Regulation of preglomerular microvascular 20-hydroxyeicosatetraenoic acid levels by salt depletion.

Background: 20-hydroxyeicosatetraenoic acid (20-HETE) is the preeminent renal eicosanoid. The protean properties of 20-HETE - vasoactivity, mitogenicity and modulation of transport in key nephron segments - serve as the basis for the essential roles of 20-HETE in the regulation of the renal circulation and electrolyte excretion and as a second messenger for endothelin-1 (ET-1) and a mediator of selective renal effects of angiotensin II (AII). Renal autoregulation and tubular glomerular feedback are mediated by 20-HETE through constriction of preglomerular microvessels, particularly afferent arterioles.
Methods and Results: We had reported that rat preglomerular microvessels (PGMV; afferent-interlobular-arcuate/interlobular) in response to angiotensin II (AII) generate primarily 20-HETE and lesser quantities of 19-HETE. We have now addressed a possible link between the renin-angiotensin-system (RAS) and induction of cyclooxygenase (COX-2). As Na+ deprivation induces COX-2 expression/activity in the renal cortex and AII stimulates release of 20-HETE from PGMV, we used a stimulus, low dietary salt, to activate the RAS and COX-2 and thereby explore potential interactions involving 20-HETE and COX-2.
Conclusions: The capacity of COX to metabolize 20-HETE to prostaglandin analogs e.g., 20-OH PGF2a and 20-OH PGE2, may be critical to modifying the renal vascular and tubular actions of the eicosanoids.