sodium-propionate and Acidosis

This study describes the use of a microperfusion system to create rapid, large regional changes in intracellular pH (pH(i)) within single ventricular myocytes. The spatial distribution of pH(i) in single myocytes was measured with seminaphthorhodafluor-1 fluorescence using confocal imaging. Changes in pH(i) were induced by local external application of NH(4)Cl, CO(2), or sodium propionate. Local application was achieved by simultaneously directing two parallel square microstreams, each 275 microm wide, over a single myocyte oriented perpendicular to the direction of flow. One stream contained the control solution, and the other contained a weak acid or base. End-to-end, stable pH(i) gradients as large as 1 pH unit were readily created with this technique. This result indicates that pH within a single cardiac cell may not always be spatially uniform, particularly when weak acid or base gradients are present, which can occur, for example, in regional myocardial ischemia. The microperfusion method should be useful for studying the effects of localized acidosis on myocyte function, estimating intracellular ion diffusion rates, and, possibly, inducing regional changes in other important intracellular ions.

Topics: Acidosis; Ammonium Chloride; Animals; Buffers; Carbon Dioxide; Cells, Cultured; Diffusion Chambers, Culture; Heart Ventricles; HEPES; Hydrogen-Ion Concentration; In Vitro Techniques; Microscopy, Confocal; Muscle Fibers, Skeletal; Myocardium; Perfusion; Propionates; Rabbits; Sarcolemma

The purpose of the present studies was to determine whether acidosis activates protein tyrosine kinase pathways. Incubation of MCT cells, a renal proximal tubule cell line, in acid media caused increased phosphotyrosine content of 60- to 70- and 120-kDa cytosolic proteins. Media acidification induced a twofold increase in c-Src activity that occurred within 30 s. Significant activation occurred with media pH changes as small as 0.07 pH unit accompanied by cell acidification of 0.06 pH unit. Sodium propionate addition, NH4Cl prepulse, and nigericin addition, maneuvers that decrease intracellular pH in the absence of changes in extracellular pH, activated c-Src. Significant activation by sodium propionate was seen with cell pH changes as small as 0.07 pH unit. Sodium orthovanadate, a protein tyrosine phosphatase inhibitor, prevented c-Src activation by media acidification but did not prevent protein tyrosine phosphorylation. In summary, decreased intracellular pH activates c-Src. Acid activation of c-Src represents a novel mechanism of c-Src activation that may be relevant to many cellular responses to acidosis.

Topics: Acidosis; Animals; Cell Line; Cytosol; Enzyme Activation; Kidney Tubules, Proximal; Mice; Phosphotyrosine; Propionates; Proto-Oncogene Proteins pp60(c-src); Vanadates

Three Na compounds were tested to determine which was best able to treat metabolic acidosis in dairy cows. Metabolic acidosis was induced in test cows by feeding a diet that was high in anions for 7 d before the administration of treatment on d 8. The orally administered treatments were equivalent amounts of Na in the form of NaCl (208.6 g), NaHCO3 (300 g), or Na propionate (343 g). The initiation of oral treatment was designated as time 0, and blood samples were taken 15 min before treatment, immediately before treatment, and 15, 30, 45, 60, 90, 120, 180, 240, 300, and 360 min after treatment. Before treatment, all cows were in a state of metabolic acidosis as was evidenced by low blood pH, low HCO3 concentrations, and high plasma Cl concentrations. After treatment, blood pH and HCO3 were markedly higher for cows receiving NaHCO3 and Na propionate but not for cows receiving NaCl. We concluded that orally administered NaHCO3 and Na propionate were equally effective in correcting the acid-base balance of blood, as was predicted by the strong ion difference theory of acid-base physiology. Sodium propionate may be considered a more effective treatment of metabolic acidosis in diseases such as ketosis because the added propionate can serve as a source of glucose for the cow.

Topics: Acidosis; Administration, Oral; Animals; Bicarbonates; Blood; Cattle; Cattle Diseases; Chlorides; Female; Hydrogen-Ion Concentration; Kinetics; Propionates; Sodium Bicarbonate; Sodium Chloride

Expression of major stress proteins is induced rapidly in ischemic tissues, a response that may protect cells from ischemic injury. We have shown previously that transcriptional induction of heat-shock protein 70 by hypoxia results from activation of DNA binding of a preexisting, but inactive, pool of heat shock factor (HSF). To determine the intracellular signals generated in hypoxic or ischemic cells that trigger HSF activation, we examined the effects of glucose deprivation and the metabolic inhibitor rotenone on DNA-binding activity of HSF in cultured C2 myogenic cells grown under normoxic conditions. Whole-cell extracts were examined in gel mobility shift assays using a 39-bp synthetic oligonucleotide containing a consensus heat-shock element as probe. ATP pools were determined by high-pressure liquid chromatography and intracellular pH (pHi) was measured using a fluorescent indicator. Glucose deprivation alone reduced the cellular ATP pool to 50% of control levels but failed to activate HSF. However, 2 x 10(-4) M rotenone induced DNA binding of HSF within 30 min, in association with a fall in ATP to 30% of control levels, and a fall in pHi from 7.3 to 6.9. Maneuvers (sodium propionate and amiloride) that lowered pHi to 6.7 without ATP depletion failed to activate HSF. Conversely, in studies that lowered ATP stores at normal pH (high K+/nigericin) we found induction of HSF-DNA binding activity. Our data indicate that the effects of ATP depletion alone are sufficient to induce the DNA binding of HSF when oxidative metabolism is impaired, and are consistent with a model proposed recently for transcriptional regulation of stress protein genes during ischemia.

Topics: Acidosis; Adenosine Triphosphate; Amiloride; Base Sequence; Cells, Cultured; DNA-Binding Proteins; Glucose; Heat-Shock Proteins; In Vitro Techniques; Molecular Sequence Data; Muscles; Oligodeoxyribonucleotides; Oxidative Phosphorylation; Propionates; Regulatory Sequences, Nucleic Acid; Rotenone; Transcription Factors

Propionate utilisation by the liver in spontaneously ketotic dairy cows was investigated by determining blood glucose levels after an intravenous sodium propionate load (2.5 mmol kg-1). In addition, blood ketone body concentrations were measured after propionate loading. Cows were divided into three groups (control, mildly ketotic and severely ketotic) by their blood acetoacetate concentrations. Plasma glucose concentrations increased significantly after sodium propionate injection in all three groups (P less than 0.05). The maximum glucose concentration occurred earlier in the control group than in the ketotic groups. Changes in glucose concentrations following propionate loading of control and ketotic cows differed significantly at 20 minutes and beyond. Differences in the change in glucose concentration between mildly ketotic and severely ketotic cows were not significant. Acetoacetate concentration was significantly decreased at five minutes and beyond after the injection in ketotic cows, whereas beta-hydroxybutyrate concentration decreased more slowly. A decrease in beta-hydroxybutyrate concentration was significant at 40 minutes and beyond in the severely ketotic group and at 10 minutes and beyond in the mildly ketotic group after loading.

Topics: 3-Hydroxybutyric Acid; Acetoacetates; Acidosis; Animals; Blood Glucose; Cattle; Cattle Diseases; Female; Hydroxybutyrates; Injections, Intravenous; Ketosis; Lactation; Liver; Liver Function Tests; Pregnancy; Propionates; Puerperal Disorders

Topics: Acidosis; Animals; Cattle; Cattle Diseases; Ketosis; Propionates