Hormonal Activation of Phosphoinositide Breakdown in the Presence of Guanine Nucleotides Using a Cell-Free System from Blowfly Salivary Glands

This chapter reviews the use of blowfly salivary glands as a model system for the investigation of hormone-stimulated phosphoinositide breakdown. There are several species of blowflies. Flies are maintained on water plus lean beefsteak and sucrose cubes obtained commercially in grocery stores. Mature flies lay their eggs on meat. Beefsteak, pig hearts, or rat liver is useful for this purpose. The paired salivary glands of the blowfly are thin tubes consisting almost exclusively of secretory cells with extensive canaliculi. The flies are killed and then immobilized by the use of pins or the wings and legs are removed and the abdomen opened. The glands do not appear to have any nerves and receive all nutrients and hormonal signals through the surrounding hemolymph. The two tubes come together in the anterior region of the thorax to form a common salivary duct. The chapter discusses the activation of phosphoinositide breakdown in cell-free systems using membranes from glands labeled by incubation with [³H]inositol.