Energy Metabolism in Rat Brain Synaptosomes from Nembutal‐Anesthetized and Nonanesthetized Animals

Rafałowska, Urszula; Erecińska, Maria; Wilson, David F.

doi:10.1111/j.1471-4159.1980.tb11218.x

Cited by 62 publications

(18 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The synaptosomes are quite large, measuring -0.6-1.2 ,um in diameter (43) and contain approximately from zero to four mitochondria which on an average is -24% of the synaptosomal volume (43). The degree of contamination by free mitochondria in our synaptosomal preparation (Table I) is well within the limits observed by other investigators (16,44).…”

Section: Discussionsupporting

confidence: 79%

“…It also has been shown that there is a temporary decrease in oxygen consumption and ATP synthesis in synaptosomes both in starved rats subjected to 30 min of 7% oxygen (Po2 27.5 mmHg) and in anesthetized rats. However, these changes were normalized by feeding the animals before hypoxia or by returning them to a normal oxygen environment (44). From these observations it does not appear that the anesthesia contributed significantly to the alteration of the Na-K ATPase pump activity that we observed.…”

Section: Discussionmentioning

confidence: 52%

“…They were anesthetized for -20 min during which time their arterial Po2 went from 95 to 75 mmHg. Numerous investigators have studied the effects of anesthesia and hypoxia on synaptosomes of rat brain and have found no permanent alteration in the rate of oxygen consumption and energy use (44)(45)(46). It also has been shown that there is a temporary decrease in oxygen consumption and ATP synthesis in synaptosomes both in starved rats subjected to 30 min of 7% oxygen (Po2 27.5 mmHg) and in anesthetized rats.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Abnormal sodium transport in synaptosomes from brain of uremic rats.

Fraser¹,

Sarnacki²,

Arieff³

1985

J. Clin. Invest.

View full text Add to dashboard Cite

The causes of central nervous system (CNS) dysfunction in uremia are not well known and are not completely reversed by dialysis. This problem was investigated in synaptosomes, which are membrane vesicles from synaptic junctions in the brain. We measured Na uptake under conditions of control, veratridine stimulation, and tetrodotoxin inhibition, in synaptosomes from normal and acutely uremic (blood urea nitrogen, 250 mg/dl) rats. In the control state, maximal Na uptake was 2.2±0.2 and 1.9±03 nmol/mg of protein in normal and uremic synaptosomes, respectively. With veratridine stimulation, Na uptake was increased by 1.9 and 3.6 nmol/mg of protein in normal vs. uremic rats (P < 0.001). The increased veratridine-stimulated Na uptake observed in uremia could be due either to increased membrane permeability to Na or decrease in the Na-K ATPase pump activity. To investigate this, we studied the Na-K ATPase pump function by evaluating uptake of K (using rubidium as a tracer), uptake of Na during ATP stimulation, and inhibition of Rb and Na uptake by ouabain. In uremic rats both Rb uptake and ATP-stimulated Na uptake were significantly less than in normals (P < 0.005). This suggests a defect in the Na-K ATPase pump. Membrane permeability for Na was then evaluated both by measuring initial Na uptake, and with addition of valinomycin. No change in Na uptake pattern was observed with valinomycin, and initial Na uptake was not significantly different in normal versus uremic synaptosomes. These data show that (a) in uremic rats veratridine-stimulated Na accumulation is significantly greater than normal; (b) the increased Na accumulation observed in uremia appears to be due to alterations in Na-K ATPase pump activity, and (c) the

show abstract

Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Abnormal sodium transport in synaptosomes from brain of uremic rats.

Fraser¹,

Sarnacki²,

Arieff³

1985

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

“…Hyponatremia with normal arterial P02 resulted in a 22% mortality but the same degree of hyponatremia combined with modest hypoxia resulted in 100% mortality (Fig. 2) (23,30). The yield of synaptosomes from individual rat brains is inadequate to evaluate sodium transport via several different pathways.…”

Section: Rat Studies Effects Of Hypoxic Hypoxia and Hyponatremia On Mmentioning

confidence: 99%

Hypoxic and ischemic hypoxia exacerbate brain injury associated with metabolic encephalopathy in laboratory animals.

Vexler

Ayus²,

Roberts³

et al. 1994

J. Clin. Invest.

View full text Add to dashboard Cite

Hypoxemia is a major comorbid factor for permanent brain damage in several metabolic encephalopathies. To determine whether hypoxia impairs brain adaptation to hyponatremia, worsening brain edema, we performed in vitro and in vivo studies in cats and rats with hyponatremia plus either ischemic or hypoxic hypoxia. Mortality with hypoxic hypoxia was 0%; with hyponatremia, 22%; and with hyponatremia + hypoxia, 100%. Hyponatremia in cats produced brain edema, with a compensatory decrease of brain sodium. Ischemic hypoxia also resulted in brain edema, but with elevation of brain sodium. However, when ischemic hypoxia was superimposed upon hyponatremia, there was elevation of brain sodium with further elevation of water. Outward sodium transport in cat cerebral cortex synaptosomes was measured via three major pathways through which brain osmolality can be decreased. After hyponatremia, sodium transport was significantly altered such that brain cell osmolality would decrease: 44% increase in Na+-K+-ATPase transport activity (ouabain inhibitable); 26% decrease in amiloride-sensitive sodium uptake. The change in veratridine-stimulated sodium uptake was not significant (P > 0.05). When ischemic hypoxia was superimposed upon hyponatremia, all of the cerebral adaptive changes induced by hyponatremia alone were eliminated. Thus, hypoxia combined with hyponatremia produces a major increase in brain edema and mortality, probably by eliminating the compensatory mechanisms of sodium transport initiated by hyponatremia that tend to minimize brain swelling. (J. Clin. Invest. 1994.93:256-264.)

