ISSN:
0739-4462
Keywords:
ecdysteroids
;
fatty acyl esters
;
ticks
;
Ixodidae
;
Boophilus microplus
;
h.p.l.c.
;
Chemistry
;
Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
The free ecdysteroid titre determined by radioimmunoassay in adult female Boophilus microplus showed a peak just prior to full engorgement and detachment of the ticks and decreased subsequently to a very low value. In contrast, the titre of polar ecdysteroid conjugates was very low. Ecdysone was the major ecdysteroid at peak titre and was accompanied by much lower levels of 20-hydroxyecdysone. In newly detached ticks, injected [3H]ecdysone was metabolized primarily (80%) into much less polar compounds, which could be resolved into at least three groups by reversed-phase h.p.l.c. These [3H] “apolar” metabolites were transferred to the newly laid eggs, where they accounted for the vast preponderance of ecdysteroids, the level of free hormone being low. Hydrolysis of the three groups of compounds with an esterase preparation from porcine liver yielding [3H]ecdysone, together with the release of [3H] ecdysteroid and fatty acids upon alkaline saponification of the compounds, suggests that they are of a fatty acyl ester nature. The chemical transformation of these “esters” into the corresponding acetonide derivatives indicates that the 2- and 3-hydroxyls of ecdysone remain unsubstituted in these compounds. Several tick tissues, including Malpighian tubules, ovaries, gut, and fat body, metabolized [3H]ecdysone in vitro forming the “apolar esters” as major products. The maternal ecdysteroid “esters” may function as storage forms of hormone (presumably hormonally inactive), which could be hydrolysed enzymically during embryogenesis releasing free ecdysteroids. Such enzymic hydrolysis of [3H]ecdysone “esters” by homogenates from developing eggs of B. microplus has been demonstrated.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/arch.940020105
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