Na-K Adenosine Triphosphatase Research Articles

Porcine glucagon-like peptide-2 microspheres ameliorate inflammation in lipopolysaccharide-challenged weaning piglets.

This study aimed to investigate the effects of porcine [gly2] glucagon-like peptide-2 (p[gly2]GLP-2) microspheres on lipopolysaccharide-challenged piglets and to evaluate efficacy of microspheres for administration compared with more conventional administration. Eighteen 21-d-old Duroc female piglets were randomly assigned into 3 groups: the control group (intraperitoneal injection with 3 mL saline solution daily), the glucagon-like peptide-2 (GLP-2) group (intraperitoneal injection with 3 mL p[gly2]GLP-2 at 20 nmol/kg BW daily), and the microsphere (MS) group (intraperitoneal injection with 100 mg p[gly2]GLP-2 microsphere suspension at Day 1). On Day 8, all piglets were injected with 100 μg lipopolysaccharide/kg BW. Results showed that administration of p[gly2]GLP-2 microspheres decreased the -lactic acid and methane dicarboxylic aldehyde content of the serum and increased the villus height and villus crypt ratio in the duodenum and ileum. Inducible nitric oxide synthase activity in the duodenum and ileum decreased, whereas enzyme activity for sucrose and Na-K adenosine triphosphatase in the ileum increased with treatment of p[gly2]GLP-2 microspheres. In the MS group, we observed downregulation of IL-8, TNF-α, IFN-γ, and GLP-2R mRNA expression in the ileum, upregulation of positive cell expression in the duodenum and positive cell expression in the ileum, and downregulation of GLP-2 receptor positive cell expression in the ileum. One injection of p[gly2]GLP-2 microspheres was as effective as p[gly2]GLP-2 administered for 7 d. Results suggested that p[gly2]GLP-2 can be a candidate agent for ameliorating weaning stress in piglets and that the use of microspheres is an ideal delivery system for GLP-2.

Electrolytes: The Salts of the Earth

What do you need to know as medical laboratory scientists when performing plasma electrolyte analysis? What new information should you consider regarding best laboratory practice in electrolyte analysis? This review article will answer some of these questions. Background In human physiology it is best to refer to electrolytes, the main component in bodily fluids, in the context of extracellular fluid (ECF) volume and total water (H 2 O) content in the body. Electrolytes are also best referenced collectively rather than individually because they are part of an integrated physiological mechanism of H 2 O and ionic balance. Thirst, renal function, and hormonal response help to maintain homeostasis of electrolytes. 1 These entities play a role in general functions of metabolic pathways, enzyme activation, acid-base balance, muscular-function regulation, and nervous-tissue contractions. Control of electrolyte levels is based on H 2 O and pH balance and is enacted by the renal glands through processes such as active transport in the proximal convoluted tubules, osmosis, and passive diffusion. At a cellular level, sodium (NA) and potassium (K) levels are maintained by the Na-K–adenosine triphosphatase (ATPase) pump. 1 The endocrine system influences the distal convoluted tubules via the renin-aldosterone system and the circulating levels of vasopressin and natriuretic peptides in bodily fluids.

INCREASED AEROBIC GLYCOLYSIS THROUGH β2 STIMULATION IS A COMMON MECHANISM INVOLVED IN LACTATE FORMATION DURING SHOCK STATES

During septic shock, muscle produces lactate by way of an exaggerated NaK-adenosine triphosphatase (ATPase)-stimulated aerobic glycolysis associated with epinephrine stimulation possibly through beta2 adrenoreceptor involvement. It therefore seems logical that a proportion of hyperlactatemia in low cardiac output states would be also related to this mechanism. Thus, in low-flow and normal-to-high-flow models of shock, we investigate (1) whether muscle produces lactate and (2) whether muscle lactate production is linked to beta2 adrenergic stimulation and Na+K+-ATPase. We locally modulated the adrenergic pathway and Na+K+-ATPase activity in male Wistar rats' skeletal muscle using microdialysis with nonselective and selective beta blockers and ouabain in different models of rodent shock (endotoxin, peritonitis, and hemorrhage). Blood flow at the probe site was evaluated by ethanol clearance. We measured the difference between muscle lactate and blood lactate concentration, with a positive gradient indicating muscle lactate or pyruvate production. Epinephrine levels were elevated in all shock groups. All models were associated with hypotension and marked hyperlactatemia. Muscle lactate concentrations were consistently higher than arterial levels, with a mean gradient of 2.5+/-0.3 in endotoxic shock, 2.1+/-0.2 mM in peritonitis group, and 0.9+/-0.2 mM in hemorrhagic shock (P<0.05 for all groups). Muscle pyruvate concentrations were also always higher than arterial levels, with a mean gradient of 260+/-40 microM in endotoxic shock, 210+/-30 microM in peritonitis group, and 90+/-10 microM in hemorrhagic shock (P<0.05 for all groups). Despite a decrease in blood flow, lactate formation was decreased by all the pharmacological agents studied irrespective of shock mechanism. This demonstrates that lactate production during shock states is related, at least in part, to increased NaK-ATPase activity under beta2 stimulation. In shock state associated with a reduced or maintained blood flow, an important proportion of muscle lactate release is regulated by a beta2 receptor stimulation and not secondary to a reduced oxygen availability.

