Renal dopaminergic defect in C57B1/6J mice

Escano CS, Armando I, Wang X, Asico LD, Pascua A, Yang Y, Wang Z, Lau YS, Jose PA. Renal dopaminergic defect in C57Bl/6J mice. Am J Physiol Regul Integr Comp Physiol 297: R1660-R1669, 2009. First published September 2, 2009; doi: 10.1152/ajpregu.00147.2009.--The C57Bl/6J mouse strain, the genetic background of many transgenic and gene knockout models, is salt sensitive and resistant to renal injury. We tested the hypothesis that renal dopaminergic function is defective in C57Bl/6J mice. On normal NaCl (0.8%, 1 wk) diet, anesthetized and conscious (telemetry) blood pressures were similar in C57Bl/6J and SJL/J mice. High NaCl (6%, 1 wk) increased blood pressure ([approximately equal to]30%) in C57Bl/6J but not in SJL/J mice and urinary dopamine to greater extent in SJL/J than in C57B1/6J mice. Absolute and fractional sodium excretions were lower in SJL/J than in C57Bl/6J mice. The blood pressure-natriuresis plot was shifted to the right in C57Bl/6J mice. Renal expressions of [D.sub.1]-like ([D.sub.1]R and [D.sub.5]R) and angiotensin II [AT.sub.1] receptors were similar on normal salt, but high salt increased [D.sub.5]R only in C57B1/6J. GRK4 expression was lower on normal but higher on high salt in C57Bl/6J than in SJL/J mice. Salt increased the excretion of microalbumin and 8-isoprostane (oxidative stress marker) and the degree of renal injury to a greater extent in SJL/J than in C57Bl/6J mice. A [D.sub.1]-like receptor agonist increased sodium excretion whereas a [D.sub.1]-like receptor antagonist decreased sodium excretion in SJL/J but not in C57B1/6J mice. In contrast, parathyroid hormone had a similar natriuretic effect in both strains. These results show that defective [D.sub.1]-like receptor function is a major cause of salt sensitivity in C57B1/6J mice, decreased renal dopamine production might also contribute. The relative resistance to renal injury of C57Bl/6J may be a consequence of decreased production of reactive oxygen species. angiotensin II receptors; dopamine receptors; GRK4; reactive oxygen species doi: 10.1152/ajpregu.00147.2009