Tubular transport and urinary excretion of phosphate after renal denervation in the anesthetized rat

Abstract

Tubular transport of phosphate (Pi) was studied using clearance and tracer microinjection techniques in Inactin-anesthetized male rats subjected to left kidney denervation. Experiments were conducted in the following groups: i) acute denervation (AD); ii) chronic denervation (CD); iii) acute denervation plus thyroparathyroidectomy (AD + TPTX); iv) microinjection with AD. Besides a marked diuresis and natriuresis with no difference in GFR between innervated (inn) and denervated (den) kidneys, unilateral renal denervation resulted in an increased urinary excretion and decreased tubular reabsorption of inorganic phosphate. Maximum tubular reabsorption of Pi (TmPi) calculated per unit GFR was (means +/- SE): AD, inn: 2.38 +/- 0.04, den: 1.98 +/- 0.06 mumol/ml; CD, inn: 2.66 +/- 0.10, den: 2.19 +/- 0.11 mumol/ml; AD + TPTX, inn: 4.78 +/- 0.06, den: 4.26 +/- 0.08 mumol/ml. Thus, differences in TmPi between the two sides were of the same magnitude in the three groups. Fractional recovery of 32Pi from microinjections in control (C) and postdenervation (D) periods was: early proximal, C: 53.0 +/- 0.81, D: 61.3 +/- 1.07%; late proximal, C: 77.0 +/- 0.81, D: 70.6 +/- 0.60%; early distal, C: 93.7 +/- 0.75, D: 03.5 +/- 0.72%. It is concluded that renal sympathectomy depresses tubular transport of inorganic phosphate in anesthetized rats by a primary action on the proximal convoluted tubule and with a partial compensation in the loop of Henle.