HEMODYNAMIC FACTORS IN ACUTE-RENAL-FAILURE (ARF)

Renal blood flow is not luxurious, it results from the metabolic demands of renal medulla and cortex. Within both areas, effective shuntdiffusion for blood gases is present. In the outer medulla, the oxygen supply of the thick ascending limb (TAL)-segments especially those of outer cortical nephrons is limited and tubular demands are regulated by the tubuloglomerular feedback. Thus inflowing tubular fluid into Henle's loop can be adapted to the oxygen supply of the TAL-segment and its proximal convoluted tubule (PCT). This adaption works oscillating, experimentally in the rat with a frequency of 30 mHz (2/min) and can be measured by oscillating of proximal tubular pressures, with a phase lag of distal sodium concentration and by oscillating oxygen pressures measured at the renal surface. A change between aerobe supply to glycolysis at the TAL-segment led via a changed fluid sodium concentration at the macula densa to an adjustment of oxygen consumption considering also the fact, that proximal tubules practically have no anaerobic metabolic reserves. If under ischemic and hypoxic conditions reduction of transport capacity is inadequate, deterioration of proximal tubuli and of TAL-segments may be programmed as the kidney's answer: acute renal failure (ARF).