Endogenous xanthurenic acid as a regulator of the crustacean molt cycle
By means of in vitro assay, it has been demonstrated that xanthurenic acid, a metabolite of 3-hydroxy-L-kynurenine which is contained in crustacean eyestalks (X-organ), acts as an inhibitor of ecdysteroidogenesis in Y-organs. Xanthurenic acid directly prevents an oxygenase (probably cytochrome P-450 mediated) from acting on ecdysone precursor(s). Injection with physiological doses of 3-hydroxy-L-kynurenine in saline delayed the onset of induced molts and prolonged the duration of molt cycles of eyestalk-ablated crayfish. Thus, the long-postulated molt inhibitory action of the eyestalk can at least in part be ascribed to xanthurenic acid or its precursor 3-hydroxy-L-kynurenine.