COMPARATIVE-STUDY OF THE EFFECTS OF OUABAIN AND DIGOXIN ON BLOOD-PRESSURE OF RATS

Objective To compare the effect of ouabain on the blood preasure of ra ts with that of digoxin to find the evidences of the relationship betw een endogenous ouabain (EO) and development of hypertension. Methods S prague-Dawley rats, which were divided into 3 groups were infused with ouabain (23.75 mu g.kg(-1)/day, i.p.), digoxin (36.84 mu g.kg(-1)/day , i. p.) and normal saline (NS) once a day respectively. Systolic bloo d pressure and body weight were recorded weekly. Five weeks later, rat s of ouabain group were randomly assigned to three infusion subgroups: Oc group, continued with ouabain infusion: Od group, added digoxin (7 3.68 mu g.kg(-1)/day, i. p.); end Os group, stopped administration of ouabain. Another week later, direct blood pressure was recorded in aor ta. Systolic and diastolic cardiac function, plasma renin activity and aldosterone levers of all the measured. Results After a latent period of one week, blood pressure of Ouabain group increased significantly [95.4 +/- 11.8 mmHg (1 mmHg = 0.133 kPa) at the beginning of the exper iment vs 122.5 +/- 16.9 mmHg at the end of week 6, P < 0.05] with norm al plasma renin activity and higher aldosterone (1.28 +/- 0.45 ng/ml v s 0.69 +/- 0.27 ng/ml, P < 0.05). The blood pressure decreased after e ither withdrawal of ouabain or addition of digoxin (116.3 +/- 14.4 mmH g vs 100 +/- 10.7 mmHg, P < 0.05; 123.9 +/- 13.9 vs 103.3 +/- 10.5 mmH g, P < 0.05, respectively). No difference of blood pressure was found between the digoxin and NS group. Conclusions Our results suggested th at EO might be one of the causes of the development of hypertension. A ldosterone might play some role in the mechanism of ouabain-induced hy pertension. Digoxin can not induce hypertension. There is a great diff erence between the effect of ouabain and digoxin on the blood pressure . Moreover, digoxin can reverse the hypertension induced by ouabain.