Synaptosomal calcium uptake systems: prostaglandins are probably not involved in the regulation of calcium fluxes into and within the nerve endings.
45Ca2+ uptake measurements were performed on intact and osmotically lysed synaptosomes from rat brain to study the possible influence of prostaglandins (PGs) on Ca2+ movements into and within the nerve endings. The K+-induced 45Ca2+ uptake of intact synaptosomes was not influenced by several inhibitors of PG synthesis. 45Ca2+ uptake in lysed synaptosomal preparations was promoted by ATP and seemed to be largely attributable to mitochondria, as it was inhibited by mitochondrial poisons. This Ca2+ uptake was strongly reduced by PG synthesis inhibitors but also by PG precursor fatty acids. Both PG synthesis inhibitors and precursors, according to their relative efficacy in blocking Ca2+ uptake, were able to induce Ca2+ efflux from preloaded intrasynaptosomal organelles. The PGs E2, F2 alpha, D2, and thromboxane B2 were without effect on 45Ca2+ uptake in lysed synaptosomal preparations. On the basis of our results it does not seem likely that PGs influence Ca2+ availability by modulating Ca2+ fluxes into or within the nerve endings. The observed inhibitory effects of PG synthesis inhibitors and precursors on the intrasynaptosomal Ca2+ uptake might be due to unspecific impairment of mitochondrial functions.
D019297:2,4-Dinitrophenol; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001386:Azides / Q000494:pharmacology; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004140:Dinitrophenols / Q000494:pharmacology; D005227:Fatty Acids / Q000494:pharmacology; D005260:Female; D007038:Hypotonic Solutions; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009411:Nerve Endings / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D011453:Prostaglandins / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D019810:Sodium Azide; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D001386:Azides; D004140:Dinitrophenols; D005227:Fatty Acids; D007038:Hypotonic Solutions; D009840:Oligomycins; D011448:Prostaglandin Antagonists; D011453:Prostaglandins; D000255:Adenosine Triphosphate; D019810:Sodium Azide; D019297:2,4-Dinitrophenol; D002118:Calcium