EFFECT OF RENAL DENERVATION ON ELEVATION OF BLOOD-PRESSURE IN COLD-EXPOSED RATS

The objective of this experiment was to determine whether bilateral re nal denervation (RD) prevents the elevation of blood pressure and card iac hypertrophy characteristically induced by chronic exposure to cold . Four groups (nine male rats each) were used. The kidneys of two grou ps were bilaterally denervated, while the remaining two groups were sh am operated. Systolic blood pressures of the four groups, measured ind irectly from the tail, did not differ significantly during the control period and following RD. At this time, 1 RD and 1 sham-operated group was exposed to cold (5 degrees C, 41 degrees F). The remaining RD and sham-operated groups were kept at 25 degrees C. Blood pressure of the cold-exposed, sham-operated group increased significantly during the Ist week of cold exposure (125 +/- 2 mmHg; 1 mmHg = 133.3 Pa), and ros e to 139 +/- 4 mmHg by the 5th week, whereas the blood pressure of the RD group exposed to cold remained at the control level (116 +/- 2 mmH g). Both RD and sham-operated cold-exposed groups developed cardiac hy pertrophy with significantly increased resting heart rates compared wi th controls kept at 25 degrees C. Plasma renin activities and renal no repinephrine content of kidneys of both RD groups at 7 weeks after RD were significantly less than those of sham-operated controls, confirmi ng that renal nerves had been severed. Thus, RD prevented the elevatio n of blood pressure induced by chronic exposure to cold but had no sig nificant effect on cardiac hypertrophy.