X-linked pyruvate dehydrogenase E1 alpha subunit deficiency in heterozygous females: variable manifestation of the same mutation

Three female patients are described with pyruvate dehydrogenase (PDH) deficiency as a result of mutation in the X-linked gene for the E1 alpha subunit of the complex. Two of these patients illustrate typical presentations of PDH E1 alpha deficiency, with severe neurological dysfunction, degenerative changes and developmental anomalies in the brain, together with variable lactic acidosis. The third patient extends the known spectrum of the condition to include mild to moderate mental retardation and seizures in an adult. All three patients have the same mutation in the PDH E1 alpha gene. This mutation, a C-to-T substitution in a CpG dinucleotide in amino acid codon 302 (designated R302C), results in the replacement of arginine by cysteine at this position. The mildly affected adult was the mother of one of the other patient, making this the first described instance of mother-to-daughter transmission of a mutation causing PDH E1 alpha deficiency. The genetic basis of the variable expression of X-linked PDH E1 alpha deficiency in heterozygous females is discussed.

Mutations and polymorphisms in the pyruvate dehydrogenase E1 alpha gene

We present an update on mutations and polymorphisms in the human X chromosome located pyruvate dehydrogenase E1 alpha gene. A total of 20 different mutations are tabulated. The mutations include deletions, insertions, and point mutations. Certain sequences seem particularly prone to mutation. Most of the mutations are found in exons 10 and 11. Furthermore, four of the mutations are seen in unrelated patients. Little is known about how the mutations affect the structure or function of the pyruvate dehydrogenase complex.

[Chronic subgaleal abscess as a cause of eyelid swelling]

A 36 year-old female patient presented with a massive swelling of the eyelid, cheek, and neck. We could not explore any cause for those swellings. Finally, magnetic resonance imaging of the head showed a hugh subgaleal abscess. It was caused by minor scalp trauma.

[Automatic perimetry of the central visual field in diseases of the macula]

We developed a program for testing the central 12 degrees of the visual field with a spatial resolution of 1.6 degrees that was easy to operate. The program was designed for the Octopus computer-perimeter and created by means of the SARGON-utility. Our way of examining differed slightly from the standard Octopus procedure. We tested 16 normal eyes and 13 eyes of patients with various diseases of the central retina. Our normal values of differential threshold sensitivities were about 1.8 dB below the normal values of the Octopus system. Sensitivity and specificity of the program were nearly identical irrespective of using our normal values or the Octopus normal values for the calculation of the above mentioned parameters. Sensitivity was 84.6%, specificity 87.5%. The ability of the program to correctly localize retinal defects was shown. The program was designed for follow-up of patients having undergone paramacular lasercoagulation.

[Sudden blindness in an AIDS patient. Simultaneous infection with cytomegalovirus and herpes simplex viruses and development of malignant non-Hodgkin lymphoma]

A 50 year old patient with non-diagnosed HIV-infection at onset of his illness developed impairment of vision and temporary double vision combined with severe hemianopsia. With normal fundus and suspicious Herpes simplex iritis therapy with Acyclovir was started. Primarily the patient showed a good response to the therapy and loss of vision could be prevented. After 4 weeks CMV-retinitis developed. In spite of Gancyclovir therapy manifestation of total loss of vision after 6 weeks. Autopsy demonstrated signs of simultaneous a CMV-infection of the retina and a herpes simplex-infection of the optic nerve combined with a Non-Hodgkin-Lymphoma of the optic tract.

Polymorphisms in the human X-linked pyruvate dehydrogenase E1 alpha gene

Pyruvate dehydrogenase E1 alpha deficiency is an X-chromosome-linked disorder, often with fatal consequences. We have searched for genetically useful polymorphisms in or near this gene. No restriction fragment length polymorphisms were detected using a battery of 36 different restriction enzymes and probing with a full-length cDNA fragment, or two single-copy genomic fragments located within intron 8, and 15 kb 3' of the coding region, respectively. The chemical cleavage method was then applied to the detection of base changes in or near the gene. One polymorphism was found in exon 8 of the coding region. However, no base changes were detected in intron 3 or in the part of intron 8 covered by fragment gB2. Three blocks of microsatellite DNA containing variable numbers of CA-repeats were isolated from the 5' end of the gene and characterized. Length polymorphisms in these microsatellite DNAs were analysed using the polymerase chain reaction. Although the three loci are tightly linked, the polymorphisms appear not to be in disequilibrium, making them useful markers in linkage studies of the pyruvate dehydrogenase E1 alpha gene. Of 31 females analysed 12(39%) were heterozygous for at least one length polymorphism of the three (CA)n alleles.

