Juvenile hormone metabolism, binding and esterase activities in the haemolymph of the adult monarch butterfly (Danaus p. plexippus L.: Lepidoptera)

Abstract

The interaction of [3H]juvenile hormone I (JHI) with haemolymph of the adult monarch butterfly, Danaus p. plexippus L. was investigated. Whole haemolymph bound [3H]JHI preferentially in vitro compared to bovine serum albumin or buffer alone using a charcoal binding assay. [3H]JHI was converted to polar metabolites by adult haemolymph as assessed by an octane: methanol-H2O partition assay and thin layer chromatography. Phenyl methyl sulphonyl fluoride (PMSF), a potent esterase inhibitor, was effective in decreasing the conversion of [3H]JHI to polar metabolites, thus suggesting the presence of JH esterase (JHE) activity. Post eclosion JHE activity assessed in vitro increased in females, peaking at day 6 post eclosion; while in males there was an initial decrease followed by a small peak at day 6. The fluctuations observed were not attributable to haemolymph volume changes. [3H]JHI metabolism assessed in vivo at 40, 140, 240 and 1380 min post injection, tested at four different stages or periods of the life cycle, indicated that the greatest metabolism of [3H]JHI occurred at day 3 post eclosion in both sexes followed respectively by January males and females, June-July males and females, September females and finally September male wild caught adults. JH binding assays carried out on haemolymph fractions separated by Sephadex G-100 column chromatography indicated a peak of JH binding activity corresponding to 29,500 ± 6000 mol. wt (x ± SEM, n = 6). Bioassay indicated that the bulk of endogenous JH was associated with this peak of JH binding activity. JHE activity assessed in these same fractions indicated two major peaks one > 100,000 mol. wt and the other at 79,000 ± 5000 mol. wt (x ± SEM, n = 6). The fractions of the smaller mol. wt peaks were found to inactivate both [3H]JHI and endogenous JH biological activity when assessed using the Galleria wax test. © 1984.

Publication Title

Insect Biochemistry

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