A. Ghassemi, D. S. Dhillon and P. Rosenberg. β-Bungarotoxin-induced phospholipid hydrolysis in rat brain synaptosomes: effect of replacement of calcium by strontium. Toxicon26, 509 - 514, 1988. - We tested whether, upon substitution of Ca2+by Sr2+in a medium containing β-bungarotoxin, sufficient Ca2+remained bound to the tissue to support phospholipid hydrolysis in rat brain synaptosomes. The phrenic nerve - diaphragm preparation could not be used, since replacement of Ca2+by Sr2+prolonged time to block of indirectly evoked contractions; however, no phospholipid hydrolysis could be detected (either in the presence of Ca2+or Sr2+), due to the small amounts of presynaptic terminals. Following initial exposure of synaptosomes to a Ca2+containing medium and then removal of Ca2+, incubation with β-bungarotoxin (1 or 10μg/ml) caused significant phospholipid hydrolysis whether or not Sr2+was present. Therefore, conclusions as to whether phospholipase A2activity is required for presynaptic actions of β-bungarotoxin cannot be derived from studies in which Sr2+is used to inhibit enzymatic activity. © 1988.
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