The inhibition of [3H] inositol 1,4,5‐trisphosphate binding by Ca2+ is modified after long‐term ethanol treatment and ethanol withdrawal

2000 
We have analysed the influence of long-term ethanol exposure on the effect exerted by Ca 2+ on the binding of tritiated inositol 1,4,5-trisphosphate to its receptors in rat cerebellar membranes. After 21 days of ethanol treatment the binding of the agonist was reduced in the absence of Ca 2+. The decrease was due to reduction in B max without any alteration of K d. In membranes from control animals Ca 2+ inhibited the binding of InsP 3 in a dose-dependent manner by altering the affinity of the protein for the ligand. However, the inhibitory effect of Ca 2+ was abolished following chronic ethanol exposure. Five days after withdrawing ethanol, the B max recovered to control values, but the inhibitory effect of Ca 2+ was recovered at only 10 days after withdrawal. The results indicate that long-term ethanol exposure may have differential effects on the InsP 3 binding site and on the Ca 2+ binding site, or alternatively on a Ca 2+ -related regulatory cycle.
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