Specific Features of Electrolyte Excretion at the Early Stages of Arterial Hypertension in SHR Rats.

Daytime and nighttime systolic and diastolic BP was recorded in 23-week-old SHR and Wistar rats by telemetric monitoring. Urine concentrations of sodium, potassium, and calcium were determined in SHR rats during of light (07.00-19.00 h) and dark hours (19.00-07.00 h) at the age of 18, 19, 20, 21, 22, and 23 week; 23-week-old Wistar rats were used as the control. At early stages of the experiment, urine sodium concentration was elevated in SHR rats both at daytime and at night. Thereafter, this value declined and by 22-23 week was significantly lower than in normotensive Wistar rats, but only during daytime. Daytime potassium concentration significantly surpassed the control level during weeks 18-19 of the experiment, but later, a tendency to a decrease in this parameter was observed. Daytime calcium content in SHR rats did not significantly differ from the control throughout the experiment. At night, this value exceeded the control level by more than 2 times during weeks 18-19, but then returned to the level observed in normotensive animals.