P1.31 Wednesday, Jan. 4 Steroid correlations in plasma, tissue and water samples CREIGHTON, A.E.*; SINKIEWICZ, D.M.; WILCZYNSKI, W.; Georgia State University; Georgia State University; Georgia State University firstname.lastname@example.org
The study of steroid hormones and their mode of action is ubiquitous in all vertebrate and invertebrate organisms. The predominating theories indicate that sex steroid hormones are made primarily in the gonad and are released into plasma where they are free to pass through the plasma membrane of target tissues, and thus, levels of steroids in the tissues should reflect levels found in plasma. We chose to test this assumption in the green tree frog (Hyla cinerea), an animal in which reproductive behavior is seasonal and highly dependent on circulating sex steroid levels. We also collected samples to examine a non-invasive approach for steroid collection. Six frogs (3 male and 3 female) were placed in individual water baths for 30 minutes and euthanized immediately. Following decapitation plasma samples and tissue (brain, gonad, and liver) were collected and flash-frozen. Tissue samples were homogenized and steroid hormones extracted via C18 columns (Waters) from all tissue, plasma, and water samples. Extractions were measured using enzyme immunoassay kits (Cayman) for testosterone (T), and corticosterone (CORT). We found a strong, significant correlation between plasma and brain CORT (r2=0.864, p=0.022) however; this was not seen with T (r2=0.283, p=0.356). In the water vs. plasma samples we found a significant correlation in T (r2=0.659, p=0.0497), which was not observed in CORT (r2=0.205, p=0.3667). The significance of these results was not affected by adjusting for body mass. This suggests that plasma measures are a strong predictor of brain measures with respect to CORT, and water sample measures are a strong predictor of plasma measures with respect to T.