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High‐Affinity Calcium Binding in Rat Synaptosomal Plasma Membranes: Decrease in Young, Genetically Hypertensive Rats
Author(s) -
Nunez AnneMarie,
Devynck MarieAude,
Meyer Philippe
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb07911.x
Subject(s) - calcium , membrane , dissociation constant , chemistry , ionophore , endocrinology , synaptosome , medicine , free nerve ending , biophysics , mole , binding site , dissociation (chemistry) , pathogenesis , biochemistry , receptor , biology
A large number (about 4‐5 nmoVmg of protein) of high‐affinity (apparent dissociation constant at 37°C: K D37°C = 5 × 10 −8 M ) calcium binding sites was characterized in synaptosomal membrane fractions enriched in plasma membranes that were isolated from rat brain. These sites were studied simultaneously in membranes from spontaneously hypertensive young rats (SHR) and their normotensive controls. No difference was observed between whole synaptosomes from these two substrains. However, plasma membraneenriched fractions from SHR exhibited a reduced calcium binding capacity without a significant change in affinity. This decrease which averaged 15‐20% was not due to any variation in the accessibility of calcium to its binding sites, as similar results were obtained in the presence of the calcium ionophore A23,R7. The reduction found in calcium binding is very similar to that previously described in erythrocyte membranes. It is envisaged that such an abnormality at nerve endings might play a role in the pathogenesis of genetic hypertension.