Fuel Oil–induced Adrenal Hypertrophy in Ranch Mink (Mustela Vison): Effects of Sex, Fuel Oil Weathering, and Response to Adrenocorticotropic Hormone

Abstract

ABSTRACT:Environmental contamination by petroleum hydrocarbons from anthropogenic sources can be a cause of stress for free-ranging wildlife. The response of wildlife to chemical contaminants requires that the hypothalamic-pituitary-adrenal (HPA) axis be precisely regulated to allow for proper glucocorticoid-mediated adaptive responses. Chronic oral exposure to low concentrations of bunker C fuel oil causes the development of adrenal hypertrophy in male ranch mink (Mustela vison) without increasing serum or fecal glucocorticoid concentrations. This hypertrophy is an adaptive response to fuel oil-induced adrenal insufficiency. To determine if the same phenomenon occurs in female mink or male mink exposed to artificially weathered fuel oil, female mink were fed 0 ppm (mineral oil) or 420 ppm fuel oil and male mink were exposed to 0 ppm, 420 ppm fuel oil, or 480 ppm artificially weathered fuel oil in the diet for 60-62 days. At the end of the exposure, serum glucocorticoid concentrations were assayed along with body and organ weight measurements. Fecal glucocorticoid concentrations were assayed at time points throughout the exposure. Male mink fed fuel oil or weathered fuel oil and female mink fed fuel oil had adrenal enlargement without any significant increases in the serum or fecal concentration of glucocorticoids, which is consistent with fuel oil-induced adrenal insufficiency. To address the physiological consequences of adrenal insufficiency, fuel oil-exposed male mink were administered an adrenocorticotropic hormone (ACTH) stimulation test. Fuel oil-exposed animals had a smaller incremental increase in serum glucocorticoid concentration after ACTH challenge compared to control animals. Our findings provide further evidence that the HPA axis of fuel oilexposed animals is compromised and, therefore, not able to respond appropriately to the diverse stressors found in the environment.

Adrenal Gland and Lung Lesions in Gulf of Mexico Common Bottlenose Dolphins (Tursiops truncatus) Found Dead following the Deepwater Horizon Oil Spill

“…Several studies have shown that PAHs or oil can affect the HPA axis and adrenal gland function. Hypoadrenocorticism has been reported in mink fed either bunker C or artificially weathered fuel oil [ 44 , 45 ]. In these mink, adrenal cortical hypertrophy with vacuolation of corticocytes was detected histologically.…”

Toxicological estimation of mortality of oceanic sea turtles oiled during the Deepwater Horizon oil spill

“…However, those chronic oral exposures to low concen trations of Bunker C oil did not alter serum or fecal glucocorticoid concentrations. In a second related study, mink were fed artificially weathered fuel oil in their diet for 60 to 62 d, and adrenal hypertrophy was also found at all doses and in both sexes (Mohr et al 2010).…”

“…and mink (e.g. Mohr et al 2008Mohr et al , 2010, as discussed in this section. We compared the estimated exposure in sea turtles to the levels and effects reported in 2 oil dose−response studies in mink (Mohr et al 2008(Mohr et al , 2010.…”

“…In the second study, mink were fed artificially weathered Bunker C fuel oil or mineral oil controls. For Bunker C fuel oil, male mink were fed 0, 420 or 480 ppm and female mink were fed 0 and 420 ppm fuel oil in their diet for 60 to 62 d (Mohr et al 2010).…”

“…, that specifically impacts the HPA axis (Mohr et al 2008(Mohr et al , 2010 for all exposure scenarios. However, it should be noted that the mink experiments were conducted with Bunker C fuel oil and not the DWH MC252 oil.…”