CYCLIC-AMP CAN PROMOTE THE SECRETION OF DIGESTIVE ENZYMES IN STOMOXYS-CALCITRANS

Opaque zones from Stomoxys calcitrans midgut were maintained in vitro in a high potassium incubation medium for periods up to 30 min without significant release of trypsin-like digestive enzymes compared to stimulated opaque zones. Forskolin stimulated digestive enzyme secretion from this preparation in a time and dose dependent manner with maximal stimulation at and above 4 muM. Comparable results were obtained with dibutyryl cAMP where maximal stimulation occurred at 500 muM. Dibutyryl cGMP did not stimulate secretion. The results suggest cyclic AMP but not cGMP plays a role in the regulation of digestive enzyme secretion in S. calcitrans. The secretory response was dependent on pH (max. 6.6), temperature (max. 25-degrees-C) and oxygenation of the incubatory media. The results suggest that this preparation can be used to investigate the extracellular mechanisms controlling digestive enzyme secretion in S. calcitrans.