TITLE

EFFECTS OF CYCLIC GMP ON ECDYSONE 20-MONOOXYGENASE ACTIVITY

AUTHOR(S)

Drummond, Christopher A.; Smith, Stan L.

PUB. DATE

March 2008

SOURCE

Ohio Journal of Science;Mar2008, Vol. 108 Issue 1, pA-15

SOURCE TYPE

Academic Journal

DOC. TYPE

Article

ABSTRACT

Ecdysone 20-monooxygenase (E-20-M} is the cytochrome P-450 dependent steroid hydroxylase responsible for the conversion of the insect molting hormone ecdysone (E) to its more physiologically active form 20-hydroxyecdysone (20-HE). E-20-M activity fluctuates in a stage and tissue specific fashion. In the tobacco hornworm, Manduca sexta, midgut E-20-M undergoes a 50-fold increase in activity temporally coincident with larval-pupal reprogramming in the last larval stadium. This increase is elicited by its substrate E. In the present study, we found that the second messenger cyclic GMP may also be involved in the increase in midgut E-20-M activity (enzyme activity measured by radioassay). Pre-incubating midgut tissues with dibutyryl cyclic GMP elicited a 74% increase (586 pg 20-HE formed/min/mg tissue, n = 9) in E-20-M activity compared to untreated or dibutyryl cyclic AMP treated tissues (337 pg 20-HE formed/min/mg tissue, n = 9). Under in vivo conditions, injections of the guanylate cyclase inhibitors LY-83583 or methylene blue elicited decreases in E-20-M activity by 65% and 80%, respectively, compared to sham injected controls (control E-20-M activity 419 pg 20-HE formed/min/mg tissue, n = 19). Such inhibitions could be reversed with co-injections of dibutyryl cyclic GMP or SNAP, a guanylate cyclase activator. In addition, co-injecting dibutyryl cyclic GMP with suboptimal doses of the E agonist RH-5849 elicited higher midgut E-20-M activity (3-4X) compared to injections of E agonist alone. Collectively, these findings provide strong pharmacological evidence that the second messenger cyclic GMP may be involved in a steroid hormone regulated event.

ACCESSION #

31745956

Tags: CYCLIC guanylic acid;  ECDYSONE;  MONOOXYGENASES;  TOBACCO hornworm;  FISHES -- Genetics;  ADENYLIC acid

 

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