Cultivated Corneal Endothelial Transplantation in a Primate: Possible Future Clinical Application in Corneal Endothelial Regenerative Medicine

To review our attempt to devise a method of cultivated corneal endothelial transplantation using primates in which corneal endothelium, like that of humans, has low proliferative ability. Monkey corneal endothelial cells (MCECs) were cultivated, with subcultures grown on collagen type I carriers. The corneal endothelia of 6 eyes of 6 monkeys were scraped intensively, after which cultivated MCEC sheets were inserted into the anterior chamber of 4 eyes. As controls, a collagen sheet without MCECs was transplanted in 1 eye of a monkey, and a suspension of cultivated MCECs was injected into the anterior chamber of 1 eye of another monkey. MCECs produced a confluent monolayer of closely attached hexagonal cells, which expressed both ZO-1 and Na-K adenosine triphosphatase. Early postoperative period MCEC sheets were attached to Descemet membrane, and corneal clarity was recovered. Six months after transplantation, MCEC-transplanted corneas remained clear, and closely attached hexagonal cells were observed. In 1 animal with longer observation, polygonal cells were observed by in vivo specular microscopy at a density of >2000 cells/mm2 and remained >1600 cells/mm2 for < or =2 years. Control eyes showed irreversible bullous keratopathy throughout the observation period. Cultivated MCECs become attached to the transplanted eye and maintain a clear cornea < or =2 years postoperatively, suggesting that corneal endothelial cells of primates might have proliferative ability in vivo once they have been cultured and proliferated in vitro. Our monkey model constitutes an important step forward for regenerative medicine with possible future application in patients with corneal endothelial dysfunction.

Influence of Hypoxia and Sex on Hyponatremic Encephalopathy

Over the past 20 years it has become increasingly apparent that hyponatremic encephalopathy is a major cause of inhospital morbidity and mortality, particularly in postoperative patients. The factors that may lead to death or permanent brain damage and the susceptible patient groups have been gradually elucidated. Hyponatremic encephalopathy most commonly leads to brain damage in young women and in prepubescent children. The causes of brain damage include brain edema, cerebral hypoxemia, decreased brain blood flow, increased intracranial pressure, and improper therapy. Cerebral hypoxia occurs through a combination of impaired brain adaptation and cerebral vasoconstriction. Brain adaptation consists largely of brain cell loss of sodium and potassium by means of the Na-K adenosine triphosphatase (ATPase) system. There is also loss of organic osmolytes. The brain Na-K ATPase system is impaired by a combination of vasopressin plus estrogen and is stimulated by testosterone. Similarly, vasopressin plus estrogen leads to cerebral vasoconstriction, resulting in a decrement of brain oxygen utilization and cerebral blood flow. Vasopressin also directly decreases brain production of ATP. The combination leads to hypoxic brain damage, which appears to be the major cause of brain damage associated with hyponatremic encephalopathy. Measurement of arterial P o 2 in patients with symptomatic hyponatremia usually demonstrates a P o 2 <50 mm Hg. Improper therapy is another possible cause of brain damage in patients with hyponatremic encephalopathy. The type and distribution of such lesions are similar to those found in patients with hyponatremic encephalopathy who have severe hypoxia. Current scientific knowledge indicates that patient survival can be improved through aggressive treatment of hypoxia associated with hyponatremic encephalopathy, particularly in young women.

Environmental distal renal tubular acidosis in Thailand: an enigma.

Distal renal tubular acidosis is a common health problem in northeastern Thailand, with the population background of the low potassium intake, low urine citrate, and decreased red blood cell Na-K adenosine triphosphatase (ATPase) activity and the environment of the high soil vanadium. The disease is usually seen in the people with low socioeconomic status in summer. The patients have decreased gastric acidity and low urine potassium. There are varying degrees of renal function from normal to impairment. Gastric hypoacidity is an important clue. Defects in H-K ATPase and anion exchange (AE2) mechanism are considered. The urine vanadium is higher in the patients than that of normal rural northeastern villagers. Inhibition of H-K ATPase by vanadium seems possible and requires more supporting evidence. AE1 gene mutation is noted in few patients. The cause of dRTA is not apparent. The AE2 gene and H-K ATPase gene remain to be studied. Both environmental and genetic factors could contribute to the pathogenesis of the disease.