Competition ELISA using a human monoclonal antibody for detection of antibodies against human immunodeficiency virus type 1

A novel competition ELISA for detection of antibodies against HIV-1 was developed. The assay is based on competition at the single epitope level and utilises a human monoclonal antibody and an E. coli-produced fragment of the transmembrane glycoprotein gp41. The sensitivity of the assay was 100% in tests on 247 serum samples obtained from 219 individuals previously shown to be HIV-1 antibody positive by both conventional indirect ELISA and the immunoblotting test. The patients represented various clinical and immunological stages of HIV-1 infection. Likewise, the specificity of the assay was 100% in tests on 105 serum samples from normal individuals previously tested negative by indirect ELISA. Further, among 105 serum samples selected due to consistent false positive reactions in the indirect ELISA only 2 samples (1.9%) demonstrated false positive reactions in the competition ELISA, i.e. 98.1% specificity. Finally, only 2 of 57 (3.5%) serum samples from HIV-2 infected individuals showed positive reactions in the assay, while 54 (94.7%) had absorbance values similar to the negative controls. These results demonstrate that human monoclonal antibodies may form the basis for highly sensitive and specific assays for detection of antibodies to HIV-1.

Characterization of the mutations in three patients with pyruvate dehydrogenase E1 alpha deficiency

The human pyruvate dehydrogenase complex catalyses the oxidative decarboxylation of pyruvate to acetyl-CoA. Defects in several of the seven subunits have been reported, but the majority of mutations affect the E1 component and especially the E1 alpha subunit. However, the clinical presentation of patients with pyruvate dehydrogenase E1 alpha deficiency is extremely variable. Dependency of the brain on pyruvate dehydrogenase activity and localization of the gene for the somatic form of the pyruvate dehydrogenase E1 alpha subunit to the X chromosome provide the basis for a better understanding of the variation in the clinical manifestations. Further understanding of the function and interaction of subunits and the pathophysiology of pyruvate dehydrogenase deficiency necessitates the characterization of mutations in the pyruvate dehydrogenase complex. We report the analysis of three patients with pyruvate dehydrogenase E1 alpha deficiency. One female has a three base pair deletion which affects dephosphorylation of the subunit. Of two males analysed, one has a two base pair deletion causing a shift in the reading frame. The other has a base change, resulting in an Arg to His substitution. All three mutations are located near the carboxyl terminus of the subunit.

Haemorheological changes in patients with retinal vein occlusion after isovolaemic haemodilution

In 83 patients with central retinal vein occlusion and branch vein occlusion we measured the haematocrit (HCT), plasma viscosity (PV), red cell aggregation (RCA), red cell filterability (RCF) and apparent whole blood viscosity (WBV). A control group (n = 41) was matched for sex, age, and cardiovascular risk factors. Measurements were performed before and after treatment with isovolaemic haemodilution (IHD). We found no significant differences between patients with retinal vein occlusion (RVO) and control subjects in haematocrit, plasma viscosity, red cell aggregation, and red cell filterability and no increased whole blood viscosity in the patient group. Patients with ischaemic retinal vein occlusion and non-ischaemic retinal vein occlusion did not show different haemorheological parameters either. After treatment with haemodilution, only the haematocrit and whole blood viscosity were significantly decreased, and there were no changes in plasma viscosity, red cell aggregation or red cell filterability.

Analysis of a highly immunodominant epitope in the human immunodeficiency virus type 1 transmembrane glycoprotein, gp41, defined by a human monoclonal antibody

A human monoclonal antibody, 41-7 [immunoglobulin G1(kappa)], directed against the transmembrane glycoprotein gp41 of the human immunodeficiency virus type 1 (HIV-1) has been produced by direct fusion of lymph node cells from an HIV-1-infected individual with a human B-lymphoblastoid cell line. The minimal essential epitope for 41-7 was mapped to a conserved seven-amino acid sequence, N-CSGKLIC-C, located within the N-terminal part of gp41. Antibodies blocking the binding of 41-7 could be detected in the serum of all HIV-1-infected individuals tested, irrespective of the stage of the infection. The epitope is located externally to the plasma membrane, and it is accessible to antibody in the native conformation of the glycoprotein. Despite this, no neutralizing activity of 41-7 could be demonstrated in vitro. These data indicate, directly and indirectly, that this immunodominant epitope on gp41, although exposed on the viral surface, elicits antibodies lacking antiviral activity and, hence, should be avoided in future vaccine candidates.

