Abstract
The purpose of this study was to examine the effect of exogenous cyclic nucleotides and inhibitors of cyclic nucleotide phosphodiesterase on trehalose synthesis in Periplaneta americana. Both adenosine 3′,5′-monophosphate (cyclic AMP; free acid) and dibutyryl cyclic AMP (db cyclic AMP) were without effect on haemolymph trehalose levels in normal or neck-ligated cockroaches. Similarly, theophylline at a final concentration of approx. 6 mM had no effect on trehalose in neck-ligated cockroaches but caused a small increase in the non-ligated insect. In vitro, the efflux of trehalose from fat body was inhibited by caffeine, theophylline and aminophylline. The inhibitory effect of theophylline on trehalose efflux was potentiated by corpus cardiacum (CC) extract. In contrast to the inhibitory effect of caffeine, theophylline and aminophylline, isobutyl methylxanthine (IBMX) had a stimulatory effect on trehalose production which was dependent on extracellular Ca 2+. Subthreshold concentrations of IBMX and CC extract combined had a positive stimulatory effect on trehalose efflux. Neither cyclic AMP (free acid) nor db cyclic AMP stimulated trehalose efflux from fat body in vitro. Our studies suggest that activation of phosphorylase alone is unable to explain the stimulation of trehalose synthesis by CC hormones.
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