Understanding the contribution of Guyton's large circulatory model to long-term control of arterial pressure.

With the publication in 1972 of a large computer model of circulatory control, Guyton and colleagues challenged the then prevailing views on how blood pressure and cardiac output were controlled. At that time, it was widely accepted that the heart controlled cardiac output and that peripheral resistance controlled arterial blood pressure. By incorporating the empirically demonstrated concepts of blood flow autoregulation and the pressure-natriuresis relationship into their mathematical model, Guyton and colleagues were able to develop a number of revolutionary concepts. Guyton's circulatory model was particularly instrumental in exploring the linkage between blood pressure and sodium balance and in demonstrating an overriding importance of renal salt and water balance in setting the long-term blood pressure level. In both the model and experimental data, any long-lasting imbalance between salt intake and salt excretion leads to a progressive alteration of the degree of filling of the vascular system and thus to parallel changes in blood pressure. In turn, changes in blood pressure alter sodium excretion, opposing the initial salt imbalance. Although Guyton's model does not include the most recent cardiovascular discoveries, the concepts underlying the basic functioning of the cardiovascular system can serve as a well-built basis for the development of new, large and integrative cardiovascular models.