Wallin, Gunnar

Inter‐individual variability in hemodynamic variables appears to be important in human blood pressure regulation. It is not known whether the rat, often used for studies of cardiovascular regulation, exhibits similar inter‐individual variability. In the present study, we evaluated whether inter‐individual variability in cardiac output (CO) and total peripheral resistance (TPR) is similar in humans and in rats, and whether a balance between these variables is similar in the two species. We assessed the relationship between CO and TPR during control conditions in humans (N = 40) and in Sprague‐Dawley rats (N = 16). We further assessed whether the relationship between CO and TPR was altered during acute increases in blood pressure, which were accomplished in humans with acute systemic L‐NMMA (N = 17), and in rats with a DOCA‐salt model (N = 16). Both humans and rats showed marked inter‐individual variability in CO and TPR but low variability in blood pressure. In both species, CO and TPR showed strong inverse correlations during normotension (r 2 = 0.88 (humans) and 0.89 (rats)) and during blood pressure increases (r 2 = 0.91 (humans) and 0.58 (rats)). We conclude that inter‐individual variability CO and TPR, and the balance between these variables, are important aspects of blood pressure regulation in both humans and rats. Supported by NIH HL32352, HL83947, HL64176, UL1‐RR24150 and Swedish Research Council 12170.