AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 5 624-R633, Copyright © 1985 by American Physiological Society
Formulating and evaluating quantitative models of control of sodium stores
F. H. Daniels, S. Cortell and E. F. Leonard
Numerous factors that influence sodium handling have been identified, and
many have been studied in minute detail; however, relatively little
information is available regarding either the steady-state relationship
between dietary sodium intake and sodium stores or the transient response
of intact animals to challenges to sodium homeostasis. In this paper the
principles of elementary feedback control theory have been used both to
obtain and analyze quantitative models of the feedback control of sodium
stores. It has been assumed that the sodium content of the body determines
the rate of urinary sodium excretion, and a mass balance has been used to
obtain differential equations that describe the dynamics of sodium stores.
Both first- and second-order models are considered, and their predictions
for both steady states and transients are compared critically with
observations from the literature, using data from human studies whenever
possible. The results indicate that a relatively simple proportional
feedback controller describes most available data well; however, gaps in
the available information are identified, and opportunities for future
experimental investigation are described.
