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Effects of Ca2+ Channel Blockers on Ca2+ Translocation Across Synaptosomal Memb...
Carvalho, C. A. M.; Coutinho, O. P.; Carvalho, A. P.The binding of [3H]nimodipine to purified synaptic plasma membranes (SPM) isolated from sheep brain cortex was characterized, and the effects of nimodipine, nifedipine, and (+)-verapamil on the [3H]nimodipine binding were compared to the effects on 45Ca2+ translocation under conditions that separate 45Ca2+ fluxes through Ca2+ channels from 45Ca2+ uptake via Na+/Ca2+ exchange. [3H]Nimodipine labels a single clas...
Effect of Monovalent Cations on Na+/Ca2 Exchange and ATP-Dependent Ca2+Transpor...
Coutinho, O. P.; Carvalho, A. P.; Carvalho, C. A. M.Two Ca2+ transport systems were investigated in plasma membrane vesicles isolated from sheep brain cortex synaptosomes by hypotonic lysis and partial purification. Synaptic plasma membrane vesicles loaded with Na+ (Na+i) accumulate Ca2+ in exchange for Na+, provided that a Na+ gradient (in2192out) is present. Agents that dissipate the Na+ gradient (monensin) prevent the Na+/Ca2+ exchange completely. Ca2+ accumu...
EFFECT OF TEMPERATURE AND IONOPHORES ON THE PERMEABILITY OF SYNAPTOSOMES
Carvalho, C. A. M.; Carvalho, A. P.Synaptosomes swell rapidly in isosmotic solutions of glycerol or urea, but the swelling in solutions of larger non-electrolytes, such as erythritol, glucose or sucrose is slower. The permeability of synaptosomes to non-electrolytes is temperature dependent, and the low activation energies for the permeation of urea (13 kcal/mol) and erythritol (9.5 kcal/mol) indicate that the penetration of non-electrolytes int...
Chlorotetracycline As An Indicator Of The Interaction Of Calcium With Brain Mem...
Carvalho, C. A. M.The fluorescence of chlorotetracycline (CTC) in the presence of synaptosomes isolated from sheep brain is selectively increased by Ca2+ under conditions in which Mg2+, Na+, K+, Li+ or choline have only a small effect. The monovalent cations release bound Ca2+ from synaptosomes, and this effect is reflected by a decrease in the CTC fluorescence. Under optimal conditions there is a near parallelism between Ca2+ a...
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