Renal Vascular Resistance in Spontaneously Hypertensive Rats

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Abstract
The renal vascular beds of one spontaneously hypertensive rat (SHR) and one matched normotensive control rat (NCR) were perfused with oxygenated plasma substitute in 27 paired expts. Pressure‐flow curves indicated that the renal vascular resistance is lower in SHR than in NCR during maximal dilatation, in contrast to the situation in other major circuits, while the SHR renal resistance vessels are less distensible than those of NCR.–Graded noradrenaline (NA) infusions showed that the NA threshold does not differ significantly between the two groups, but SHR displays a steeper dose‐response curve and an increased maximal pressor response as compared to NCR.–The results suggest an increased media thickness in the SHR renal resistance vessels, raising their wall/lumen ratio, “reactivity” and maximal contractile strength but reducing their distensibility. However, while the thickened vascular walls in other major circuits encroach upon the lumina, even at maximal dilatation (Folkowet. al.1970 a, b), they are in the kidneys combined with increased vascular lumina. This implies a larger renal blood supply in SHR than in NCR at very low level of vascular tone while the reverse is true at enhanced tone, due to the steeper resistance curve in the SHR.