DOPAMINE PRODUCTION BY ISOLATED GLOMERULI AND TUBULES FROM RAT KIDNEYS

To locate the sites of dopamine (D) production in rat renal cortex, glomeruli and proximal tubules were separated by sieving or centrifugation in Percoll after collagenase digestion. After centrifugation layer I contained 60-80% glomeruli and 20-40% tubule fragments, half of which did not stain with alkaline phosphatase, layer II contained 0-5% glomeruli, 10-25% tubule fragments other than proximal tubules and 70-85% proximal tubule fragments. Layer IV contained 85-95% proximal tubules. Gluconeogenic rates were (in .mu.mol/h/g wet weight) as follows: I, 4 .+-. 1; II, 7 .+-. 2; and IV, 16 .+-. 1. Norepinephrine (NE) content was (pmol/g wet weight) I, 310 .+-. 30; II, 540 .+-. 40; IV, 195 .+-. 60. D content was (pmol/g wet weight) I, 26 .+-. 6; II, 46 .+-. 13; IV, 33 .+-. 7. Surgical denervation 4-6 days previously reduced the NE content of layers I and II to 35 .+-. 10 (P < 0.001) and of IV to 60 .+-. 20 (P < 0.05) and the D content of layers I and II to 13 .+-. 6 and 6 .+-. 6 pmol/g, respectively (P < 0.01); D content of layer IV was unchanged. D production from 10-7 M 3,4-dopa was (nmol/g/min) I, 0.2 .+-. 0.03; II, 0.7 .+-. 0.1; IV, 1.0 .+-. 0.04. Dopa consumption was (nmol/g/min) I, 0.6 .+-. 0.1; II, 1.4 .+-. 0.3; and IV, 1.8 .+-. 0.2. Denervation did not change D production or dopa consumption. Glomeruli without arterioles or tubules, obtained by sieving, contained no D or NE and did not produce D from dopa. Proximal tubules produced at least 5 times more D from dopa than glomeruli and distal tubules. Renal nerves did not contribute significantly to D production. There was no evidence of specific D-containing nerves associated with rat glomeruli.