Local anesthetics: stimulation of incorporation of inositol into phosphoinositides in guinea pig cerebral cortical synaptoneurosomes.
Various local anesthetics enhanced the incorporation of [3H]inositol into phosphoinositides in guinea pig cerebral cortical synaptoneurosomes. Dibucaine, QX-572 and dimethisoquin showed maximum stimulation at 100 microM, tetracaine and diphenhydramine at 300 microM, and QX-314 at 1 mM, while quinacrine, lidocaine and cocaine showed no or only slight stimulation. There was no correlation between local anesthetic activity, estimated by inhibition of the 22Na+ flux elicited by the sodium channel activator batrachotoxin, and the potency for stimulation of inositol incorporation. A quaternary, relatively weak, local anesthetic, QX-572, was the most potent agent in stimulation of inositol incorporation, while the next most potent agent was dibucaine, a tertiary, very potent, local anesthetic. Dibucaine did not affect the uptake of [3H]inositol by synaptoneurosomes. The incorporation of [3H]inositol into phosphoinositides was increased in calcium-free buffer. The presence of dibucaine resulted in further stimulation of [3H]inositol incorporation in calcium-free buffer. Although dibucaine and QX-572 markedly stimulated incorporation of [3H]inositol into phosphoinositides, only QX-572 significantly enhanced the incorporation of 32PO4(3-) into phosphoinositides. The results suggest that certain local anesthetics enhance a pathway involving an exchange reaction between inositol and the phosphoinositol ester bond of phosphatidylinositol, but do not markedly affect the de novo pathway of phosphoinositide synthesis.
Nishizawa
Y
Y
Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institute of Health, Bethesda, MD 20892.
Gusovsky
F
F
Daly
J W
JW
D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D007294:Inositol / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D000779:Anesthetics, Local; D010716:Phosphatidylinositols; D007294:Inositol