GFA Content, Glutamate Uptake and Activity of Glutamate Metabolizing Enzymes in Differentiating Mouse Astrocytes in Primary Cultures

Abstract

The effects on GFA content, glutamate uptake and activity of glutamate metabolizing enzymes (glutamine synthetase, glutamate dehydrogenase, glutamate-oxaloacetate transferase) by three variables, i.e., length of culturing period, presence or absence of serum, and presence or absence of dibutyryl cyclic AMP (dBcAMP) were studied in primary cultures of astrocytes from newborn mice. During 3 weeks of culturing the content of GFA, the rate of glutamate uptake and the activity of all three enzymes increased but the period of maximum increase differed between the different parameters. The GFA content and the V_max and K_m for glutamate uptake were increased by dBcAMP and decreased by serum withdrawal but the enzyme activities were relatively little affected.

Astrocytic Adrenoceptors: A Major Drug Target in Neurological and Psychiatric Disorders?

“…An autoradiographic study showed that all individual cells in these cultures expressed β-adrenergic receptors [149]. In homogenates of our own highly purified mouse astrocytes, which contaiñ 300 pg of protein per cell [150], the specific binding of dihydroalprenolol amounts to 35 femtomol/mg protein or 2.1 x 10 10 molecules/mg protein [151], suggesting a binding density of ~6,500 β-adrenergic receptors per cell. The same cells produce ~150 pmol cAMP per min per mg protein [152], indicating a turnover of the adenylyl cyclase of 70/sec, i.e., the same value as calculated for glioma cells by Maguire et al [143].…”

Brain Primary Cultures and Vibrodissociated Cells as Tools for the Study of Astroglial Properties and Functions

“…In in vitro and even in some in vivo experimental setups the astrocytes have been shown to be coupled to signal transduction systems and effector systems such as energy metabolism, membrane potential and cell volume regulation [Kimelberg, 1991;Magistretti et al, 1993;Hansson, 1994;Hansson et al, 1997]. Furthermore, the astrocytes have a prominent capacity for glutamate clearance from the extracellular space [Hertz et al, 1978;Hansson and Rönnbäck, 1991;Blitzblau et al, 1996]. It can also be assumed that in addition to neurons, astrocytes are targets for noradrenaline and 5-HT transmission [Stone and Ariano, 1989;Christenson et al, 1991;Ridet et al, 1993;Hansson, 1997].…”

“…These factors have been taken into special consideration by Booher and Sensenbrenner [1972], who developed dissociation techniques which make it possible to separate glial precursor cells from neuronal cells. As a result of this, glial cells can be maintained in primary cultures for long periods of time, although alterations due to the absence of neurons should always be considered [Booher and Sensenbrenner, 1972;Schousboe et al, 1976;Hertz et al, 1978;McCarthy and de Vellis, 1980;Hallermayer et al, 1981;Pelton et al, 1981;Hansson, 1988]. In general, culture media must be supplemented with complex, and yet poorly defined, biological fluids such as fetal or adult sera, embryonic extracts and ascitic fluid to support these neural cultures.…”

“…Treatment of the cell cultures with dibutyryl-cyclic AMP caused cultured astrocytes to change from flat cells to retracted process-bearing cells [Moonen et al, 1976;Kimelberg et al, 1978;Hertz et al, 1978;Hansson, 1984;Ferrier et al, 1994]. Even physiological alterations have been observed [Ferroni et al, 1995].…”

Effect of Antidepressants on ATP Content, ³H-Valine Incorporation and Cell Morphometry of Astrocytes Cultured from Rat Brain

“…1995 a crucial role in the regulation of neuronal synaptic func tion but the literature on ATP concentration in neurons and astrocytes cultured in vitro is limited [5,6], It is also known that astrocytes grown in primary cul tures assume a flat epithelioid morphology [7,8]. The addition of dibutyryl-cyclic adenosine monophosphate (dB-cAMP) to cultured astrocytes induces several changes, the most obvious being morphological transfor mation from a flat, polygonal cell into a process-bearing, stellate cell type [9][10][11][12], The morphological transforma tion is accompanied by significant biochemical changes including ion channel expression [13,14], enzyme activ ities [15,16], metabolic changes [17] and altered expres sion of cell surface receptors [18,19], Astrocytes in primary culture have been shown to have (3-adrenergic receptors, the activation of which results in a large increase in cell c-AMP content [20][21][22], The role of the (3-receptors is of interest in rela tion to the mode of action of antidepressant drugs [23][24][25][26], Chronic exposure of cultured astrocytes to antidepressants affects |3-receptor-stimulated c-AMP responses. However, reports on direct effects of the exposure are inconsistent [27], It has recently been shown that antidepressants (e.g.…”