Corpus cardiacum stimulated trehalose efflux from cockroach (<i>Periplaneta americana</i>) fat body: control by calcium

Abstract

Cockroach fat body incubated in a simple physiological saline solution releases trehalose to the surrounding medium. The output of trehalose occurs in the absence of ambient Ca 2+ and decreases slowly with time. In two separate experiments, 0.1 mM CaCl 2 added to the saline increased the output of trehalose on average by 70% but higher concentrations of Ca 2+ did not further increase the efflux of trehalose. Stimulation of trehalose efflux by corpus cardiacum extract is absolutely dependent on extracellular Ca 2+ , no increase occurring beyond the basal level in the absence of the ion. The activity of corpus cardiacum extract increases as the concentration of CaCl 2 is increased to 0.5 mM. This concentration of Ca 2+ in the saline permits the extract to increase trehalose efflux by as much as 60% above the basal level. Corpus cardiacum extract, as well as the hypertrehalocaemic agents cyclic AMP and theophylline, increase significantly the influx of Ca 2+ into fat body in vitro. The basal efflux of trehalose from fat body and that stimulated by corpus cardiacum extract is not dependent on extracellular Mg 2+ .