The effects of 20-hydroxyecdysone and juvenile hormone III on tick cells

Two cell lines isolated from Rhipicephalus appendiculatus ( RAE 25) and Anocentor (= Dermacentor) nitens (ANE 58) responded to the invertebrate hormones 20-hydroxyecdysone (20-HE) and juvenile hormone III (JH III) in vitro. In the presence of 0.2 or 2 nMolar 20-HE, the cells of the continuous line RAE 25 attached to the culture substrate at a rate of 9% per hr for the first 8 hr, as did cells in growth medium. Twenty or 200 nMolar of 20-HE reduced the rate of cell attachment to 6% per hr, and in the higher hormone concentration the cells ceased to attach after 4 hr. Low concentrations (0.2 and 2 nMolar ) of 20-HE stimulated the growth of the RAE 25 line (P less than 0.02), but 200 nMolar or more inhibited growth (P less than 0.001). Twenty-HE suppressed the growth of the young line ANE 58 in a dose-dependent manner, but the decrease in cell growth was less pronounced than in RAE 25. Ten to 100 times more (2 and 20 mu Molar) 20-HE was needed to achieve significant growth suppression (P less than 0.025 and less than 0.005). The growth of both lines declined (P less than 0.01) by 20% ( RAE 25) or 30% (ANE 58) when the medium contained 38 mu Molar of JH III. The bimodal growth response of line RAE 25 to 20-HE also occurred in the presence of 3.8 and 38 mu Molar JH III, and 2 nMolar 20-HE counteracted the suppressive effect of 38 mu Molar JH III.(ABSTRACT TRUNCATED AT 250 WORDS)