Resetting of renal blood flow autoregulation in spontaneously hypertensive rats

Abstract

Renal blood flow (RBF) autoregulation was examined in untreated 10- and 40-wk-old spontaneously hypertensive rats (SHR) [mean arterial pressure (MAP) 125 +/- 4 and 167 +/- 7 mmHg] and in captopril-treated (7 days) 10- and 40-wk-old SHR (88 +/- 7 and 112 +/- 5 mmHg). Age-matched Wistar-Kyoto rats (WKY) were used as controls (MAP 91 +/- 3 and 104 +/- 2 mmHg). The study was carried out in rats with and without acute uninephrectomy. In 10-wk-old acutely uninephrectomized animals, the lower pressure limit of autoregulation was 78 +/- 4 mmHg in WKY, 102 +/- 5 mmHg in SHR (P less than 0.02), and 78 +/- 7 mmHg in captopril-treated SHR (P greater than 0.10). The renal vascular resistance (RVR) was significantly elevated at the lower pressure limit of RBF autoregulation in untreated SHR (P less than 0.02) but became normal after treatment (P greater than 0.10). Neither uninephrectomy nor variation of RBF between different batches seemed to influence the lower pressure limit of RBF autoregulation. In 40-wk-old acutely nephrectomized animals, the lower pressure limit of RBF autoregulation in WKY was 85 +/- 4 mmHg, 128 +/- 3 mmHg in SHR (P less than 0.001), and 101 +/- 5 mmHg in captopril-treated SHR (P less than 0.01). RVR at the lower pressure limit was increased in untreated SHR (P less than 0.01), but fell to normal values during captopril treatment. Neither the uninephrectomy nor variation of RBF between different batches of rats seemed to influence the lower pressure limit of RBF autoregulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced myogenic responsiveness of renal interlobular arteries in spontaneously hypertensive rats.

“…2 In previous studies with the isolated perfused hydronephrotic kidney, we demonstrated that pressure-induced afferent arteriolar vasoconstriction is reset to higher pressure levels in SHR. 3 In the present study, alterations in the myogenic responsiveness of the intermediate segment of the ILA were observed to occur in this same model.…”

“…2 We have previously demonstrated that myogenic afferent arteriolar vasoconstriction is reset to higher renal arterial pressure (RAP) levels in spontaneously hypertensive rats (SHR). 3 Although the afferent arteriole is primarily responsible for both acute 4 -5 and chronic 6 ' 7 adaptations to elevated RAP, the interlobular artery (ILA) may also contribute to renal autoregulation.…”

NO dependency of RBF and autoregulation in the spontaneously hypertensive rat

“…Changes in perfusion pressure were corrected for by ϳ85-90% under baseline conditions. This finding is in contrast to reports showing almost perfect autoregulatory efficiency in the SHR (16). The present data set was subjected to the same calculation method described previously (27), which avoids interobserved error, as has been recently emphasized by others (9).…”

“…On the one hand, renal NO dependency has been reported to be increased (29), which could lead to a diminished autoregulatory efficiency. On the other hand, RBF autoregulation is preserved relatively well in the SHR, albeit at a higher range of perfusion pressures (1,16,21). The influence of NO on autoregulation in this model has been investigated in one study (19).…”

Effects of allisartan, a new AT1 receptor blocker, on blood pressure and end-organ damage in hypertensive animals

“…The activity of the renin-angiotensin system (RAS) is normal or low in SHR [31] . However, the BP can be lowered by the commonly used ACE inhibitor and AT 1 receptor blockers [32,33] . This is consistent with our present results that allisartan reduced BP in SHR.…”