Cytochemical study of ouabain-sensitive, K(+)-dependent p-nitrophenylphosphatase activity in guinea pig facial nerve.

The localization of ouabain-sensitive, K(+)-dependent p-nitrophenylphosphatase (K-NPPase) activity, the second dephosphorylative property of the Na-K adenosine triphosphatase complex, was cytochemically studied in the intra-temporal portion of the facial nerve in normal guinea pigs using a cerium-based method. A fine-granular reaction product of the K-NPPase activity was observed on the cytoplasmic side of the axolemma of the axon cylinder, of the incisures of Schmidt-Lanterman, and of the nodes of Ranvier. No reaction product was detected on the periaxonal and outermost plasma membrane of Schwann cells and in the myelin sheath. In control tissue samples, the enzyme activity was almost completely inhibited by 10 mM ouabain, and no reaction was noted in medium without K+.

Altered responses of aortic smooth muscle from Sprague-Dawley rats with salt-induced hypertension.

1. The contractile responses of aortic ring preparations from Sprague-Dawley rats made hypertensive by 6-week dietary salt loading were studied. The test and control diet contained 8.0 and 0.3% NaCl, respectively. Aortic rings from salt-loaded rats showed enhanced sensitivity to noradrenaline (NA) but not to serotonin. Contractile responses to CaCl2 in Ca-free NA-containing medium was significantly enhanced in salt-loaded rats, but was unchanged in K(+)-depolarised medium. K(+)-induced relaxation (a functional indicator of Na-K adenosine triphosphatase activity) was sensitive to 10 mumol/L ouabain and was significantly attenuated in aortic rings from salt-loaded rats. The results suggest that hypertension induced by salt-loading is associated with enhanced sensitivity to NA, increased Ca2+ entry through receptor-operated channels, and impairment of Na-K ATPase enzyme activity.

Research Note: Effects of Several Selected Odorants on the Sodium- and Potassium-Dependent Adenosine Triphosphatase Activities of Two Different Chicken Olfactory Turbinals

The NaK-adenosine triphosphatase (ATPase)-rich nerve-ending particle preparations (B fractions) of the epithelial tissue of chicken olfactory tubercle and the olfactory main concha were isolated by differential centrifugation. These tissues were exposed to the following odorants: 2-nonanone, 1-nonanol, 1-octanol, (+)2-octanol, and (−)2-octanol. There was a significant stimulation of NaK-ATPase by 2-nonanone (1 × 10–3M) in the B fraction of the olfactory tubercle and olfactory main concha. The NaK-ATPase increased significantly in the B fraction response of the olfactory main concha with 1 × 10–3M of 1-octanol but NaK-ATPase declined significantly in the presence of 1 × 10–3M of 1-nonanol. Both optical and structural isomers of odorants were shown to elicit different responses in NaK-ATPase activity. It is proposed that interactions between the odorant molecules and the membrane bound NaK-ATPase complex lead to recognition of odor by chickens.

Membrane isolation on polylysine-coated beads. Plasma membrane from HeLa cells.

HeLa cell plasma membranes have been purified after binding cells to polylysine-coated polyacrylamide beads. Cell attachment to beads and membrane recovery were maximal in a sucrose-acetate buffer, pH 5.0, at 25 degrees C. Measurements of ouabain-sensitive NaK-adenosine triphosphatase, membrane-bound 125I-wheat germ agglutinin, and chemical analyses showed that membranes on beads were of comparable or greater purity than membranes isolated by conventional methods. Because the isolation procedure is rapid (approximately 2.5 h), and produces membranes whose protoplasmic surfaces are fully exposed, it should be a useful supplement to standard isolation techniques.

Ouabain antagonism of noradrenaline inhibitions of cerebellar purkinje cells and dopamine inhibitions of caudate neurones

As a test of the hypothesis that catecholamines exert their inhibitory effects on neuronal activity via stimulation of an electrogenic ion pump, the ability of iontophoretically applied ouabain, a known inhibitor of neuronal Na-K adenosine triphosphatase, to antagonize noradrenaline and γ-aminobutyric acid inhibitions of Purkinje cells and dopamine and γ-aminobutyric acid inhibitions of caudate cells was examined. Ouabain exhibited antagonistic activity toward amine inhibitions on both types of cells while leaving the amino acid inhibition intact. The results are interpreted as being consistent with a “pump” hypothesis of catecholamine inhibition of neuronal excitability.