Fig. 3.

Dietary K⁺ maneuvers induce polyuria. A: diagram indicating the type of cage and diet for each maneuver. Throughout the telemetry experiment, mice were maintained in telemetry cages and fed pellet diet (P) ad libitum. On days 11–14, their drinking water was switched from free water to 1% saline. For the 5- and 10-day urine and whole blood experiments, mice were maintained on the pellet diet. Then, 24 h before placement in metabolic cages, mice were introduced to the gel diet [access to both pellet and gel diets (P&G)] and next placed in metabolic cages exclusively on the gel diet (G) and acclimatized for 24 h, and urine was collected for 24 h. *Time point when mice were euthanized and whole blood was collected. For the diuretic experiments, mice were placed in the metabolic cages and on exclusive gel diets on day 10. B: mice were maintained on varying K⁺ diets, and 24-h intakes and outputs (I/O) were obtained on days 5 and 10. Mice maintained on the K⁺ basic diet had decreased consumption at day 5 compared with mice on the other diets, but by day 10 this difference was attenuated. C: 24-h urine trends were similar on both days 5 and 10. Urinary K⁺ (mmol/day) was appropriately decreased with the low-K⁺ diet. The KCl diet had more urinary K⁺ excretion than the K⁺ basic diet; both were appropriately increased compared with the control (Ctrl) diet. D: urinary Na⁺ (mmol/day) was significantly decreased on day 5 with the low-K⁺ diet compared with control diet-fed mice. On day 10 only the K⁺ basic diet significantly increased urine Na⁺ (mmol/day) compared with control. Mice maintained on K⁺ basic and KCl diets had significant differences in daily Na⁺ excretion. E: on day 5, mice fed the high-K⁺ diets had increased water intake compared with control; by day 10, mice fed the low-K⁺ diet also began to have increased water intake. F: on day 5, mice fed the low-K⁺ diet had a decrease in urine volume, whereas mice fed the KCl diet had an increase in urine volume. On day 10, urine volume was significantly increased by low-K⁺ and high-K⁺ diets compared with the control diet. G: on day 10, only the low-K⁺ diet significantly decreased urine osmolality (osms) compared with the control diet. Day 5: n = 5–6 mice per diet; day 10: n = 16–18 mice per diet. One-way ANOVA with Sidak’s post hoc analysis, *P ≤ 0.05 and **P ≤ 0.01, significant difference from the control diet and ^φsignificant difference between the K⁺ basic and KCl diets.