Measurement of Phospholipase C Activity in Brain Membranes
Besides the receptor/G, mechanism, PLC is readily stimulated by increases in the cytosolic concentration of calcium (5). Accordingly, a plethora of stimuli resulting in calcium entry (direct receptor gating, depolarization, and so forth) are expected to stimulate PLC in brain slices or other preparations, like synaptosomes or synaptoneurosomes. However, in membrane assays, there is no asymmetry in the calcium concentrations across the membrane, which are buffered down to resting intracellular levels. This features a clear difference between mechanisms of PLC activation involving the direct coupling receptor/G,-,/PLC (as muscarinic or serotonergic stimulation), on the one hand, and those involving calcium activation of the enzyme (such as a,-adrenergic, ionomycin, or KC1 stimulation), on the other hand, which will not result in PLC stimulation (Fig. 1).
KeywordsSodium Deoxycholate Agonist Effect Free Calcium Concentration Resuspension Buffer Phosphoinositide Hydrolysis
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