Sex differences in the erythropoietin response to hot tub treatment and carbon monoxide inhalation

The kidney increases erythropoietin (EPO) when oxygen delivery is reduced, and when reductions in oxygen delivery are sustained, increased EPO results in increased red blood cell (RBC) production. More recently, carbon monoxide (CO) and heat have been used chronically to increase RBC production and therefore hemoglobin (Hb) mass. However, studies examining the acute effects of these interventions are limited, and no studies have examined these interventions in women. The purpose of this study was to examine the effects of CO inhalation and heat treatment alone and in combination on circulating EPO and determine if there are sex differences in these responses. 11 healthy subjects completed the study (6 women). Baseline blood was drawn to measure iron, ferritin, and transferrin concentrations. Hb mass was measured via the 10-minute CO-rebreathe method. Subjects completed three interventions – CO inhalation (carboxyhemoglobin 13.01±2.5%) hot tub immersion (40 degrees C for 45 minutes), and combined CO and hot tub – in a randomized crossover design. Renal blood velocity (RBV) was measured via ultrasound during all interventions. Venous blood was drawn at baseline and every hour for 6 hours post-intervention for measurements of EPO. All interventions reduced renal oxygen delivery (Δ47.5±21mL O2/min), and there were no sex differences in the reduction in oxygen delivery. All three treatments similarly increased EPO from baseline to peak concentration (Δ4.94±5.6mIU/mL). Women had a significantly greater increase in EPO than men to all three interventions (Δwomen 8.22±5.6mIU/mL; Δmen 1±2.06mIU/mL). The degree of EPO increase on all three days negatively correlated with Hb mass (R2=0.64) and positively correlated with transferrin (R2=0.73). Women may respond better to these interventions aimed to increase EPO, but the degree of responsiveness may depend on baseline Hb mass as well as transferrin concentrations. Wu-Tsai Human Performance Alliance at Oregon This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.