0732 Aquaporin studies relevant to the neonate

Previous summaries have drawn attention to the exciting discovery of aquaporins and abnormalities associated with conditions ranging from nephrogenic diabetes insipidus to cerebral oedema. Recent research has focused on conditions affecting the neonate, and in this regard it has been found that the well-described diuretic phase that follows the first few days of water retention and oedema in many preterm infants correlates with aquaporin-2 (AQP2) levels. Neonates showed a weight loss on ~day 3 associated with a >3-fold increase in urine output but without any change in fluid intake. Creatinine clearance also increased, indicating an increase in glomerular filtration rate. There was also a simultaneous increase in AQP2 excretion, suggesting that aquaporin-2 can contribute to urinary concentrating ability in early life. Another common problem in neonatology is that of cerebral oedema associated with hypoxic ischaemic encephalopathy (HIE). In this regard the well-described, abundant expression of AQP4 in astrocytes has been further studied, with the evidence suggesting that experimental AQP4 “knockdown” and inhibition may protect against water influx and astrocyte swelling during HIE, BUT may also delay water clearance in the resolution of astrocyte swelling during reoxygenation. These different roles of AQP4 and the likely future ability to modify the expression of aquaporins may yield novel therapeutic strategies for the prevention and treatment of HIE. Not quite neonatal but potentially relevant to the infant, and certainly topical as Chinese-made toys are being recalled because of problems with lead paint used in their manufacture, is the finding that brain oedema in lead poisoning is probably also mediated via lead’s interference with aquaporin and water transport across astrocyte membranes.

Read more:
Glia 2007; 55: 935-41
Neuroscience 2005; 136: 105-14
Nephron Physiol 2006; 104; 121-5