Using the xenon-133 washout technique, the renovascular response to intrarenal infusions of 3 and 30 mumol/min noradrenaline in four baboons with dietary-induced hypercholesterolaemia was measured. 2. The degree of reduction in cortical blood flow rate during an intrarenal infusion of 3 mumol/min noradrenaline in the four hypercholesterolaemic baboons was not significantly different from that in normocholesterolaemic baboons. However, a significant difference in the degree of reduction in cortical blood flow rate was found with the 30 mumol/min noradrenaline infusion (P less than 0.05). 3. The mean arterial blood pressure of the four animals was significantly higher (P less than 0.001) than the mean blood pressure in baboons used in this laboratory for other experiments. 4. These results have shown that baboons with dietary-induced hypercholesterolaemia have an enhanced renovascular sensitivity to exogenous noradrenaline. However, the possibility that this enhanced sensitivity was due to the associated hypertension cannot be excluded.