Pyruvate dehydrogenase deficiency caused by deletion of a 7-bp repeat sequence in the E1 alpha gene

A 7-bp deletion in the X-chromosomal pyruvate dehydrogenase (PDH) E1 alpha gene was characterized in a female patient with the "cerebral" form of PDH deficiency. The mutation was localized using the chemical cleavage method and further characterized by application of the polymerase chain reaction and DNA sequencing. This 7-bp sequence is found in the normal gene as a direct tandem repeat. The deletion causes a change in the reading frame. Results have shown that the level of normal sized PDH E1 alpha in the fibroblast sample was approximately 30% of that of normal controls. This is consistent with normal transcription from the X chromosome carrying the nonmutated form of the E1 alpha subunit, as this chromosome is active in approximately 30% of this patient's cells. The severity of PDH E1 alpha deficiency in affected females is to a large extent dependent on the X-chromosome inactivation pattern in the brain. The clinical picture might therefore vary significantly between patients with the same mutation. We show that the 7-bp deletion must be a de novo mutation, because it is not present in the parent's X chromosomes. Furthermore, the deletion was not detected in chorionic villus samples in two subsequent pregnancies.

Inhibition of human immunodeficiency virus (HIV) infection in vitro by anticarbohydrate monoclonal antibodies: peripheral glycosylation of HIV envelope glycoprotein gp120 may be a target for virus neutralization

Carbohydrate structures are often involved in the initial adhesion of pathogens to target cells. In the present study, a panel of anticarbohydrate monoclonal antibodies (MAbs) was tested for their ability to inhibit in vitro human immunodeficiency virus infectivity. MAbs against three different N- and O-linked carbohydrate epitopes (LeY, A1, and sialyl-Tn) were able to block infection by cell-free virus as well as inhibit syncytium formation. Inhibition of virus infectivity was independent of virus strain (HTLVIIIB or patient isolate SSI-002), the cell line used for virus propagation (H9 or MT4), and the cell type used as the infection target (MT4, PMC, or selected T4 lymphocytes). Inhibition was observed when viruses were preincubated with MAbs but not when cells were preincubated with MAbs before inoculation, and the MAbs were shown to precipitate 125I-labeled gp120. The MAbs therefore define carbohydrate structures expressed by the viral envelope glycoprotein gp120, indicating that glycans of the viral envelope are possible targets for immunotherapy or vaccine development or both.

Deuterium D(V/K) isotope effects on ethanol oxidation in hepatocytes: importance of the reverse ADH-reaction

The kinetic deuterium isotope effect, D(V/K), on ethanol oxidation was measured on hepatocytes from rat and pig by the radiometric competitive method using 14C-labelled ethanol containing deuterium in the (1-R)-position. The corrected D(V/K) values of 2.68 and 2.80 for rat and pig hepatocytes respectively were significantly different, suggesting differences in the amount of non-ADH ethanol oxidizing activity. The apparent isotope effects declined rapidly with time when acetaldehyde was present in the medium as a result of the reduction to ethanol of the [14C]-acetaldehyde formed from the double labelled ethanol by alcohol dehydrogenase (ADH). Fructose and cyanamide caused the acetaldehyde concentration during ethanol oxidation to increase by entirely different mechanisms, and the isotope effect to decrease with time, as did also the addition of acetaldehyde. The apparent first order rate constant for the reverse ADH reaction, assuming the reactants to be acetaldehyde and the ADH-NADH complex, was determined by two methods giving comparable results. In the presence of semicarbazide, which removes acetaldehyde, the isotope effect was nearly constant. This was the case also when the acetaldehyde concentration was very low (less than 1 microM) for other reasons, as in hepatocytes from starved animals. A mathematical formula describing the expected decrease of the apparent isotope effect with time was derived. The different response of pig and rat hepatocytes to addition of fructose (the 'fructose effect') is suggested to be caused by differences in activity of aldehyde dehydrogenases in the two species.

