Basal norepinephrine overflow into the renal vein: effect of renal nerve stimulation.

Abstract

In order to determine whether the fraction of norepinephrine released from the renal nerves that escapes into the circulation can be used an an index of renal sympathetic nervous activity, arterial and renal vein plasma norepinephrine concentrations were measured by a radioenzymatic technique along with renal blood flow in anesthetized dogs under control conditions and during electrical renal nerve stimulation. In 25 animais studied under conditions of normal sodium balance, plasma norepinephrine in the renal vein, 198 ± 26 pg/ml, was significantly higher than in arterial blood, 102 ± 10 pg/ml (P < 0.001). In five dogs, electrical stimulation of the renal nerves (12 V, 3 ms) at frequencies of 0.5, 2,6, 12, and 18 Hz for 1 min was associated with increased norepinephrine concentration in renal venous plasma and an increase in the calculated renal norepinephrine overflow. There was a significant linear relationship between the frequency of stimulation and norepinephrine overflow into the renal vein in each animal, but there was also a significant interanimal variation in the slope of this relationship (P <0.01). Electrical stimulation at a frequency of 2 Hz significantly decreased renal blood flow (-24 ± 7 ml/min, P < 0.01). The maximal effect was achieved at 6 Hz (-66 ± 11 ml/min). The data indicate that there is a base-line overflow of norepinephrine into the renal venous blood of the dog that increases with increasing frequency of electrical nerve stimulation. They suggest that measurements of norepinephrine overflow into the renal vein may be used to assess the activity of the renal sympathetic nervous system. renal blood flow; catecholamines; renin; dog Submitted on January 10, 1980 Accepted on April 29, 1980