| Energy metabolism and transport function of the kidney
|
| The kidney consumes large amounts of oxygen, mainly to support active sodium transport
|
| Figure 22.7 The structure of the nephron and of its major transport sites. |
Most of the metabolic processes in the kidneys are aerobic, and consequently oxygen consumption in the kidneys is high: it approximately equals that of the cardiac muscle, and is three times greater than that of the brain. Such high metabolic activity is required to maintain tubular reabsorption:
about 70% of the consumed oxygen is used to support active sodium transport, which in turn determines the reabsorption of glucose and amino acids. The partial pressure of oxygen (pO2) is greater in the kidney cortex than in the medulla; because of the relatively low pO2, and the concurrent high activity of Na+/K+-ATPase; therefore, the distal segments of the nephron are particularly vulnerable to a decreased oxygen supply.
|
| Main energy substrates in the renal cortex are fatty acids, lactate, glutamate, citrate, and ketone bodies. Renal tubular cells with a high Na+/K+-ATPase activity possess multiple mitochondria close to the plasma membrane, so that the ATP released to the cytosol is easily accessible.
|
|