show abstract

“…We have succeeded recently in developing a preparation of synaptosomes (20)(21)(22)(23), based on the original procedure ofBooth and Clark (24), in which the values of energy parameters (20,21), concentration of intrasynaptosomal potassium (22), and transmembrane electrical potential (23) are very close to those in intact neurons. In view ofthe postulated function for the highaffinity GABA uptake system in neuronal transmission, we have examined our preparation of synaptosomes for this activity by 'using different and more sensitive methods for measuring GABA concentration.…”

mentioning

confidence: 99%

Net uptake of gamma-aminobutyric acid by a high-affinity system of rat brain synaptosomes.

Pastuszko¹,

Wilson²,

Erecińska³

1981

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Rat brain synaptosomes isolated on. discontin- 'using different and more sensitive methods for measuring GABA concentration. In this paper we show that synaptosomes carry out rapid net uptake of GABA and that this net-uptake occurs through a high-affinity system. Homoexchange is shown to account for less than 10% ofthe measured [14C]GABA uptake. MATERIALS AND METHODSMale Sprague-Dawley rats (180-220 g) were used throughout the study. Synaptosomes were isolated from the forebrains of rats essentially as described (24). The final synaptosomal pellet was suspended in Krebs-=Henseleit Hepes buffer (140 mM NaCl/5 mM KCV1.3 mM MgSO4/5 mM NaHCOj2.5 mM CaCl2/1 mM Tris phosphate/10 mM Tris Hepes, pH 7.4), containing 10 mM glucose.Synaptosomes, suspended at about 6 mg of protein per ml, were preincubated for 6 min with constant shaking at 250C. The uptake of GABA was measured in three different experimental systems after dilution of the incubation mixture in the Krebs-Henseleit Hepes buffer to a final protein concentration of 1-2 mg/ml (unless indicated otherwise). (i) The synaptosomal suspensions were supplemented with 2.4 AM [14C]GABA (Amersham: specific activity, 224 Ci/mol; 1 -Ci = 3.7 X 10'°b ecquerels), and the radioactivity of the supernatant and of the pellet was measured after rapid centrifugation (Beckman microfuge) of the aliquots of the incubation mixture through a layer of silicone oil (specific gravity 1.03) at appropriate time intervals. (ii) The synaptosomal suspension was supplemented with 2 ,uM nonradioactive GABA, and aliquots were centrifuged through silicone oil into a 3% (wt/vol) solution of perchloric acid. The supernatants were removed, acidified with perchloric acid (3% final concentration), and centrifuged. The perchloric acid-soluble fractions (i.e., synaptosomal pellets and postsynaptosomal supernatants) were diluted 1:2 in 50 mM citrate buffer (pH 2.0), and concentrations of GABA were measured in a Perkin-Elmer amino acid analyzer. (iii) Synaptosomes (5-6 mf of protein per ml) were preincubated for 6 min with 2 juM [ 4C]GABA and then diluted 1:10 into KrebsHenseleit Hepes buffer containing various concentrations of nonradioactive GABA (0-10 AM). Radioactivity was then measured in the supernatants and in the pellets at appropriate time intervals after separation of the synaptosomes from the medium by rapid centrifugation through silicone oil. Radioactivity was determined in a Searle Delta 300 liquid scintillation counter with aqueous counting scintillant (Amersham).Protein was measured by a biuret reaction, with bovine serum albumin as the standard. RESULTS AND DISCUSSIONRadioactive GABA was rapidly taken up by suspensions of synaptosomes, and the initial rate ofuptake was proportional to the protein concentration in the range 0.5-2 mg of protein per ml (Fig. 1). From the initial~linearrates ofGABA uptake at various external concentrations of this amino acid, kinetic constants were calculated by a double-reciprocal plot analysis of the results (Fig. 2). The'Km was found to be 6.25 ,AM a...

show abstract

Energy Metabolism in Rat Brain Synaptosomes from Nembutal‐Anesthetized and Nonanesthetized Animals

Cited by 62 publications

References 36 publications

Abnormal sodium transport in synaptosomes from brain of uremic rats.

Abnormal sodium transport in synaptosomes from brain of uremic rats.

Hypoxic and ischemic hypoxia exacerbate brain injury associated with metabolic encephalopathy in laboratory animals.

Net uptake of gamma-aminobutyric acid by a high-affinity system of rat brain synaptosomes.

Contact Info

Product

Resources

About