Effects of high altitude and exercise on plasma erythropoietin in equids

Abstract

To help resolve the mechanistic bases for haematological adaptations (, 28% increase in red blood cell volume) of equids to high altitude (3800 m, barometric pressure P b , 487 mm Hg) and exercise, plasma erythropoietin concentration ([EPO]) was measured at rest and following exercise in six, moderately fit equids (four Arabians, one Quarter Horse and one Shetland Pony; four females and two males; age 9.0^4.5 years (mean^SD)).[EPO] was measured on 2 days at 225 m (i.e. , sea level; P b , 743 mm Hg), over the course of a 10-day altitude exposure, and then again for 2 days after return to sea level. A standard track exercise test (submaximal, speed set-to-heart rate of 110 (trot), 150 (canter), 180 (gallop) bpm) was performed 2 days pre-high-altitude exposure and on three separate days at high altitude. In addition, a maximal incremental exercise test was performed on a high-speed motor-driven treadmill at sea level and 2 days following return to sea level from high altitude. Resting [EPO] increased from 28^29 at sea level to 144^46 mU ml 21 (P , 0.05) on the first day at high altitude. By day 2 at high altitude, [EPO] had returned to baseline (31^24 mU ml 21 , P . 0.05 vs. pre-high altitude) and did not change over the remaining 8 days at high altitude nor over the 2 days after return to sea level. [EPO] was not significantly altered by acute exercise at sea level or at 3800 m. These results indicate that [EPO] increases rapidly (though transiently) in response to hypobaric hypoxia but not to acute exercise, and that exercise does not appear to potentiate the altitude response. Thus, if any [EPO]-derived haematological adaptations to high altitude are present, these appear to result from a transient , 4-fold elevation of [EPO] rather than any sustained increase in this signalling mechanism, at least in the equid.

The different hormonal system during exercise stress coping in horses

“…Erythropoietin (EPO) is a peptide hormone produced by the kidneys in response to hypoxia sensed by receptors of the renal vasculature. Recently, it has been reported that acute exercise does not induce an increase of EPO in normal horses, neither in horses performing at altitude [81]. With pronounced effects of both central and peripheral control of cardiovascular function [82,83].…”

Efeito da idade e sexo sobre a concentração sérica de eritropoietina em equinos da raça Árabe

“…McKeever (2002) concluiu que os equinos possuem uma habilidade inata para tolerar alterações agudas induzidas pelo exercício e altitude. Posteriormente, McKeever et al (2010) observaram que a exposição dos equinos a altas altitudes aumentou a concentração de EPO em 387% no primeiro dia. No entanto, 12 h mais tarde no segundo dia a EPO retornou aos valores normais pré-altitude.…”

Evaluation of cobalt as a performance enhancing drug (PED) in racehorses

“…Horses have an exceptionally high capacity to utilise oxygen, and move their blood volume across the pulmonary circulation, a feature accompanied by a marked exercise induced arterial hypoxemia (Fenger et al, 2000). Additionally, horses store one third to one half of their red blood cell mass in their spleen, which likely contributes to their high aerobic capacity (McKeever et al, 2010b). Horses also fail to respond to a move to altitude with a sustained EPO response, such as is seen in other species (McKeever et al, 2010b).…”

“…Additionally, horses store one third to one half of their red blood cell mass in their spleen, which likely contributes to their high aerobic capacity (McKeever et al, 2010b). Horses also fail to respond to a move to altitude with a sustained EPO response, such as is seen in other species (McKeever et al, 2010b). We did not measure HIF in this study, but horses with heaves are able to respond to hypoxia with an increase in HIF (Toussaint et al, 2012), and equine dermal cells are able to respond to Co with an increase in HIF (Deschene et al, 2012), so it is likely that the lack of an EPO response to Co shown in other studies and confirmed here is related to an attenuated response of the horse to HIF rather than a lack of HIF response.…”