1. The activity of ouabain-sensitive Na + ,K + -dependent ATPase and ouabain-sensitive ATPase was measured in the microsomal fractions of kidney, liver and heart tissue of Sprague-Dawley rats treated with DOCA (10 mg day −1 kg −1 for 6 days, systolic blood pressure 143 ± 13 mmHg, n = 9) or 6 α-methylprednisolone (100 mg day −1 kg −1 for 6 days, systolic blood pressure 140 ± 19 mmHg, n = 9) and of a control group (systolic blood pressure 124 ± 12 mmHg, n = 9). 2. In the kidney, the ouabain-sensitive Na+,K + -ATPase activity (μmol of phosphate h −1 mg −1 of protein) was increased in the DOCA-treated (33.0 ± 6.9) and in the prednisolone-treated groups (30.8 ± 6.9) compared with that in the control group (26.4 ± 3.4) ( P < 0.05). In the liver, the ouabain-sensitive Na + ,K + -ATPase activity was elevated in the prednisolone-treated animals only (4.8 ± 1.3 vs 3.1 ± 0.8 in the controls, P < 0.025). The ouabain-sensitive Na + ,K + -ATPase activity in heart tissue was similar in all three groups. The ouabain-insensitive ATPase activity was not altered by DOCA or prednisolone in the tissues studied. 3. In a separate study, the activity of the ouabain-sensitive Na + ,K + -ATPase in erythrocyte ghosts was found to be elevated in 10 patients with Cushing's syndrome (0.91 ± 0.35 μmol of phosphate h −1 mg −1 of protein) compared with five patients with primary aldosteronism and compared with 12 normotensive control subjects (0.38 ± 0.08) ( P < 0.005). 4. These data demonstrate an increased Na-K pump activity in the kidney in mineralocorticoid-induced hypertension. Glucocorticoids in addition activate the Na-K pump in a variety of other tissues. This could partially explain the redistribution of volume from the intracellular to the extracellular space.
1. We have investigated the function of the Na + -K + pump in the erythrocytes of patients with various types of hypertension by measuring the activity of ouabain-sensitive Na + -K + -dependent ATPase and ouabain-insensitive ATPase in the erythrocyte ghosts of these patients. 2. Mean Na + -K + -ATPase activity was increased threefold in six patients with Cushing's syndrome and hypertension (0.985 ± sd 0.288 μmol of phosphate h −1 mg −1 ) compared with that in 49 control subjects (0.334 ± 0.147 μmol of phosphate h −1 mg −1 ) ( P <0.0025), but not in four patients with primary aldosteronism (0.278 ± 0.108 μmol of phosphate h −1 mg −1 ). 3. Na + -K + -ATPase activity slightly exceeded the control range in 57 patients with primary hypertension (0.410 ± 0.245 μmol of phosphate h −1 mg −1 ; P <0.025) and in 12 patients with renal hypertension (0.475 ± 0.250 μmol of phosphate h −1 mg −1 ) ( P <0.025). 4. There was no difference in ouabain-insensitive ATPase between the controls and the different types of hypertension. 5. The data support the hypothesis of an activation of the Na + pump in patients with glucocorticoid excess. This helps to explain previous observations of a redistribution of sodium and water to the extracellular compartment in experimental glucocorticoid-induced hypertension.
1. Plasma renin concentration (PRC) in newborns greatly exceeded PRC in children and adults. PRC in cord plasma of newborns was higher than peripheral venous PRC in their mothers. PRC in the newborns increased further in the first 48 h post partum and then gradually decreased. 2. The mean PRC of healthy children and adults on free sodium intake decreased with age by an exponential function. 3. The absolute increase of PRC in response to upright posture (PRC upright — PRC recumbent ) decreased with age. The relative increase of PRC in response to upright posture (PRC uprjght :PRC recumbent ) remained unchanged with age, the PRC in upright posture being about twice the basal PRC in all age groups.