The composition and flow of parotid saliva during acute hyperkalaemia in sodium-deficient sheep

Sheep were infused intravenously with 0-43 M-KCl at 2 ml/min for 2 hr while they were either sodium-replete or sodium-deficient after the unilateral loss of parotid saliva for 18 hr or 3 days. Salivary flow was depressed during potassium infusion and the flow rates observed at maximum hyperkalaemia were similar in all three states of sodium balance despite the large differences in flow rate before potassium infusion. The fall in salivary Na/K ratio during potassium administration was diphasic, the initial decline being slow and followed by a more rapid fall in the ratio. The duration of the initial period of slow decline in this ratio ranged from 75-105 min, 45-60 min, and about 15 min in the sodium-replete, mildly sodium-deficient and severely sodium-deficient states respectively. The decline in salivary flow during sodium depletion was associated with decreasing salivary bicarbonate concentration and increasing salivary phosphate and hydrogen ion concentrations with the concentration of chloride showing no consistent trend. During acute hyperkalaemia the chloride and phosphate concentrations were negatively correlated with salivary flow, the bicarbonate concentration was positively correlated with flow and the hydrogen ion concentration was unaltered. The sodium concentration of the saliva showed a statistically significant correlation with flow only when the sheep were severely sodium-deficient.