Lectures L 7 . 1 Why is main oxygen sensor located in the kidney ?

It is well establish that is direct relationship between oxygen uptake and sodium transport in the kidney. More than 60% of glomerular filtrate with its sodium content is reabsorbed in the proximal tubular cells, and half of that is transported due to Na, K-ATPase activity localized in antiluminal membranes of the cells. Oxidative metabolism is the major source of energy for proximal tubular cells of the cortex and oxidative phosphorylation is one and only source of ATP where mitochondrial density is particularly high at the antyluminal membrane of the cells. Therefore mitochondrial respiration creates a region with a very high oxygen consumption rate, and could result in oxygen diffusion gradients in the region where erythropoietin (EPO) is made in fibroblast cells. The balance of oxygen consumption for sodium reabsorbtion and oxygen delivery is reflected by the tissue oxygen pressure. This balance determines red blood cells mass adjusted to plasma volume. It is suggested that the kidney possesses unique ability to sense extracellular fluid volume through tissue oxygen signal. The role of the rennin-angiothensin system, hypoxia-inducible transcription factors and proline oxygenase –oxygen sensor-in modulating EPO will be discussed.