Interaction of NaCl and behavioral stress on endogenous sodium pump ligands in rats

Our study investigated the hypothesis that the combination of a high NaCl d iet and social isolation stress would increase systolic blood pressure (SBP ) and endogenous sodium pump ligands (SPL), ouabainlike compound (OLC), and marinobufagenin (MBG). Excretion of MBG and OLC, SBP, and organ weights we re studied in four groups (n = 8) of male Fisher 344 x Norwegian brown rats : controls, socially isolated (Iso), 4% NaCl diet (Salt), and the combinati on of Salt and Iso (Iso+Salt). In Salt, MBG excretion increased by 78% (P< 0.01), whereas SBP and OLC remained unchanged. In Iso, SBP and MBG did not change, but OLC peaked on day 1. In the Iso+Salt, SBP increased by 9 mmHg, MBG excretion increased (42.0 +/- 7.6 vs. 10.0 +/- 1.5 pmol/24 h, P< 0.01), whereas OLC peaked at day 1 (25.0 +/- 2.5 vs. 10.0 +/- 2.0 pmol/24 h, P< 0 .01) and remained elevated. Heart and kidney weights were increased in Salt and Iso+Salt. Aortic weights were increased in Iso and Iso+Salt. Thus a hi gh NaCl intake stimulates MBG excretion, whereas isolation stress stimulate s OLC. The combination of Salt and Iso is accompanied by marked stimulation of both SPL.