Prostaglandin E sub(2) in the salivary glands of the female tick, Amblyomma americanum (L.): calcium mobilization and exocytosis

• Published in: Insect biochemistry and molecular biology 1998-04, Vol.28 (4), p.221-228
• Main Authors: Qian, Ying, Yuan, Jing, Essenberg, R C, Bowman, A S, Shook, AL, Dillwith, J W, Sauer, J R
• Format: Article
• Language: English
• ISSN: 0965-1748

A cholera toxin-sensitive, prostaglandin E sub(2) (PGE sub(2)) specific receptor has been identified in the plasma membrane fraction of tick salivary glands. In the present study, we report that stimulation of dispersed salivary glands of the lone star tick Amblyomma americanum (L.) with 1 nM to 10 mu M PGE sub(2) increased the intracellular concentration of inositol trisphosphate (IP sub(3)) in a dose-dependent manner. Incubation of dispersed tissue with 1 nM to 10 mu M PGE sub(2) also stimulated release of super(45)Ca super(2+) from preloaded tissue. PGE sub(2) (10 mu M) did not stimulate an influx of super(45)Ca super(2+). Therefore, the PGE sub(2) receptor in the salivary glands appears to activate a phosphoinositide phospholipase C signalling pathway to increase formation of intracellular IP sub(3) and, thus, mobilize Ca super(2+) from intracellular stores. Incubation of dispersed salivary glands with 1 nM to 1 mu M PGE sub(2) stimulated secretion of anticoagulant protein, but not at < 1 nM or > 1 mu M PGE sub(2). In addition, the mammalian PGE sub(2) EP1 receptor antagonist AH-6809 affected secretion of anticoagulant by dispersed salivary gland tissue at a low concentration supporting the hypothesis that the PGE sub(2) receptor in tick salivary glands is EP1-like. We propose that a major function for PGE sub(2) in tick salivary glands is to mobilize Ca super(2+) and stimulate secretion (exocytosis) of bioactive proteins into the tick's saliva during feeding.