Renal myogenic constriction protects the kidney from age-related hypertensive renal damage in the Fawn-Hooded rat

Introduction:Intact myogenic constriction plays a role in renal blood flow autoregulation and protection against pressure-related (renal) injury. However, to what extent alterations in renal artery myogenic constriction are involved in development of renal damage during aging is unknown. Therefore, we studied two strains of fawn-hooded rats, which differ in expression of hypertension and chronic renal failure.Methods:Ten-week-old fawn-hooded hypertensive (FHH) and fawn-hooded low blood pressure (FHL) rats were followed for SBP and proteinuria for 1 year. At 52 weeks of age, the kidney was removed and studied for focal glomerulosclerosis (FGS) and glomerular cross-sectional area, and myogenic constriction of isolated small renal arteries in a vessel perfusion set up. Renal myogenic constriction and FGS were additionally determined in 10-week-old fawn-hooded rats.Results:At young age, fawn-hooded rats did not differ in SBP, FGS, and urinary protein excretion, but renal artery myogenic constriction already was significantly smaller (approximate to 50%) in FHH compared with FHL rats. Aging in fawn-hooded rats was associated with increase in SBP and urinary protein excretion and loss of renal artery myogenic constriction. These changes occurred in both fawn-hooded strains, although that in FHH rats the onset of hypertension occurred earlier and the increase in proteinuria by far exceeded (>4 times) that observed in FHL rats, and came along with 5.5 times increase in FGS and 1.3 times increase in glomerular cross-sectional area and significantly less preserved renal artery myogenic constriction in FHH rats.Conclusion:Better preservation of renal myogenic constriction protects the kidney from age-related hypertensive renal damage in the fawn-hooded rat.