(953.23) The Influence of Ovariectomy on Performance and Thermoregulation During Exertional Heat Stroke in Mice

Poster Board Number: E571

Christian Garcia (Florida State University), Liliana Renteria (Florida State University), Gabriel Leite-Santos (Florida State University), Isela Valera (Florida State University), Jose Pindado (Florida State University), Corrinne Hickman (Florida State University), Jillian Carta (Florida State University), Jermaine Ward (USARIEM), Shauna Ward (USARIEM), Lisa Leon (USARIEM), Orlando Laitano (Florida State University)

Background: Exertional heat stroke (EHS) is a condition characterized by central nervous system dysfunction and multi-organ injury in hyperthermic victims. Most studies addressing EHS pathophysiology are performed in males. This is a concern since there is an increasing participation of females in sports, active military service, and sex-dependent susceptibilities to EHS. Preclinical data suggest that female mice outperform male mice regarding distance ran, speed, and time to collapse in a model of EHS. Importantly, differences in body mass between males and females do not explain these contrasting heat tolerances. Whether the female sex hormones could account for the superior performance in the heat remains unknown. Our goal was to determine the influence of female sex hormones on performance and thermoregulatory parameters in a preclinical model of EHS.

Methods: We performed ovariectomy (OVX, n=8) or sham (n=8) surgeries in young adult (18 weeks old) female C57/BL6 mice. Ovariectomy was performed by the bilateral removal of the ovaries. To allow for real time monitoring of core temperature during the entire experiment, all mice were implanted with telemetry emitters at the time of ovariectomy/sham surgeries. Upon recovery from surgeries and training (~6 weeks), all mice underwent the EHS protocol in an environmental chamber set at 37.5℃ and 40% relative humidity. Mice exercised on a running wheel until experiencing loss of consciousness.

Results: Ovariectomy increased body mass by 10% at the time of EHS (Sham = 25 ± 1 vs OVX = 28 ± 2 g, Plt;0.05), resulted in 35% shorter distance (Sham = 753 ± 189 vs. 490 ± 87 m, Plt;0.05), 25% shorter time to collapse (Sham = 126 ± 21 vs. OVX = 95 ± 12 min, Plt;0.05), and 15% lower final speed (Sham = 9 ± 1 vs. OVX = 7.5 ± 1 m/min, P lt; 0.05).

Conclusion: Ovariectomy negatively impacts tolerance to EHS. Ovariectomized mice not only displayed a marked decrease in performance during the EHS trial but also gained more mass than their controls. This suggests that female sex hormones are required for a greater tolerance against EHS.

Supported by DoD contract #W81XWH21C0073 to OL. lt;igt;The opinions or assertions contained herein are the private views of the author(s) and are not to be construed as official or reflecting the views of the Army or the Department of Defense.lt;/igt;