Ecdysone 20-monooxygenase activity in land crabs

CYP330A1 and CYP4C39 enzymes in the shore crab Carcinus maenas: sequence and expression regulation by ecdysteroids and xenobiotics

Cytochrome P450 enzymes (CYP enzymes) catalyse important metabolic reactions of exogenous and endogenous substrates, including steroid hormones. Here, we report the first two CYP sequences from the shore crab, Carcinus maenas. Two complete cDNAs isolated from crab hepatopancreas encode CYP enzymes named CYP330A1, the first member of a new family, and CYP4C39. CYP330A1 is closest related to members of the CYP2 family (37.3% identical to mouse CYP2J6) and CYP4C39 is most identical to crayfish CYP4C15 (59.5%). CYP330A1 gene expression was induced in hepatopancreas of male green intermoult crabs by ecdysone and ponasterone A, but also by benzo(a)pyrene and phenobarbital. CYP330A1 induction was not observed in red crabs. The present results indicate that the CYP330A1 enzyme may be involved in ecdysteroid metabolism, presumably catabolism, and in the detoxification of environmental pollutants. Ecdysteroids or xenobiotics did not affect CYP4C39 gene expression. The fact that both ecdysteroids and xenobiotics affect CYP330A1 gene expression indicates that mutual interactions between chemical exposures and endocrine functions may exist in the shore crab.

Role of the midgut gland in metabolism and excretion of ecdysteroids by lobsters, Homarus americanus

The chromatographic profile of ecdysteroids (Ecds) from the midgut gland (MG) of juvenile female lobsters, Homarus americanus, was examined using high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA) over four stages of the molt cycle. Upon initial examination, highly polar Ecd conjugates appeared to be the principal metabolites found in all molt stages. HPLC fractions containing apolar Ecds initially exhibited low RIA activity. Upon hydrolysis with a Helix pomatia enzyme preparation and reanalysis, significant amounts of other Ecds were released. Amounts of apolar Ecd conjugates were estimated, at their highest levels, to be at least 50% of the total Ecds in MGs of molt stage D3 lobsters. Only the MG formed significant amounts of apolar Ecds upon in vitro culture with [3H]ecdysone ([3H]E). Epidermis and antennal gland significantly increased their rates of [3H]E metabolism in vitro between molt stages C4 and D1. This result further supports the idea that regulation of ecdysteroid metabolism, at least in selected tissues, may be important in the molt cycle regulation of hormone titers. Using gel filtration column chromatography and sucrose density gradient centrifugation analyses, evidence was found for association of apolar Ecds with a protein(s) from MG cytosol. The protein was estimated to have a molecular weight of 180,000-200,000 and specifically bound apolar Ecds.

Ecdysteroids in relation to the molt cycle of the American lobster, Homarus americanus. I. Hemolymph titers and metabolites

Hemolymph ecdysteroid (Ecd) titers were measured using radioimmunoassay (RIA) during the molt cycle of the American lobster, Homarus americanus. Individual animals showed small, transitory rises of Ecds which increased in magnitude with the onset of premolt and culminated in a large premolt peak at morphological stages D2(2)-D3(1). Male lobsters had significant postmolt peaks and late premolt titers that remained high until ecdysis. In females, postmolt peaks were absent and late premolt titers reached basal levels before ecdysis. At least seven different Ecd metabolites were identified by high-performance liquid chromatography-RIA analyses. High polarity products (HP) were the most abundant metabolites in virtually every molt stage. Titers of HP were significantly higher in males during late postmolt-early intermolt and in late premolt. Levels of 20-hydroxyecdysone (20E) were equivalent in both sexes and correlated with the morphological changes associated with premolt. Evidence was also obtained for the presence of ecdysone, ponasterone A, and other as yet unidentified metabolites. The pattern of Ecd metabolites in the hemolymph supports other data indicative of 20E as the major molting hormone. Metabolism of 20E is primarily toward more polar compounds, including conjugates.