Increased Expression of a Constrictor Mechanism Mediated by 20-Hydroxyeicosatetraenoic Acid in Renal Interlobular Arteries of Rats Fed a K Deficient Diet.
Renal preglomerular vessels metabolize arachidonic acid (AA) to 20-hydroxyeicosatetraenoic acid (20-HETE), an eicosanoid that amplifies vasoconstrictor responsiveness. This study examines (a) the effect of variations in dietary K intake on renal 20-HETE synthesis, and (b) the significance of 20-HETE synthesis in relation to the regulation of renal interlobular artery (ILA) internal diameter (ID) in rats fed a diet with a low (0.004 mmol/g) or high (1.351 mmol/g) K content (LK and HK rats) for 10-12 days. Metabolism of 14AA to 20-HETE by renal microsomes from LK rats exceeded values by renal microsomes from HK rats (800±140 versus 263±29pmol/mg/min); P<0.05). Complementary studies were conducted on ILA mounted on a pressure-myograph and superfused with Krebs buffer. In ILA from LK rats, the ID after equilibration at an intraluminal pressure (IP) of 100 mmHg was 58±10 μm and increased (P<0.05) to 81±8μm after inclusion of the 20-HETE synthesis inhibitor DDMS (30 μM) into the buffer. In ILA from HK rats, the ID at 100mmHg was 77±3 μm and increased (P<0.05) to 87±4μm after DDMS treatment. The DDMS-induced increase of ID in ILA of LK rats (23±3 μm) exceeded (P<0.05) that in ILA of HK rats (10±3 μm). We also evaluated IP-ID relationships. Stepwise increases in IP within the range 40-100 mmHg elicited a myogenic response that decreased ID (expressed as % of passive ID). IP-induced decreases of ID in LK rats surpassed (P<0.05) those in HK rats. However, after treatment with DDMS myogenic constrictor responses were comparable in ILA from LK and HK rats. These data suggest that renal 20-HETE synthesis increases as dietary K decreases and that a constrictor mechanism involving 20-HETE is more prominently expressed in ILA of LK than of HK rats.