1. Mean arterial pressure, cardiac output (electromagnetic flow-meter) and regional blood flows (15 μm radioactive microspheres) were measured repeatedly in eight dogs receiving a salt and water load after renal mass reduction as well as in six control animals.
2. As previously observed, hypertension developed in the salt-loaded dogs with an initial increase in cardiac output followed by a secondary rise in total peripheral resistance.
3. Much of the early increase in cardiac output was distributed to the skeletal muscle vascular bed.
4. Total peripheral resistance changes did not reflect the resistance of individual vascular beds in the early stages of salt and water load hypertension; indeed, resistance in the muscle vascular bed was decreased and that in the splanchnic area and the bone increased on the first day of salt and water load when total peripheral resistance was unchanged.