Plasma and saliva
Goats. There was a significant (P< 0.01 ) biphasic increase in plasma aldosterone
in the LS group after Na intake was restricted whereas aldosterone
levels did not rise in the AS animals. Peaks of aldosterone secretion coincided
initially with the restriction of Na and then finally with the introduction of
demineralised water in period 6 (Fig. 2). Salivary Na: K ratio was inversely
related (r= -0.74) to plasma aldosterone levels with significant differences
occurring between treatments for both variables during periods 2, 3 and 6
(Fig. 2 ). When aldosterone and salivary Na: K ratio were significantly different
between the AS and LS groups, the average salivary Na and K concentration
and Na:K ratio were 154.2 vs. 115.6 mmol/1, 10.7 vs. 34.1 mmol/1 and
17.3: 1 vs. 5.0: 1, respectively (Fig. 2). Changes in plasma Na and K occurred
during the experiment and they were unrelated to the major shifts of these
ions in saliva (Fig. 2 ).
Cattle. After almost 3 months on the LS diet, salivary Na and K concentration
and Na:K ratio were 134+_4.7 mmol/1, 7.6+0.9 mmol/l and 19.0:1 +_2.1 : 1,
respectively, which approximate normal values, and plasma aldosterone levels
were normal, 29.8 +_ 8.6 pg/ml.