Marketing alternatives for hospitals to the nursing crisis

The current nursing shortage problem as defined in this article, is the result of a supply and demand imbalance. The demand for nurses is growing at a faster rate than the supply. If strategies are not implemented to correct this imbalance the demand for nurses will continue to surpass the supply, negatively affecting access to and delivery of quality patient care. Factors contributing to the increased demand for nurses and the dwindling supply must be examined if solutions to the problem are to be found and implemented. Factors contributing to the growing demand for nurses include the decreasing use of ancillary personnel by hospitals in an effort to tighten their budgets; the impact of Medicare's prospective payment system on hospital lengths of stay; the increase in patient acuity with advances in medical technology; and alternative health care opportunities pulling nurses away from the hospital setting. The supply of RNs is shrinking in relation to demand because of low retention rates; declining nursing school enrollment; non-competitive wages; poor working conditions; alternative career opportunities for women; and the lack of power and support within the nursing profession. An active marketing approach that relies on this assessment of contributing factors has been formulated in an attempt to resolve the problem and meet the increasing demand. Recommendations have been made and ranked in the order of their priority and pros and cons established for each. The strategies developed have been divided into four basic marketing categories of product, price, place, and promotion. If the problem is to be resolved these strategies must be marketed to hospitals, their administrators, nurses, other allied health professionals, third party payors, educators, and the general public. The nursing profession itself must find the unity and strength within its own group of professionals to build political and economic powers to enhance their product. Nursing is at a crossroad. Much depends on how we cope with the current shortage and its related issues. Nurses have the opportunity to shape their future. Hopefully, with proactive strategies, the profession will transform from a passive role to an active, vital force of the health care environment. The authors believe that through our marketing approaches this can be accomplished.

A randomised prospective study of treatment of non-ischaemic central retinal vein occlusion by isovolaemic haemodilution

In a randomised study 25 patients over 50 years of age with non-ischaemic central retinal vein occlusion (CRVO) were assigned to either a treatment (14 patients, isovolaemic haemodilution) or a control group (11 patients, no treatment). After three months eight eyes in patients with haemodilution improved, whereas none of the untreated eyes had better visual acuity (p less than 0.01). Thirteen haemodiluted and 11 control patients could be observed for one year. Six eyes of the haemodiluted patients retained a better visual acuity, whereas no improvements had occurred in the control group (p less than 0.025). In fluorescein angiography the lowering of the packed cell volume to 35-32% accelerated the time of maximal venous filling (tmvf) from 17.4 (SEM 1.4) s to 11.4 (SEM 0.9) s (p less than 0.005). In patients with non-ischaemic CRVO without treatment the passage time did not change. The shortened tmvf reflects a higher blood velocity. Thus isovolaemic haemodilution improves the visual prognosis in non-ischaemic CRVO probably by inducing a higher blood fluidity, which results in higher blood velocity, at least in areas of compromised retinal microcirculation.

Deuterium isotope effects as a tool in the study of ethanol oxidation in rat liver microsomes

The apparent kinetic deuterium isotope effect (I) on the oxidation of ethanol to acetaldehyde by washed rat liver microsomes was measured with (1-R)-[1-2H2, 1-14C]-ethanol (I1) and [1-2H2, 2-14C]-ethanol (I2) as substrates by a competitive technique involving only measurements of radioactivity. The average values were for non-induced rats, I1 = 1.57 and I2 = 2.23. When these two substrates were used with stereospecific enzymes (alcohol dehydrogenase and catalase) a small secondary effect was observed, causing I2 to be about 10% higher than I1. With non-stereospecific systems I2 was much larger than I1, and the values were connected by a simple formula. This relation in combination with use of the inhibitors, sodium azide and thiourea, made it possible to calculate tentatively the contribution to microsomal ethanol oxidation of catalase, a non-identified stereospecific enzyme, and non-stereospecific catalytic systems, as well as the isotope effects of the latter two systems. Measurements were made in microsomes from normal, phenobarbital treated, and acetone treated rats. For the stereospecific component an isotope effect of 1.4-1.5 was calculated for all three groups. For the non-stereospecific enzyme in acetone treated rats a value of 4.0 was found. Both the other groups showed a value about 2.7. The activity of the non-stereospecific system was about twice the normal in barbiturate treated, and 3 times the normal in the acetone treated group, where it contributed 70% of the total activity. The isotope effects on the changes in ethanol oxidation (the 'differential isotope effect') caused by inhibitors and activators were utilized to decide whether inhibitors were specific for a single reaction. Thus azide while inhibiting catalase completely, also inhibited other reactions. The large increase (5-6 times) in rate caused by Fe-ESDTA has an I2 of 1.6, equal to that for oxidation of ethanol by hydroxyl radicals.

