Abstract P151: Salt Sensitivity in Male and Female C57BL/6J Mice: Role of Renal Angiotensin and Dopamine Receptors and Sodium Transporters

Abstract

To test if there is a sex difference in the salt sensitivity of C57Bl/6J mice, we studied blood pressure (BP), renal dopamine receptors, and sodium transporters in response to high salt diet (4% NaCl, 1 wk) and candesartan. Similar to males, the night-time systolic BP (SBP, telemetry, n=4) in females started to increase on day 1, peaked on day 2 (130±1 vs 117±1, mm Hg) and remained at high levels (126±1); the daytime SBP started to increase on day 2 that became significant on day 6 (124±1 vs 111±1). The high salt-diet induced-increase in SBP was prevented by candesartan (1 mg/kg, 1 wk, subcutaneously via osmotic mini-pump) (82±3 vs. 117±2 in males; 86±2 vs. 121±1 in females, under anesthesia, n=5/group). There were no sex differences in the SBP response to diet and candesartan, food and water intakes, urinary excretions of water and electrolytes, and serum concentrations of creatinine and electrolytes on high and normal salt diet. In females fed a high salt diet, candesartan increased renal D 1 R (151±12, immunoblotting, % of control, n=5/group) and D 5 R (156±5) but not D 2 R, D 3 R , or D 4 R protein expression, increased renal mRNA expression of D 1 R(160±17) but not D 5 R (real-time PCR), and decreased the renal protein expressions of sodium-hydrogen exchanger isoform 3 (36±6), sodium-potassium-2 chloride cotransporter (8±2), sodium-chloride cotransporter (30±3), and α (55±4), β (60±8) and γ (9±1) epithelial sodium channel, but not type 2 sodium phosphate cotransporter and α1Na + K + ATPase. Those changes were also seen in males except that renal D 1 R protein expression was not increased. Under normal salt intake, AT 1A R KO females (C57Bl/6J background) had increased renal protein expressions of D 1 R (152±8), D 5 R (131±6), and D 4 R (114±4), but not D 2 R and D 3 R; renal protein expressions of sodium-hydrogen exchanger isoform 3 (47±8), sodium-potassium-2 chloride cotransporter (52±11), and α (42±9) and γ (46±7) epithelial sodium channel were decreased. We conclude that the increase in BP caused by high salt diet and the effect of AT 1 R blockade on BP, renal dopamine receptors and sodium transporters are similar in male and female C57Bl/6J mice . The consequences of the sex-related differential regulation of D 1 R and D 5 R, in pathophysiology, other than BP, remain to be determined.