Renal Hemodynamic Response to Oral Protein Loading during Prolonged Mild Hypohydration

Session: (In-Person) Poster Presentation

Hypohydration, a state of low body water, can occur due to inadequate fluid consumption or with sweating during heat stress. The kidneys regulate body water through multiple mechanisms including modulation of renal blood flow. It is not known if prolonged hypohydration alters the control of renal blood flow. Renal blood flow control can be probed using an oral protein load, a stimulus that increases renal blood flow within 1-3 hours. We tested the hypothesis that prolonged mild hypohydration attenuates oral protein loading-induced increases in renal blood flow compared to a hydrated state (i.e., euhydrated). Eight healthy adults (5 females) arrived at the lab after 24 hours of fluid deprivation (HYPO) or when euhydrated (EUHY). Subjects ingested a whey protein beverage to stimulate increases in renal blood flow. Doppler ultrasonography was used to estimate renal blood flow from blood velocity in the renal and segmental arteries. Data were summarized as the peak increase in renal blood velocity. A mild hypohydration was confirmed by greater reductions in body mass in HYPO vs. EUHY (HYPO: -2.2±0.5%; EUHY: -0.3±0.7%, P=0.001). There were no differences between conditions in the peak increase in renal (HYPO: +5.6±3.8 cm/s; EUHY: +4.8±3.3 cm/s, P=0.54) and segmental (HYPO: +4.4±4.7 cm/s; EUHY: +3.4±4.0 cm/s, P=0.43) artery blood velocities. These findings indicate that prolonged mild hypohydration does not alter the kidneys’ ability to increase renal blood flow.