Effect and compatibility of isovolaemic haemodilution in the treatment of ischaemic and non-ischaemic central retinal vein occlusion

In a prospective study, 48 eyes with non-ischaemic and 35 with ischaemic central retinal vein occlusion (CRVO) were treated by isovolaemic haemodilution (IHD). Two or more cardiovascular risk factors were present in 42% of patients with non-ischaemic and in 69% of patients with ischaemic CRVO (p less than 0.025). Nevertheless, IHD in no case caused serious cardiovascular complications. Minor problems were short fainting spells in 5% and a general weakness in 16% of the haemodiluted patients. The effect of IHD was measured by determining the time of maximal venous filling (tmvf) in fluorescein angiographies. Lowering the packed cell volume to 32-35% accelerated the tmvf from 18.4 +/- 1.61 to 13.1 +/- 1.0 s (p less than 0.001) in eyes with non-ischaemic CRVO and from 24.5 +/- 1.2 to 14.8 +/- 1.3 s (p less than 0.001) in eyes with ischaemic CRVO. After 3 months, an increase in visual acuity had occurred in 27% of eyes with non-ischaemic CRVO and in 48.5% with ischaemic CRVO. These improvement rates could nearly be maintained after 1 year. 59% of eyes with non-ischaemic and 25% with ischaemic CRVO were able to read (visual acuity greater than or equal to 6/15) after 1 year.

[Initial diagnosis of acquired immunologic deficiency syndrome (AIDS) by the ophthalmologist]

The authors report on two patients who presented with sudden loss of vision, due to irodocyclitis and retinochoroiditis in one patient and optic neuritis in the other. AIDS was diagnosed in both patients on the basis of a positive HIV antibody assay, lymphopenia, and a reduced helper-to-suppressor subset ratio. Soon afterwards, the patient with retinochoroiditis developed the full-blown picture of AIDS with cerebral involvement. Neither anticytomegaly treatment with DHPG nor triple therapy for toxoplasmosis was able to prevent the fatal course. The patient died within six months. In contrast, the patient with optic neuritis recovered full visual acuity. So far there has been no relapse, nor any opportunistic infection in other organs.

[Combination of phacoemulsification and trabeculectomy. Results of a retrospective study]

Combined trabeculectomy and phacoemulsification was performed on 21 eyes with poorly controlled glaucoma (15 open-angle glaucomas, 5 capsular glaucomas, and one secondary glaucoma) and coexisting cataract. In 20 of these eyes there was severe glaucomatous damage of the optic nerve with visual field loss. With the procedure used by the present authors there was a higher incidence of choroidal detachments, whereas other complications occurred at a lower rate than reported by other authors combining cataract extraction and trabeculectomy. Mean IOP was lowered from 25.7 +/- 6.1 to 17.1 +/- 3.2 mmHg after 18 months. Thirteen patients (62%) required no medication, while 5 (24%) required additional therapy for sufficient control of IOP (less than or equal to 21 mmHg). The results indicate that the combined phacoemulsification and trabeculectomy procedure may be a useful approach in eyes with severe glaucomatous damage and cataract.

Continuous monitoring of body temperature in pigs using non-invasive ear canal sensors

Monitoring of the body temperature in animals kept under intensive production conditions is desirable for a number of reasons: oestrus detection, disease monitoring and stress indication in addition to more specific needs, such as the selection of breeding pigs resistant to malignant hyperthermia and for various research purposes.

A randomised prospective study on treatment of central retinal vein occlusion by isovolaemic haemodilution and photocoagulation

Thirty eight patients with ischaemic and non-ischaemic central retinal vein occlusion were evaluated for the effect of isovolaemic haemodilution. They were allocated at random to a haemodilution group (19 patients, panretinal photocoagulation and isovolaemic haemodilution) and a control group (19 patients, panretinal photocoagulation). Haematocrit was lowered in steps to 30 to 35% in the haemodilution group by repeated exchanges of whole blood for plasma and dextran (MW 40 000) and kept at this level for a period of six weeks. The haemodilution did not lead to serious complications. Three months after starting the treatment eight of 19 patients with haemodilution showed a better visual acuity, whereas only one of 19 control patients had improved. Seven of 17 patients with haemodilution, but only one of 17 control patients, retained a better visual acuity after one year. In the haemodilution group there were fewer patients with macular fibrosis and more with only minor foveal changes. The haemodilution seems to be more effective in patients with ischaemic than with non-ischaemic central retinal vein occlusion. It is concluded that isovolaemic haemodilution improves the visual outcome of patients with central retinal vein occlusion, probably mediated by enhanced retinal blood flow.

