Buffer effect, secretion rate, pH and electrolytes of stimulated whole saliva in relation to the renin-aldosterone system.

The aim of this investigation was to study the relationship between the activity of the renin-aldosterone system and the buffer effect, secretion rate and electrolyte concentration of stimulated saliva in healthy subjects. Based on the results of previous salivary tests, 10 subjects with "low" (group A) and 10 subjects with "high" (group B) buffer effect and secretion rate of stimulated whole saliva were studied. Samples of stimulated whole saliva, blood and urine were collected on three occasions with one week intervals. For saliva, buffer effect, secretion rate, pH, Na+ and K+ concentrations, and Na+/K+ ratio were determined as were plasma renin activity (PRA), plasma concentration of aldosterone, and concentration of Na+ and K+ in serum, and Na+, K+ and creatinine in urine. The daily sodium and potassium intake was also calculated but did not differ between the groups. With the exception of K+ concentration, which was significantly higher, all salivary values of group A were significantly lower. In group A there was a relationship between PRA and plasma concentration of aldosterone, on the one hand, and buffer effect, secretion rate, and salivary K+ concentration, on the other. This relationship could not be demonstrated in group B. A possible explanation is that the higher secretion rate of the latter group obscured the effect of the renin-aldosterone system.