Plasma renin activity, angiotensin II, and aldosterone after mental arithmetic

Abstract

Plasma renin activity (PRA) and the concentration of plasma angiotensin II and aldosterone, blood pressure, heart rate, serum electrolytes and some haemato-logical parameters were measured in six male subjects who carried out exercises in mental arithmetic for a period of 20 min. After this mental exercise the PRA and angiotensin II values increased significantly, but plasma aldosterone showed a tendency to decrease. The highest mean increases in PRA (560%, P <0.02) and in angiotensin II (660%, P<0.001) were found 15 min after the challenge. Immediately after the mental activity systolic blood pressure was increased by 10.3 % (P<0.005), diastolic blood pressure by 10.3% (P<0.02) and heart rate by 19.7% (P< 0.001) over the pre-test values. There were no significant changes in serum electrolyte levels until 1 and 2 h after the exercises, at which time the serum potassium values were slightly, but significantly (P < 0.005) decreased. There were no significant changes in the haematological parameters studied (blood erythrocytes, leucocytes, haemoglobin, haematocrit, and the volume, amount of haemoglobin, and haemoglobin concentration of the red cells). A positive correlation (r = 0.9389, P<0.01) was found between the increases observed in the PRA and in heart rate. The changes found in PRA and in the concentration of plasma angiotensin II after these exercises in mental arithmetic resemble those found previously, after physical and heat stress.

Key Words:

• blood pressure
• heart rate
• haematological parameters
• serum potassium
• serum sodium