy charge (0.75 to 0.95), the activity increases linearly with decreasesing energy charge and is insensitive to both the total adenylate pool size and the presence of P1 and creatine-P. These data suggest that the most important factor in the regulation of AMP deaminase activity is the state of the energy charge rather than the absolute concentrations of the individual effectors.

AMP Deaminase↗
PubMed1977

Rate-dependent changes in extracellular potassium in the rabbit atrium.

We measured levels of potassium ion in the extracellular space of isolated superfused rabbit atria continuously with double-barreled microelectrodes of which on barrel was a K+ liquid ion-exchanger microelectrode and the other a potential-sensing micropipette. Increases in heart rate resulted in transient increases in extracellular potassium ([K+]0). When the quiescent atrium was stimulated the maximal increase was 0.4 mM at rates of 60/min, 0.7 mM at 90/min, 0.9 mM at 120/min, 1.3 mM at 200/min, and 1.8 mM at 300/min. The increase was not sustained during continued stimulation but declined toward prestimulation levels. When the stimulus was terminated the extracellular potassium activity decreased below bathing solution values by 0.2 mM after 60/min, 0.5 mM after 90/min, 0.7 mM ater 120/min, 0.9 mM after 200/min, and 1.0 mM after 300/min and subsequently returned to a value equal to that of the bathing solution. The magnitude of the decline in extracellular potassium activity during prolonged stimulation was markedly decreased when the bathing solution contained either zero potassium, ouabain, LiCl, or a decreased Po2 such that an elevation in [K+]0 persisted during stimulation. Moreover, the reduction in [K+]0 that followed the cessation of stimulation also was inhibited. These results support a role of the Na-K pump in maintaining extracellular potassium activity during changes in cardiac rate.

Action Potentials↗
PubMed1983

Effects of 4-aminopyridine and 3,4-diaminopyridine on transmitter release at the neuromuscular junction.

The presynaptic effects of 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP) were investigated at the rat diaphragm neuromuscular junction using intracellular recording techniques. 4-AP caused only minor increases in miniature end-plate potential frequency at junctions depolarized with elevated potassium levels. Calcium ions antagonize this excitatory effect. 4-AP (20-200 microM) enhanced evoked transmitter release and the amplitude of the end-plate potentials (EPPs), but this effect was considerably less than predicted from earlier reports. 4-AP (100 microM) enhanced quantal content of the first EPP by only 97% and 3,4-DAP by 95%. 4-AP and 3,4-DAP also enhanced transmitter release during maintained stimulation at 50 Hz. The APs did not exhaust the output capabilities of the nerve terminal. 4-AP and 3,4-DAP blocked facilitation. This is attributed to the observation that 4-AP and 3,4-DAP increases the statistical probability of release to its maximum level (1.0). Increased transmitter release by 4-AP and 3,4-DAP is attributed primarily to their ability to increase the releasable store of transmitter and mobilization activity. It was observed that 4-AP and 3,4-DAP enhances the duration of the EPP. This observation supports the suggestion that 4-AP prolongs the time course of the presynaptic spike. The effects of 4-AP and 3,4-DAP on quantal release are compatible with the hypothesis that these drugs enhance calcium entry indirectly by blocking voltage sensitive potassium channels.

4-Aminopyridine↗
PubMed1987

Clinical trial of gossypol as a male contraceptive drug. Part I. Efficacy study.

The main objective of the research is to study the effectiveness and safety of gossypol as a male contraceptive drug. Using a double-blind, randomized, controlled study design, gossypol was found to be an effective male antifertility drug, with no adverse effects on libido nor appetite. In terms of serum potassium levels, there were no statistical differences between gossypol and placebo groups at the end of the loading phase. However, through the ensuing 12 months of maintenance phase, a statistically significant trend toward reduced serum potassium level was evident.

Appetite↗
PubMed1987

Experiences with gossypol as a male pill.

In 1981 to 1983 we performed a clinical study with gossypol involving 152 participants, and in 1983 to 1985 we conducted another study of 120 participants. The first study was aimed at confirming gossypol's antifertility efficacy and determining the existence of side effects. The objective of the latter study was to find out whether the addition of a potassium salt supplement or a potassium-sparing agent could alleviate the side effect of hypokalemia. In both studies, the participants took a gossypol pill, 20 mg/day for 60 to 75 days for loading, and 50 mg/wk for maintenance. All participants were followed up for a year. The antifertility efficacy was found to be more than 90%, and the chief side effect was lowered serum potassium. In our 1983 to 1985 study, we concluded that since neither potassium supplementation nor triamterene solved the problem, it is very likely that gossypol is a nephrotoxic agent. With 1 year of gossypol treatment, serum testosterone and serum luteinizing hormone showed no change, whereas serum follicle-stimulating hormone showed some elevation after 6 months. The Shanghai researchers found that in their gossypol users, plasma and urinary beta 2-microglobulin levels were elevated to a certain extent. However, 25 subjects in our 1983 to 1985 study showed no appreciable change. Our volunteers had stopped taking gossypol for more than 1 year. In 1986 we started a third study, which was aimed at finding the lowest antifertility dose to minimize possible renal toxicity.

