Historical perspective of cardiorenal integration

1. Early research on blood volume as an independent parameter affecting kidney function took the approach that the sensors must be located in the most compliant, that is the reservoir portion, of the cardiovascular system. This encompasses the great veins and the cardiac atria. 2. Small changes in volume were shown not to affect the compliance of this reservoir and messages from the atrial receptor network were shown to travel in the vagus nerve and to control urine volume by antidiuretic hormone. 3. Although greatly affected by the water immersion stimulus, sodium excretion was not as dependent on vagus integrity. The ensuing search for the natriuretic arm of the blood volume mechanism persisted for the next 20 years. 4. Finally, one aspect of the elusive natriuretic factor was found exactly where theory had suggested, namely the most distensible part of the system, in specialized granules in the cardiac atria.