Relationship between peritubular membrane potential and net fluid reabsorption in the distal renal tubule of Amphiuma

Amphiuma kidneys were isolated and perfused with modified Ringer solution and peritubular and transepithelial membrane potentials (p.d.s) in distal tubules measured with micro-electrodes during rapid changes of luminal electrolyte concentrations. Peritubular membrane potential and net fluid reabsorption (split-oil-droplet method) were also measured with and without application of various drugs known to alter transport. Raising the luminal sodium concentration from 10 to 100 mM reversibly increased the peritubular p.d. The magnitude of the peritubular p.d. was a saturable function of luminal sodium concentration. In the presence of chloride in the lumen the peritubular hyperpolarization following increased luminal sodium could be inhibited by luminal amiloride (10(-4)M). Sodium-induced hyperpolarization of the peritubular p.d. could be completely inhibited by 10(-5)M-ouabain. Adding amiloride (10(-4)M) to the luminal fluid rapidly and reversibly depolarized the peritubular p.d. and inhibited fluid reabsorption. Addition of amphotericin B (20 micrograms/ml) to the luminal perfusion solution had no effect on peritubular p.d. at 100 mM-luminal NaCl but at 10 mM-NaCl, peritubular p.d. hyperpolarized. Fluid reabsorption was stimulated (with 100 mM-NaCl in the lumen). Addition of amphotericin when the tubule was perfused on both sides with solutions containing a constant potassium concentration of 78 mM and a variable sodium concentration ranging from 7.8 to 34.5 mM revealed strong dependence of the peritubular hyperpolarization on the sodium concentration. Luminal furosemide (10(-4)M) and chlorothiazide (10(-4)M) and peritubular ethacrynic acid (10(-4)M) all reduced fluid reabsorption but hyperpolarized the peritubular p.d. The data suggest the presence of an electrogenic sodium transport process in the peritubular membrane that directly contributes to the generation of the peritubular potential. In addition, chloride transport has an important role in determining this potential.

Effect of calcium, furosemide and chlorothiazide on net volume reabsorption and basolateral membrane potential of the distal tubule

In the distal tubule of the isolated kidney of Amphiuma net volume reabsorption (split-oil droplet method) and basolateral membrane potential (psi b) were measured. Luminal perfusion solution could be changed rapidly from 108 mmol . 1-1 NaCl plus 0.1 mmol . 1-1 calcium to solutions containing 103 or 97 mmol . 1-1 NaCl plus 3.6 or plus 7.2 mmol . 1-1 calcium. Furthermore, 10(-4) mol . 1-1 furosemide or chlorothiazide were applied luminally. (1) Addition of 7.2 mmol . 1-1 calcium hyperpolarized psi b from -73.4 mV to -108.3 mV and inhibited net volume reabsorption. (2) Similarly, when furosemide was injected, psi b was hyperpolarized and net volume reabsorption reduced. Application of both high calcium and furosemide further inhibited volume reabsorption. (3) The effects of chlorothiazide were similar to those of furosemide. However, when both high calcium and chlorothiazide were administered psi b and volume reabsorption were almost normalized. (4) The data are consistent with the hypothesis that calcium and the diuretics interfere primarily with chloride uptake across the luminal membrane and thus reduce sodium chloride transport. When chlorothiazide in the presence of high luminal calcium almost normalized chloride transport, it is likely that its effects were by stimulating calcium transport and thus increasing intracellular calcium activity.

The effects of extracellular potassium, ouabain, and prostaglandins on intracellular potassium activity in sheep cardica Purkinje fibers

(1) Intracellular K activity (aKi) of sheep heart Purkinje fibers was measured using K-selective microelectrodes (liquid ion exchanger). aKi in the resting state with an extracellular K of 4 mmol . l-1 EK was 112.9 +/- 6.1 mmol . l-1 (n = 47) for a membrane potential (VM) of -73.3 +/- 0.9 mV. VM deviated from the calculated potassium equilibrium potential (EK = -93mV). (2) When extracellular K was decreased to 2 mmol . l-1 or increased to 6 and 10 mmol . l-1 EK changed from -114 to -84 and -73 mV, with little change in aKi. (3) aKi and VM significantly decreased after administration of 10(-6) mol . l-1 ouabain. (4) Prostaglandins (PGI2 10-100 micrograms . l-1 and PGE2 0.01-1 microgram . l-1) decreased aKi without greatly changing VM. The differences between VM and EK became smaller. These effects indicate an increase in K permeability and may explain the antiarrhythmic action of prostaglandins.