Clinical Trials as Topic↗
PubMed1997

Gossypol-induced hypokalemia and role of exogenous potassium salt supplementation when used as an antispermatogenic agent in male langur monkey.

In our earlier study, we have observed that hypokalemia in langur monkeys, following gossypol acetic acid (GAA) treatment (5 mg dose level) when used as an antispermatogenic agent, and potassium salt supplementation partially maintained body potassium level of the animals. The aims of the present investigation was to confirm further occurrence of hypokalemia in the monkey (comparatively at two higher dose levels) and the role of potassium salt in preventing occurrence of gossypol-induced hypokalemia. Highly purified gossypol acetic acid alone at two dose levels (7.5 and 10 mg/animal/day; oral) and in combination with potassium chloride (0.50 and 0.75 mg/animal/ day; oral) was given for 180 days. Treatment with gossypol alone as well as with the supplementation of potassium salt resulted in severe oligospermia and azoospermia. Animals receiving gossypol alone showed significant potassium deficiency with signs of fatigue at both dose levels. Enhanced potassium loss through urine was found in potassium-deficient animals, whereas animals receiving gossypol acetic acid plus potassium salt showed normal serum potassium with a less significant increase in urine potassium level during treatment phases. Other parameters of the body remained within normal range except gradual and significant elevation in serum transaminases activity. The animals gradually returned to normalcy following 150 and 180 days of termination of the treatment.

Animals↗
PubMed1992

Serum and endometrial sodium and potassium levels with inert and copper-containing IUCDs and relation to serum steroid levels.

Serum and endometrial sodium (Na) and potassium (K) levels and serum estradiol, progesterone, testosterone and cortisol were measured in the mid-follicular and mid-luteal phases of the menstrual cycle in 20 Lippes loop and 20 CuT-200 IUCD users and 20 matched controls. Na and K were measured by atomic absorption spectrophotometry, while serum steroids were measured by RIA. Regarding steroids, the only significant difference between the three groups was a significantly lower mean mid-luteal serum estradiol in CuT-200 IUCD users compared to Lippes loop users (p less than 0.05). Regarding sodium in the control group, there was significantly lower mean mid-luteal serum and endometrial Na (p less than 0.01) that was not found in both groups of IUCD users. In the mid-follicular phase, there was significantly higher mean serum Na in both Lippes loop and CuT-200 groups compared to controls (p less than 0.05). Mean endometrial Na showed no significant difference between the three groups in both phases of the menstrual cycle. Regarding potassium in the control group, there was significantly lower mean levels in the mid-luteal-phase of the cycle (p less than 0.01) that was not seen with both groups of IUCD users. Serum K showed no significant difference in the three groups in both phases of the menstrual cycle. Endometrial K showed a significantly higher mean level in both Lippes loop and CuT-200 IUCD users compared to controls in the mid-luteal (p less than 0.01), but not in the mid-follicular phases of the cycle.

Analysis of Variance↗
PubMed1983

Prevalence of secondary hypertension in a population sample of Swedish women.

In a comprehensive population study of 1462 women aged 38--60 in Göteborg, Sweden, the prevalence of secondary hypertension was estimated to be 0.8% of the total population sample and 4.6% of those who were hypertensive (defined as systolic blood pressure greater than or equal to 160 mmHg or diastolic blood pressure greater than or equal to 95 mmHg or both or antihypertensive treatment irrespective of blood pressure levels). These figures were based on thorough clinical and laboratory investigations and a follow-up period of 12 years. Women with arterial hypertension reported a history of toxaemia of pregnancy and a family history of hypertension more often than non-hypertensive women. In comparison with non-hypertensive women, in both untreated and treated hypertensive women, serum uric acid, urinary methoxycatecholamine excretion, body weight and the prevalence of albuminuria were increased and serum potassium decreased (statistically significant differences).

Adrenal Cortex Hormones↗
PubMed1996

Hypokalemia in a pediatric intensive care unit.

