Structural and functional aspects of salivary fluid section in Calliphora.

Calliphora salivary glands are described, emphasizing correlations between structure and physiology. In vitro studies show that the distal part of each gland produces a potassium-rich primary saliva when stimulated with 5-hydroxytryptamine or cyclic AMP. The secretory cells have elaborate canaliculi opening into the lumen. Stimulation of the secretory region causes a 60-fold increase in fluid secretion rate without affecting cell structure. The proximal part of the gland reabsorbs potassium when stimulated with cyclic AMP, but 5-HT has no effect. Potassium reabsorption from the primary saliva results in formation of a dilute saliva. The structure of the secretory and reabsorptive cells is discussed with regard to the functional role of long narrow channels in transport.