Evidence for Angiotensin-Stimulated Proximal Tubular Fluid Reabsorption in Normotensive and Hypertensive Rats: Effect of Acute Administration of Captopril

1. The effects of captopril on mean arterial blood pressure and proximal tubular fluid re-absorption (J_v) were examined in anaesthetized normotensive rats and in the non-clipped kidneys of two-kidney, one-clip Goldblatt hypertensive rats.

2. In the normotensive animals, captopril reduced arterial blood pressure from 121 ± sd 9 to 106 ± 10 mmHg and J_v decreased from 3.78 ± 0.45 to 2.57 ± 0.58 × 10⁻⁴mm³mm⁻²s⁻¹. Captopril had a greater effect on blood pressure in the hypertensive animals (172 ± 17 reduced to 133 ± 23 mmHg) although the decrease in J_v from 3.62 ± 0.12 to 2.40 ± 0.40 was similar to that observed in normotensive animals.

3. These results provide evidence that, in the anaesthetized rat, angiotensin II contributes to the maintenance of the rate of proximal fluid re-absorption. The magnitude of the angiotensin-stimulated component of proximal fluid absorption is similar in normotensive and two-kidney, one-clip Goldblatt hypertensive rats.