Effect of ovariectomy on renal estrogen receptor-alpha and estrogen receptor-beta in young salt-sensitive and -resistant rats.

This study evaluated the effect of ovariectomy on renal estrogen receptor (ER)-alpha and ERbeta expression in young female Dahl salt-sensitive and salt-resistant rats. Our hypothesis was that estrogen depletion results in an imbalance in ERalpha and ERbeta expression in salt-sensitive rats. Rats were subjected to sham surgery (intact), ovariectomy, and ovariectomy with estrogen replacement. Kidneys were harvested 8 weeks later. Western blot was used to measure ERalpha and ERbeta expression in the cortex and medulla. In intact rats, ERalpha was 2.7- and 4.3-fold higher in salt-sensitive compared with salt-resistant rats in the renal cortex and medulla, respectively. In salt-sensitive rats, ovariectomy caused 42% and 52% decreases in ERalpha and 107% and 314% increases in ERbeta in renal cortex and medulla, respectively. In salt-resistant rats, ovariectomy caused 33% and 150% increases in ERalpha and 107% and 100% increases in ERbeta in renal cortex and medulla, respectively. Estrogen replacement did not alter ERalpha but restored ERbeta expression levels similar to levels in intact rats in both salt-sensitive and salt-resistant rats. Thus, estrogen loss had opposite effects on ERalpha in salt-sensitive (downregulation) and salt-resistant rats (upregulation). We propose that the decrease in ERalpha expression in salt-sensitive rats after estrogen loss alters the balance of renal ERs and may play a role in accelerating the development of hypertension and renal damage.