SODIUM AND POTASSIUM BALANCES IN RABBITS WITH ACUTE GOLDBLATT HYPERTENSION

Abstract

The relationships between sodium and potassium balances, plasma renin activity and systolic blood pressure were studied in rabbits during the development of renal hypertension and its reversal.Animals were divided into two groups. Group A consisted of 15 rabbits in which the left renal artery was clipped and the right kidney was left intact. Group B consisted of 15 rabbits in which the left renal artery was clipped 4 weeks after removal of the right kidney. Each animal of both groups was unclipped 2 weeks after the clipping. Animals were studied in metabolic cages for daily sodium and potassium balances, which were estimated on the basis of dietary intake and urinary and faecal excretion. Each animal was given 100g/day of the standard pellets (CR1, Japan Clea Ltd.) and distilled water at libitum. Plasma renin activity was measured before, 14 days after the clipping and 14 days after the unclipping.The main points of the results obtained are as follows : 1) Blood pressure increased rapidly in both groups after the clipping, and it decreased after the unclipping, but still remained above the normal 2 weeks after the unclipping. There was a striking similarity in the course of blood pressure between the two groups.2) After the clipping, cumulative sodium balance became slightly negative in the 1st week and tended to recover in the next week in group A. On the contrary, it became markedly positive in the 1st week and tended to decline in the next week in group B. There were no significant correlations between the cumulative sodium balance and the blood pressure elevation in both groups. After the unclipping, cumulative sodium balance became negative in group B and the negative sodium balance was correlated with the fall in blood pressure.3) There was no significant difference in potassium balance during the periods of both development of hypertension and its reversal between the two groups.4) After the clipping, plasma renin activity showed no significant changes in group A, while it significantly decreased in group B. After the unclipping, no significant changes were seen. There were no positive correlations between plasma renin activity and blood pressure in both groups.5) After the clipping, the faecal sodium excretion and the faecal sodium/potassium (Na/K) ratio decreased in group A and after the unclipping, they recovered.These results suggest that the sodium and potassium metabolism and the renin-angiotensin system do not play a primary role in the pathogenesis of experimental renal hypertension