Abstract
The three-compartment model of brain acid-base regulation postulates that under circumstances of changing function or disease, hydrogen ion concentrations may differ considerably in the interstitial space (ISS), the neurons and the glial cells. During hyperglycemia plus profound ischemia, for example, direct measurements by microelectrodes followed by intracellular HRP staining show that intraglial pH can fall transiently as low as 3.9, although more often the nadir drops to the 4.5–5.5 range. Concurrently, ISS-pH and, by calculation, neuronal pH falls to and remains constant (but not necessarily the same) at pH 6.2. By contrast, during spreading depression, ISS and intraglial pH at first move rapidly and transiently in opposite directions, ISS [H+] rising, intraglial falling. These two then gradually stabilize, whereas neuronal pH remains substantially more steady and near normal, shifting only minimally from resting baseline levels over several minutes’ time. Similar but less pronounced effects follow direct electrical stimulation. The net change represents complex biophysical transmembrane and buffering mechanisms that appear to guard neuronal homeostasis.
Studies carried out on embryonic rat forebrain neurons and glia show that these cells have considerably different vulnerabilities to extracellular acidity depending on the anionic nature of the acid in the bathing medium. In cultures to which HCI was added to the medium, neurons and neuronal processes almost all survived ten minute exposures to pH 3.8, whereas glial cells succumbed after ten minute exposures at pH not lower than 4.2. Both types of cells, however, showed much greater vulnerability to lactic acidification in the media; neither neurons nor glia survived exposure for ten minutes at pH 4.8 or for sixty minutes at the lesser degree of acidity of 5.2. Measurements of intracellular pH in cultured mammalian neurons using the fluorescent dye BCECF demonstrated a rapid fall in intracellular pH from 7.18 to 6.80 when 20 mM lactate was added to pH — clamped extracellular medium held at a pH of 7.35. By contrast, when the pHo in the medium fell from 7.35 to 6.65 in the presence of 20 mM lactate, pHi fell to 6.48 and failed to recover unless pHo was quickly restored to 7.35 and lactate was removed from the medium. The findings indicate that CNS cell membranes are substantially more permeable to lactic acid compared to unorganic acids and that the vulnerability relates to the greater capacity of the former to induce a profound and rapid intracellular acidification.
Supported by Deutsche Forschungsgemeinschaft.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Petito CK, Babiak T (1982) Earlyproliferative changes in astrocytes in post-ischemic, non-infarcted rat brain.Ann Neurol 11: 510–518
Petito CK, Pulsinelli WA, JacobsonG, Plum F (1982) Edema and vascular permeability in cerebral ischemia:comparison between neuronal damage and infarction. J Neuropath Exp Neurol 41:423–436
Plum F (1983) What causesinfarction in ischemic brain. Neurology 33: 222–233
Pulsinelli WA, Brierley JB,Plum F (1982) Temporal profile of neuronaldamage in a model of transient forebrainischemia. Ann Neurol 11: 491–498
Kraig RP, Pulsinelli WA, Plum F(1985) Hydrogen ion buffering during complete brain ischemia. Brain Research342: 281 – 290
Kraig RP, Pulsinelli WA, Plum F(1986) Carbonic acid buffer changes during complete brain ischemia. Am JPhysiol 250 (Regulatory Physiol 19): R348–R357
Kraig RP, Nicholson C (1987)Profound acidosis in presumed glia during ischemia. In: Raichle M, Powers WV(eds) Cerebrovascular diseases. Raven, New York, pp 97–102
Kraig RP, Chesler M (1988) Dynamicsof volatile buffers in brain cells during spreading depression. In: Somjen G(ed) Cerebral hypoxia and stroke: reversible and irreversible effects and theirprevention. Plenum, New York, pp 279–289
Kraig RP, Chesler M (1988) Glialacid-base homeostasis in brain ischemia. In: Norenberg M, Hertz L, Schousbou N(eds) The biochemical pathology of astrocytes. Liss, New York, pp 365–376
Chesler M, Kraig RP (1987)Intracellular pH of astrocytes increases rapidly with corticalstimulation. Am J Physiol 253 (Regulatory Physiol 22): R666–R670
Ahmed Z, Connor JA (1980)Intracellular pH changes induced by calcium influx during electricalactivity in molluscan neurons. J Gen Physiol 75: 403–426
Enders W, Ballanyi K, Serve G, Grafe P (1986) Excitatory aminoacids and intracellular pH in motor neurons of the isolated spinal cord. NeurosciLett 72: 54–58
Ballanyi K, Grafe P, tenBruggencate G (1987) Ion activities and potassium uptake mechanisms of glialcells in guinea pig olfactory cortex slices. J Physiol (Lond) 382: 159–174
Nedergaard M, Kraig RP, Tanabe J,Pulsinelli WA (1988) Focal brain ischemia reverses the normalinterstitial/intracellular pH ratio. Neuroscience (Abstr) 14: 1065
Kraig RP, Petito CK, Plum F,Pulsinelli WA (1987) Hydrogen ions kill brain at concentrations reached inischemia. J Cereb Blood Flow Metabol 7: 379–386
Goldman S, Pulsinelli WA, Clarke W,Kraig RP, Plum F (1989) The effects of extracellular acidosis on neurons andglia in vitro.J Cereb Blood Flow Metabol 9: 471–477
Nedergaard M, Goldman SA,Pulsinelli WA (1989) Lactic acid induced intracellular acidification in primarycultures of mammalian brain. J Cereb Blood Flow Metabol 9: S 384
Nedergaard M, Goldman SA, Desai S,Pulsinelli WA (1989) Carrier mediated transport of lactic acid in culturedneurons and astrocytes. Neuroscience (Abstr) 15FF9O
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1993 Springer-Verlag
About this paper
Cite this paper
Plum, F. (1993). In vivo and in vitro Control of Acid-Base Regulation of Brain Cells During Ischemic and Selective Acidic Exposure. In: Baethmann, A., Kempski, O., Schürer, L. (eds) Mechanisms of Secondary Brain Damage. Acta Neurochirurgica, vol 57. Springer, Vienna. https://doi.org/10.1007/978-3-7091-9266-5_9
Download citation
DOI: https://doi.org/10.1007/978-3-7091-9266-5_9
Publisher Name: Springer, Vienna
Print ISBN: 978-3-7091-9268-9
Online ISBN: 978-3-7091-9266-5
eBook Packages: Springer Book Archive