Meeting Abstract
Life history theory posits an intrinsic trade-off between survival and reproduction but the proximate mechanisms regulating these tradeoffs are not well understood. The glucocorticoid-driven stress response is thought to mediate this tradeoff. Corticosteroid-binding globulin (CBG) likely regulates corticosterone’s (CORT) access to tissue. CBG varies by species, season, population, life history sub-stage, sex and changes with acute and chronic stress. However, there is still disagreement as to both CBGs role in stress reactivity, as well as the best methods for measuring plasma CBG. Charcoal and vacuum filtration are the main techniques for measuring CBG. I focus on the vacuum filtration method and address the critique of temperature’s effect on the disassociation constant of CBG. I ran CBG assays at two different temperatures (21˚C and 41˚C) to understand the differences in estimates of the dissociation constant (Kd). Using house sparrow plasma, I demonstrate a temperature-sensitivity of the CBG assay and suggest that we are under-estimating the amount of free CORT across several species birds, and likely across vertebrates. An understanding of CBG is essential to studies involving stress and behavior.
