Kinetics of sodium in rabbit arterial wall: inability of aldosterone to alter extra to intracellular distribution.

Transport rate constants (kij) describing the kinetics of Na exchanges in isolated rabbit aorta wall were determined by a previously established method involving the use of 22Na as a tracer and digital computer simulation without recourse to ancillary chemical measurements of extracellular space. A three compartment model consisting of (i) extracellular, (ii) intracellular and (iii) subcellular spaces (compartments) was found to describe adequately the kinetics of 22Na. Normative values for intercompartmental kij and extra to intracellular Na ratio were established. It appears that the Na extracellular space in rabbit arterial wall is larger than that in dog or rat arterial wall. Surprisingly, at variance with several tissues of different species (dog, rat, mouse and human tissues), aldosterone did not influence the extra to intracellular distribution of Na. The findings are interpreted in the light of results obtained previously by other workers using entirely unrelated methodologies and suggest that species difference is an important factor to consider when studying effects of aldosterone on tissue electrolyte distribution in the rabbit.