Effect of mono- and bilateral nephrectomy on efferent sympathetic nerve activity to the kidneys in the rat

Abstract

The object of this study was to verify if the removal of one or of both normal kidneys is accompanied by alterations in the efferent sympathetic nerve activity to the kidneys (RSNA). RSNA, blood pressure (BP), heart rate (HR), rate of breathing (RB), and rectal temperature (T) were continuously monitored for five hours in three groups of pentobarbital anesthetized, spontaneously breathing Sprague-Dawley (250–300 g) rats: group 1 (n = 5), both kidneys intact; group 2 (n = 5) and 3 (n = 5), left kidney excised. In addition in group 3, after one hour of control recording, the right renal hylus was tied to produce a complete, reversible, ischemia of the right kidney (functional right nephrectomy: FRN). In group 3 the RSNA was recorded continuously for one hour before, during three hours of FRN and for one hour after. In group 1 and 2, while BP, HR and RB remained fairly constant, RSNA progressively increased from a control value of 22.3 ± 2.1 and of 26.7 ± 1.2 imp/sec at time 0 (mean ± S.E.) to 122.9 ± 13.6 and to 80.9 ± 10.7 imp/sec at time 5 h respectively. In contrast in group 3 RSNA progressively declined during the three hours of FRN, from a control value of 39.1 ± 3.1 at time 1 h (beginning of FRN), to 13.7 ± 2.6 imp/sec at time 4 h (end of FRN period), while BP and HR did not exhibit any significant alterations. The reopening of the right renal hylus was followed by a hypertensive and tachycardic episode, (described in a separate communication), and by short lasting complex alterations of RSNA. These data show that the removal of both kidneys is accompanied by a clear progressive reduction in the RSNA, thus suggesting that the normal kidneys exert a supportive and facilitatory role on efferent sympathetic activity directed back to the kidneys either through a reflex mechanism initiated by afferent renal nerves or substances released from the kidneys.