Mechanism of ischemia
From the time a patient is identified as a potential organ
donor it is critical to maintain adequate organ perfusion
and avoid hypoxemia. Maintenance of intracellular oxygen
content is dependent on hemoglobin delivery to the renal
microvascular space. Ischemic kidney injury occurs after
failure of a cadre of physiologic responses, including
arteriolar vasoconstriction, xanthine dehydrogenase activation
(XD) and heme oxygenase-1 (HO-1) (Figure 1). In
times of decreased perfusion, the kidney’s afferent arteriole
acts as a baro-detector distinct from the sympathetic
nervous system (16). Decreased vascular wall tension activates
renin synthesis in the macula densa. The concentration
of ligands that bind to transmembrane G protein
coupled receptors (GPCR), including thromboxane A2, angiotensin
II and endothelin-1 increases tomaintain intravascular
perfusion pressure (17,18). Calcium is released from
the sarcoplasmic reticulum, promoting actin myosin coupling.
In a hypothermic state, renal tubular cells avoid intracellular
Ca2+ accumulation due to their low membrane
permeability (19,20).
As aerobicmetabolism is turned off, volatile iron-containing