Chitinase activity in the epidermis of the fiddler crab, Uca pugilator, as an in vivo screen for molt-interfering xenobiotics.
We describe an in vivo screening assay that uses epidermal chitinase activity as the endpoint following a 7-day exposure of Uca pugilator to test chemicals. Chitinase, a chitinolytic enzyme, is the end product of endocrine cascades of a multi-hormonal system for control of crustacean molting. Wherever a molt-interfering agent adversely impacts the Y-organ-ecdysteroid receptor axis, the effect should be manifested by the activity of chitinase in the epidermis. Therefore, epidermal chitinase activity is an ideal endpoint for molt-interfering effects of xenobiotics. The validity of epidermal chitinase activity being used for such a purpose is supported by our finding that two injections of 20-hydroxyecdysone at 25 microg/g live weight induced a twofold increase in chitinase activity in the epidermis of U. pugilator. A total of nine chemicals were screened for molting hormone and anti-molting activities. o,p'-DDT was found to significantly inhibit epidermal chitinase activity while kepone and methoxychlor exhibited a tendency of inhibition of enzymatic activity. None of the remaining six chemicals, namely, p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), atrazine, tributyltin (TBT), methoprene, dieldrin and permethrin, had an effect on epidermal chitinase activity.
Zou
Enmin
E
Department of Biological Sciences, Nicholls State University, Thibodaux, LA 70310, USA. em.zou@nicholls.edu
Bonvillain
Ryan
R
D000818:Animals; D001681:Biological Assay; D003386:Brachyura / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D002688:Chitinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004441:Ecdysterone / Q000494:pharmacology; D004785:Environmental Pollutants / Q000633:toxicity*; D004817:Epidermis / Q000201:enzymology; D005260:Female; D007306:Insecticides / Q000633:toxicity*; D018978:Molting / Q000187:drug effects*; D015262:Xenobiotics / Q000633:toxicity*
D004785:Environmental Pollutants; D007306:Insecticides; D015262:Xenobiotics; D004441:Ecdysterone; D002688:Chitinases