Chronic exposure to low doses of estradiol-17ß increases blood pressure in young female rats: A possible role for central Endothelin-1

Figures

• 

  Figure 1. Serum estradiol levels in control and E2 treated rats. Adult female Sprague Dawley rats were either sham-implanted or implanted with slow release estradiol 17-β (E2) pellets for 90 days. Estradiol levels were measured by RIA in serum collected from trunk blood at the time of sacrifice at the end of 90 day exposure. *Indicates p < 0.01.

• 

  Figure 2. Time course for chronic E2 exposure-induced changes in blood pressure parameters. Line graphs depicting mean arterial pressure (MAP; mmHg) (A), systolic blood pressure (SBP) (B), diastolic blood pressure (DBP; mmHg) (C) and heart rate (HR; beats/min) (D): closed red circles represent E2 pellet implanted (20 ng/day, 90-day slow-release pellets) and closed black triangles represent control rats (n = 7–8/group). Panels on the right: Bar graphs showing the average values of the cardiovascular parameters over the entire observation period. *Denotes significant difference (p < 0.05) from control rats.

• 

  Figure 3. Effect of chronic E2 exposure on the gene expression of ET-1 and its receptors in the RVLM and PVN. The mRNA expression levels of ET-1, ETA and ETB receptor and Angiotensin II type 1 receptor in the RVLM and PVN of control and E2 treated rats are shown in (A–H). The fold change was calculated relative to β-actin by the comparative Ct method using 2−ΔΔCt. The Ct values of all the groups were normalized to control rats (n = 4–5 per group). *Denotes significant difference (p < 0.05) from control group.

• 

  Figure 4. Effect of chronic E2 exposure on protein levels of ETA in the PVN. Sample blots and densitometry results from western blot analysis of ETA in the PVN of control and E2-treated rats are shown. Bar graphs represent mean ± SE for 4–5 animals. *Indicates significant difference from control animals.

• 

  Figure 5. Effect of ICV ETA antagonist on chronic E2-induced increase in MAP. (A–D): Line graphs depicting MAP (mmHg), systolic blood pressure (SBP), diastolic blood pressure (DBP; mmHg) and heart rate (HR; beats/min) respectively: closed circles in red represent E2 pellet implanted (20 ng/day, 90-day slow-release pellets) treated with aCSF (E2 + aCSF) and closed triangles represent control SD rats treated with aCSF (C + aCSF), Blue squares represent control rats treated with ETA antagonist (BQ-123) (C + BQ-123) and closed circles in black represent E2 pellet implanted (20 ng/day, 90-day slow-release pellets) rats treated with BQ-123 (E2 + BQ-123). Inverted arrow indicates the day ETA receptor antagonist (BQ-123) administered i.c.v.