ABSTRACT
We investigated the effects of low ouabain concentrations on systolic (SAP) and diastolic (DAP) arterial pressures and on pressor reactivity in 3-month-old male spontaneously hypertensive rats (SHR). Arterial blood pressure (BP) and pressor reactivity to phenylephrine (PHE) were investigated before and after 0.18 ìg/kg ouabain administration (N = 6). The influence of hexamethonium (N = 6), canrenone (N = 6), enalapril (N = 6), and losartan (N = 6) on ouabain actions was evaluated. Ouabain increased BP (SAP: 137 ± 5.1 to 150 ± 4.7; DAP: 93.7 ± 7.7 to 116 ± 3.5 mmHg; P<0.05) but did not change PHE pressor reactivity. Hexamethonium reduced basal BP in control but not in ouabain-treated rats. However, hexamethonium + ouabain increased DAP sensitivity to PHE. Canrenone did not affect basal BP but blocked ouabain effects on SAP. However, after canrenone + ouabain administration, DAP pressor reactivity to PHE still increased. Enalapril and losartan reduced BP and abolished SAP and DAP responses to ouabain. Enalapril + ouabain reduced DAP reactivity to PHE, while losartan + ouabain reduced SAP and DAP reactivity to PHE. In conclusion, a small dose of ouabain administered to SHR increased BP without altering PHE pressor reactivity. Although the renin-angiotensin system (RAS), Na+ pump and autonomic reflexes are involved in the effects of ouabain on PHE reactivity, central mechanisms might blunt the actions of ouabain on PHE pressor reactivity. The effect of ouabain on SAP seems to depend on the inhibition of both Na+ pump and RAS, whereas the effect on DAP seems to depend only on RAS.
Subject(s)
Animals , Male , Rats , Enzyme Inhibitors/pharmacology , Hypertension/chemically induced , Ouabain/pharmacology , Renin-Angiotensin System/drug effects , Sodium-Potassium-Exchanging ATPase/antagonists & inhibitors , Antihypertensive Agents/pharmacology , Hypertension/prevention & control , Phenylephrine/pharmacology , Rats, Inbred SHR , Renin-Angiotensin System/physiologyABSTRACT
The changes of Na+ -pump., and Na+, K+ and Mg2+ ions within erythrocytes were studied during treating supraventricular tachyrhythmia (SVT) by Verapamil (VR). The levels of Na+, K+ and Mg2+ within erythrocytes of 30 normal people were 77.9?2.1, 172.5?3.8 and 16.4? 0.4?mol/g Hb respectively and the level of Na+- pump of the membrane of erythrocytes was 43.9? 6.1 ?mol Pi/g Hb/h. The average levels of Na+, K+ and Mg2+ within erythrocytes of 53 SVT were 83.715.0, 143.2?12. 5, 12.6?0.5 umol/g Hb and the level of Na+-pump was 65.115.2 ?Pi/g Hb/h. After VR treatment, the level of Na+ within erythrocytes was 'obviously higher than that of normal person (P