Body Fluid Distribution in Two-Kidney, One Clip and One-Kidney, One Clip Hypertension in Rats

The distribution of body fluid volumes was studied in two-kidney, one clip (2K1C) and one-kidney, one clip hypertension (1K1C) rats (following of nomenclature of American Heart Association). Plasma volume (PV), extracellular fluid volume (ECF) and total body water (TBW) were measured on days 1, 7 and 28 after renal artery stenosis. Body fluid volumes were determined with the isotope dilution mothod : (1) radioiodinated serum albumin for PV : (2) 35SO4 for ECF : (3) tritiated water for TBW. Mean arterial pressure (MAP) and plasma renin activity (PRA) were also examined in relation to changes in the fluid distribution. Measurements were performed in conscious state.The body fluid volumes in 2K1C rats did not differ from those in the sham controls on any experimental day except for a decrease in PV of the clipped rats on day 1. MAP in 2K1C rats increased significantly (p < 0.05) only on day 28. In 1K1C rats, a tendency of an increase in PV and ECF on early days was followed by a significant elevation in ECF on day 28 (p < 0.05). MAP in the clipped rats was higher than that in the controls on days 7 and 28.In common with 2K1C or 1K1C, there were no significant differences in PRA between the clipped rats and the controls.These results suggest that : (1) alterations of body fluid volumes may not be involved directly in the development and maintenance of hypertension in 1K1C rats and in 2K1C rats : (2) judging from PRA levels, the renin-angiotensin system may not play a significant role in 1K1C and 2K1C rats.