Dopamine production by isolated glomeruli and tubules from rat kidneys

Publisher Website
Google Scholar
Abstract
To locate the sites of dopamine (D) production in rat renal cortex, we separated glomeruli and proximal tubules 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 (micromoles per hour per gram wet weight) as follows: I, 4 ± 1; II, 7 ± 2; and IV, 16 ± 1. Norepinephrine (NE) content was (picomoles per gram wet weight) I, 310 ± 30; II, 540 ± 40; IV, 195 ± 60. D content was (picomoles per gram wet weight) I, 26 ± 6; II, 46 ± 13; IV, 33 ± 7. Surgical denervation 4–6 days previously reduced the norepinephrine 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-dihydroxyphenylalanine (DOPA) was (nanomoles per gram per minute) I, 0.2 ± 0.03; II, 0.7 ± 0.1; IV, 1.0 ± 0.04. DOPA consumption was (nanomoles per gram per minute) 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. We conclude that proximal tubules produced at least five times more D from DOPA than glomeruli and distal tubules. Renal nerves did not contribute significantly to D production. We found no evidence of specific D-containing nerves associated with rat glomeruli.