Estrogens Regulate Angiotensin-Converting Enzyme and Angiotensin Receptors in Female Rat Anterior Pituitary

Abstract

We studied the effects of the estrous cycle, ovariectomy and estrogen replacement on angiotensin-converting enzyme (ACE) (kininase II, EC 3.4.15.1) and angiotensin II (AT) receptors in the pituitary gland of the female rat. Quantitative autoradiography, with the use of consecutive pituitary sections, allowed for simultaneous determination of changes in binding and in the potential AT synthetic ability of individual pituitaries, and for a correlation between these two phenomena. In the anterior pituitary, ACE activity and binding of the ACE inhibitor [¹²⁵I]-351A were not changed during the estrous cycle. Ovariectomy produced a significant increase in ACE activity and binding, and both of these parameters returned to normal after estrogen replacement. There were no changes in ACE activity or binding in the posterior pituitary during the estrous cycle or after ovariectomy or hormone replacement. AT receptors were characterized as of the AT₁ type, since they were displaced by the selective AT₁ antagonist DuP 753 and not by the AT₂ competitor PD 123177. There were marked changes in the concentration of AT₁ receptors during the estrous cycle, with highest numbers in metestrus, lower in estrus and diestrus, and lowest during proestrus. Estrogen replacement in ovariectomized rats decreased AT₁ receptor number in the anterior pituitary. Our results indicate a dual effect of estrogen on anterior pituitary AT, physiologically on AT receptor expression and pharmacologically on ACE activity.

Angiotensin II AT1AReceptor mRNA Expression Is Induced by Estrogen–Progesterone in Dopaminergic Neurons of the Female Rat Arcuate Nucleus

“…Estrogen treatment of OVX rats downregulates the number of AT 1 receptors in the anterior pituitary (Chen and Printz, 1983;Carriére et al, 1986;Seltzer et al, 1992). Our present results indicate that a combined estrogen and progesterone treatment of OVX rats also results in a downregulation of AT 1 receptors in the anterior pituitary.…”

“…In the first group each rat received one pellet of 17␤-estradiol (0.05 mg /pellet) at 10:00 A.M. (Day 0) placed subcutaneously in the interscapular region. This replacement dose of estrogen (0.05 mg / pellet) has been shown to result in 17␤-estradiol levels of Ͻ50 pg /ml (Seltzer et al, 1992). In the second group each rat received one placebo pellet (Innovative Research of America).…”

“…Treatment of estrogen-primed ovariectomized (OVX) rats with progesterone upregulates Ang II receptors in selective brain areas involved in the inhibition of pituitary prolactin release, whereas estrogen treatment downregulates the expression of Ang II receptors in the anterior pituitary (Chen and Printz, 1983;C arriére et al, 1986;Seltzer et al, 1992Seltzer et al, , 1993.…”

Estrogen modulation of baroreflex function in conscious mice

“…However, it has been shown that in ovariectomized rats estrogen replacement decreases AT 1 receptor expression and binding affinity at several central sites including the subfornical organ, a circumventricular organ (24,25,40,44). In mice, it is interesting to hypothesize that ANG II receptor (AT 1 ) expression at central nuclei mediating the effects of ANG II on baroreflex function could be greater in males compared with OvxEϩ females.…”

Glucocorticoid and mineralocorticoid regulation of angiotensin II type 1 receptor binding and inositol triphosphate formation in WB cells

“…Total RNA from WB cells and adult Sprague-Dawley rats (Harlan, Indianapolis, IN, USA) anterior pituitary (Seltzer et al 1992) was extracted using Trizol reagent (Life Technologies) according to the manufacturer's instructions. Ten micrograms total RNA were reversetranscribed using M-MuLV reverse transcriptase (Pharmacia Biotech, Piscataway, NJ, USA) and 0·2 µg random primed hexamers for 37 C for 1 h. The PCR reaction was carried out in 50 µl volume with 5 µl 10 PCR buffer II (Perkin Elmer, Foster City, CA, USA), 3 µl 25 mM MgCl 2 , 4 µl 2·5 mM dNTPs, 1 µl cDNA template, 50 ng each MR primer, and 2·5 U AmpliTaq-DNA Polymerase (Perkin Elmer).…”