Meeting Abstract
During the reproductive season, anuran males display high plasma levels of androgens (A) and corticosterone (C), associated with testicular development and vocal behavior. Steroid hormones are immunomodulators, and elevated steroid plasma levels steroid plasma levels during reproduction might affect immunocompetence. Anuran males from the Brazilian semi-arid, the Caatinga, show higher A and C plasma levels and immunocompetence, especially when calling. These data suggest that higher steroid plasma levels, associated with expression and maintenance of calling activity, show immune-enhancing effects. However, the direct effects of A and C on immunocompetence remain to be tested in these species. We collected 39 males of R. jimi, during the reproductive season and sampled blood through cardiac puncture to measure basal hormone plasma levels and plasma bacterial killing ability (BKA). Afterwards, animals were placed individually in plastic boxes and randomly separated in 5 treatment groups: Placebo [5 uL of vehicle (sesame oil)] (P), testosterone (T) low dosage (12ug of T propionate) (Tlow), T high dosage (20 ug of T propionate) (Thig), C low dosage (7 ug of C) (Clow), and C high dosage (14 ug of C) (Chig). The treatment was conducted 24h after animals were collected from the field. We collected a blood sample 1 and 12h after the treatment to obtain plasma hormone levels and BKA. After hormonal treatment, we also subjected the animals to a phytohemaglutinin (PHA) challenge. As stablished in previous studies, their paws were measured 0, 12 and 24h after the PHA injection. Both treatments (low and high) successfully increased the plasma levels of their respective steroids, 1 hour after treatment (Tlow, Thig, Clow, Chig). The effects of hormone treatment on the immunological parameters are currently in analysis, and will be discussed in the presentation.