OBJECTIVE: To examine the frequency, severity, risk factors and mortality of hypokalemia, and efficacy of therapy used for its correction. DESIGN: Descriptive, retrospective analysis. SAMPLE: 290 patient records admitted consecutively to a Pediatric Intensive Care Unit (PICU) over a period of one year. RESULTS: Forty three (14.8%) patients had 54 episodes of hypokalemia. Predisposing factors included the nature of primary disease (renal disease 19%, septicemia 19%, acute diarrhea 14%, heart disease with congestive failure, and meningoencephalitis 12% each), malnutrition (weight for age less than 80% in 72%) and therapy with drugs (diuretics, corticosteroids and antiasthma drugs). For correction of hpokalemia all the patients received 4-6 mEq potassium per 100 ml of intravenous fluids (slow correction). Seven patients (9 episodes), with ECG changes of hpokalemia, also received infusion of 0.3 mEq potassium/kg/hour till ECG became normal (rapid correction). Normal potassium level was achieved in all nine episodes where rapid correction was given, and in 40 of 45 episodes which received slow correction. The overall mortality among patients with hypokalemia (25.6%, 11/43) was significantly higher than that among the remaining PICU patients (10.9%, 27/247; odd's ratio 2.34; 95% confidence interval 1.3-4.2) (p < 0.05). All the patients receiving rapid correction survived. CONCLUSIONS: Hypokalemia is a common problem among PICU patients. Early detection through regular monitoring and rapid correction may help in improving the outcome.

Age Distribution↗
PubMed1990

Effects of gossypol on the motility of mammalian sperm.

The effects of the male contraceptive gossypol on the motility of mammalian spermatozoa are reviewed. The role of sperm motility in the processes of fertilization and the effect of the drug on these processes determine its effectiveness as a contraceptive. The promising male contraceptive potential of gossypol is discussed in the context of the serious adverse effects of the agent.

Animals↗
PubMed1976

Effect of oral contraceptives on rhythmic urinary metal excretion.

Thirteen women, six of whom were using oral contraceptive agents, between the ages of 23 and 34 years, free from illness, and without a previous clinical history of menstrual abnormality, were studied with chronobiological methods for circadian (about 24 hour) patterns of metal and creatinine excretinine excretion. Circadian rhythms were detected for the excretion of lithium, potassium, iron, sodium, copper, and creatinine. Statistically significant by lower 24 hour excretion (mesors) of lithium, potassium, and iron was detected for the subjects using oral contraceptive agents. Although all women adhered to nearly identical activity-rest (synchronization) schedules, the peak times (acrophases) of the metal excretory rhythms for oral contraceptive users were phase delayed by about two hours.

Adult↗
PubMed1989

Slow inactivation and reactivation of the K+ channel in squid axons. A tail current analysis.

Potassium current inactivation and reactivation in squid axons were measured from tail current amplitudes after voltage clamp prepulses to the potassium equilibrium potential, EK, in seawater containing elevated levels of potassium ion concentration, Ko. Little or no inactivation resulted with prepulses lasting less than 100 ms. Longer pulses caused the current to inactivate in two phases, one between 0.1 and 1 s, and a second phase between 5 and 100 s. Inactivation was incomplete. The time constant of the tail current after a prepulse to EK was independent of pulse duration (0.1-120 s). Inactivation was independent of Ko (10 less than or equal to Ko less than or equal to 300 mM), and it was independent of membrane potential, V, for -40 less than or equal to V less than or equal to 0 mV. Reactivation was measured with a three-pulse protocol. The reactivation time course was sigmoidal with a delay of approximately 100 ms before significant reactivation occurred. These results were described by a model consisting of three inactivated states arranged in a linear sequence. The rate constants of the model are of the form (A + B exp (CV), or 1/(A + B exp (CV], which are required to describe the non-inactivating conductance component.

Animals↗
PubMed2002

Properties of the chaperonin complex from the halophilic archaeon Haloferax volcanii.

The halophilic archaeon Haloferax volcanii has three genes encoding type II chaperonins, named cct1, cct2 and cct3. We show here that the three CCT proteins are all expressed but not to the same level. All three proteins are further induced on heat shock. The CCT proteins were purified by ammonium sulphate precipitation, sucrose gradient centrifugation and hydrophobic interaction chromatography. This procedure yields a high molecular mass complex (or complexes). The complex has ATPase activity, which is magnesium dependent, low salt-sensitive and stable to at least 75 degrees C. Activity requires high levels of potassium ions and was reduced in the presence of an increasing concentration of sodium ions.

Adenosine Triphosphatases↗