Extraneuronal Production of Dopamine by Kidney Slices in Normo and Hypertensive Rats

Abstract

Synthesis of dopamine (DA) was studied in cortical slices of Sprague-Dawley (SD) rat kidneys incubated with L-DOPA (10⁻⁶ M). In morphological studies, formaldehyde-induced histofluorescent deposits were detected at the apical pole of the convoluted parts of the proximal tubules. Elsewhere along the nephron, no positive reaction appeared. DOPA decarboxylase inhibitors suppressed the advent of the deposits, but prior denervation did not. Biochelical studies showed: (a) slices produced 2.2 nmol mg⁻¹ protein, glomeruli 0.2 and cytosol 43 nmol. In absence of L-DOPA or in presence of DOPA decarboxylase inhibitors, DA production was suppressed. Prior denervation did not influence DA production; (b) DA synthesis increased with sodium concentration of the milieu (range 95 to 152 mmol). Adult spontaneously hypertensive rats (SHR) produced less DA than SD or normotensive Wistar-Kyoto, at any sodium concentration from 95 to 142 mmol. This discrepancy could be related to the pathogenesis of hypertension.

Key Words:

• Dopamine production
• kidney
• extraneuronal
• sodium concentration
• SHR