Erythropoietin as a volume-regulating hormone: an integrated view.
The intravascular volume consists of 40% to 45% red cells. Their production is controlled predominantly by erythropoietin (EPO), a hormone that is secreted particularly when tissue hypoxia is present. Because of this high percentage of the total intravascular volume the question comes to mind that, in addition to hypoxia, can volume-regulation mechanisms, known to be responsible for the maintenance of plasma volume, modulate EPO secretion when the total vascular volume changes? Indeed, there is evidence that in situations in which the intravascular volume or specifically the intrathoracic volume is altered, EPO secretion is affected. EPO secretion increases when the intrathoracic volume decreases 24 hours after water immersion or after endurance exercise when a negative water balance prevails. A head-down tilt on the other side induces central engorgement leading to a decrease of EPO concentrations. Under these experimental conditions no hypoxia was seen, supporting the idea that a volume stimulus outgoing from intrathoracic parts of the circulation modulated EPO secretion. Further observations from the clinical side are needed to support these ideas and the consequences need to be implemented into clinical practice.
Kirsch
Karl A
KA
Department of Physiology, Charité-Universitätsmedizin and Center of Space Medicine, Berlin, Germany. ZWMB@charite.de
Schlemmer
Matthias
M
De Santo
Natale G
NG
Cirillo
Massimo
M
Perna
Alessandra
A
Gunga
Hanns-Christian
HC
D001775:Blood Circulation / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology*; D004921:Erythropoietin / Q000096:biosynthesis* / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D045265:Natriuretic Peptides / Q000378:metabolism; D012680:Sensitivity and Specificity; D014667:Vasopressins / Q000096:biosynthesis*
D045265:Natriuretic Peptides; D014667:Vasopressins; D004921:Erythropoietin