IN-VIVO AND IN-VITRO TISSUE-SPECIFIC METABOLISM OF JUVENILE-HORMONE DURING THE LAST STADIUM OF THE CABBAGE-LOOPER, TRICHOPLUSIA NI

In vitro metabolism of racemic JH III (5 mu M) was measured in fat bod y, midgut and integument homogenate during the last stadium of the cab bage looper, Trichoplusia ni. The JH esterase activity per mg protein peaked in these tissues in prewandering larvae on day 2 and was elevat ed in the fat body only in prepupae (on day 4). The JH epoxide hydrola se activity peaked on day 2 in midgut and on day 3 (in wandering larva e) in fat body and integument. No differences were noted in the overal l JH III metabolism in vitro per insect between wandering (day 3) larv ae and prepupae (day 4) and in the in vivo metabolism of 10R,11S-JH II when injected in oil and buffer or when topically applied at physiolo gical concentrations into these same stages, Regardless of the method of introduction of JH II, JH diol was produced in both wandering larva e and prepupae. JH acid and JH acid, diol were also produced but the p redominant product was a water soluble metabolite. The preferred subst rate for JH epoxide hydrolase at physiological concentrations was JH I I as opposed to JH II acid. Approximately half of the JH II after inje ction into wandering larvae was associated with the alimentary canal a nd carcass. The metabolites of JH II were evenly distributed. The impo rtance of JH epoxide hydrolase in JH metabolism in last stadium Lepido ptera is discussed.