Meeting Abstract
Hormone levels are not necessarily uniform throughout the circulatory system, and thus estimates of circulating hormone concentrations may vary depending on the location or type of blood vessels from which samples are collected. Such variation may be of critical importance, both for understanding the dynamics of hormone action across tissues, and for appropriately designing experiments. We investigated whether levels of corticosterone (CORT) differed in blood samples collected from zebra finches (Taeniopygia guttata) using two common methods: wing venipuncture and trunk blood collection following decapitation. CORT changes rapidly and substantially during periods of stress; thus, we subjected finches to 60 min of restraint to elevate CORT. We collected blood from a wing vein after 60 min of restraint, and then two minutes later euthanized birds and collected trunk blood. Plasma CORT was lower in blood from trunk vessels than in blood from the wing vein (P = 0.01), an effect that was driven by males. Because the nature of trunk blood collection prevented alternating sampling order, we used a second group of finches to control for the possibility that this difference in CORT could have been caused by the order in which samples were collected. In this group we collected blood from a wing vein after 60 min of restraint and again two min later. Plasma CORT did not differ between these two successive wing bleeds (p=0.90), and was not related to the time between blood samples (p=0.783). In sum, CORT concentration differed depending on the source of the blood collected, suggesting that sampling methodology should be considered carefully when designing experiments and when drawing comparisons across studies.
