DOWN-REGULATION OF PHEROMONE BIOSYNTHESIS - CELLULAR MECHANISMS OF PHEROMONOSTATIC RESPONSES

The biochemical second messenger system during pheromonotropic and phe romonostatic activities was assessed and compared, The involvement of G-proteins was implicated by the stimulatory action of sodium fluoride (NaF), at a range of 1-2 mM, on both pheromone biosynthesis and intra cellular cAMP levels in isolated intersegmental membranes of Helicover pa armigera, However, cholera toxin did not mimic the pheromonotropic response of PBAN, The stimulatory action of NaF was significantly inhi bited by adrenergic agonists (tyramine and clonidine) as was observed at low levels of PBAN, At high levels of PBAN, although cAMP productio n was inhibited, pheromone biosynthesis was unaffected by clonidine, A similar phenomenon was observed with the ionophore, thapsigargin, in which adrenergic agonists did not inhibit pheromone biosynthesis but r educed intracellular cAMP to basal levels, Thus pheromonotropic activi ty exhibited both cAMP-independent and cAMP-dependent stimulatory resp onses, The calcium calmodulin inhibitor, W7, inhibited pheromone biosy nthesis and intracellular cAMP production which was induced either by Hez-PBAN, NaF or thapsigargin, The pheromonostatic activity by clonidi ne was prevented in the presence of pertussis toxin, thereby indicatin g the involvement of inhibitory G-protein (Gi) in the inhibitory actio n of adrenergic agonists on the activity of Hez-PBAN. From the results we hypothesized that negative regulation of pheromonotropic activity occurs at the membrane receptor level by the interaction of an adrener gic receptor. Copyright (C) 1996 Elsevier Science Ltd