17,18-epoxyeicosatetraenic acid (17,18-EEQ), the most abundant cytochrome P450 (CYP)-eicosanoid in C. elegans, is a potential signaling molecule in the regulation of pharyngeal pumping activity. Here we tested the hypothesis that stereo-discrimination of this chiral molecule may hint the existence of a receptor in the pharyngeal muscle and/or neuronal cells. We analyzed the effect of short-term incubation in both well fed and starved condition and found that the stereoisomer 17(R),18(S)-EEQ, clearly rescued impairments of pharyngeal pumping in D-6 fatty acid desaturase mutant strain
fat-3(
wa22). After treatment with the 17(S),18(R)-EEQ stereoisomer, however, we found no effect on pumping activity. In addition, we will analyze the total endogenous eicosanoid stereoisomer content of C. elegans by chiral LC/MS-MS to see whether or not only specific stereoisomers are endogenous resources. 17(R),18(S)-EEQ was more active in
ceeh-1(
ok3153) mutant background in comparison to other stains. We suspect that
ceeh-1(
ok3153), failing to produce a functional active soluble hydrolase (sEH), is unable to efficiently catalyze the hydrolysis of 17,18-EEQ to the corresponding diol (17,18-DHEQ), which we found correlated with a loss of function of this signaling molecule. 17,18-DHEQ treatment was inactive in a C. elegans' pumping assay.