Day-night difference in blood pressure and heart rate measurements. Telemetry blood pressure measurements were recorded for 15 s every 2 min and were binned into 12-h light and dark cycle bins for diurnal comparison. Differences between adjacent light and dark cycle 12-h bins were normalized to the mean of the same adjacent 12-h segments. The protocol shown covers 3 days of low-salt (LS) and 20 days of high-salt (HS) diet. Heart rate is plotted for female (A) and male (B) Btg2+/+and Btg2−/− rats along with MAP for females (C) and males (D). The plots depict recordings obtained once every 2 min continuously for 12 h. Data are presented as mean shown in circles and SE shown as bars (only depicted in positive direction). Levels of statistical significance were analyzed by two-way ANOVA. *P < 0.05 (strain comparison), #P < 0.05 (strain by time comparison), ‡P < 0.05 (Sidak post hoc). F, female; HR, heart rate; M, male.