Further investigations on the action of ecdysteroids on the salivary glands of the female tick Amblyomma americanum.

Two phytecdysteroids (abutasterone, makisterone A) and five synthetic ecdysteroid analogues, all at 1 microgram/ml, were tested on salivary glands from the female tick, Amblyomma americanum L. (Acari:Ixodidae), held in organ culture for four days. All of these substances caused a significant reduction in fluid secretory competence of salivary glands in vitro. This constitutes further evidence that the structural requirements for causing salivary-gland degeneration in ticks are similar to those generally required for ecdysteroid activity in other arthropods. Although vertebrate steroids are known to augment fluid secretory competence by salivary glands in organ culture, beta-estradiol was not able to attenuate the degenerating effect of 20-hydroxyecdysone, supporting the suggestion that ecdysteroids and vertebrate steroids have distinct sites/mechanisms of action on this tissue.