Influence of chronic oestrogen treatment on the density of muscarinic cholinergic receptors and calcium channels in the rabbit uterus

Abstract

Ovariectomized rabbits were treated for 1 or 8 weeks with oestrogen and the effects on uterine weight, muscarinic receptor density and nitrendipine-binding sites on myometrial membranes were studied. The wet weight of the uterus after 1 week of oestrogen treatment increased more than tenfold and increased further by approximately 50% after 8 weeks of oestrogen treatment. The muscarinic receptor density increased significantly after 1 week of oestrogen treatment. Although there was no further increase in receptor density with continuing oestrogen treatment up to 8 weeks, the muscarinic receptor affinity increased significantly. The density of nitrendipine-binding sites increased sixfold after 1 week of oestrogen treatment and did not change thereafter. Oestrogen treatment had no influence on the affinity of nitrendipine-binding sites. The increase by oestrogen in muscarinic receptor density and in nitrendipine-binding sites as shown by the present data is consistent with the generally reported increase in agonist-induced contractile response of the myometrium following oestrogen treatment.

Effects of estrogen on nitric oxide synthase and histological composition in the rabbit clitoris and vagina

“…Estrogen treatment of rats and rabbits usually lead to an increase in contractility in the reproductive organs. 24,25 Considering the calcium channel blocking effect of estradiol that is already known, it is assumed that the changes of clitoris and vaginal tissues after oophorectomy and estrogen replacement reported by other authors is not the sole effect of the change in NOS production, but is the ®nal consequence of many other factors affecting in a complex way. 17 ± 19,26 Furthermore, depending on the tissue, there is diversity in the mechanism by which ovarian steroids can in¯uence the smooth muscle function.…”

Recent progress in understanding the non-neuronal cholinergic system in humans

“…Temperature, too, modulates the intensity of ACh synthesis and degradation (Massarelli et al, 1988;Sanchez-Yague et al, 1990) as well as ACh receptor function (Green and Claudio, 1993). Endocrine hormones and growth factors have been shown to alter expression and activity of cholinergic enzymes and receptors (Batra, 1990;Biagioni et al, 2000;Bleisch and Harrelson, 1989;Braun et al, 1993;Tria et al, 1992). Activation of the immune system, for example, T cells via the TCR/CD3 complex-or via CD11a-mediated pathways, enhances synthesis and release of ACh along with specific up-regulation of M 5 muscarinic receptors and acetylcholinesterase expression (Kawashima and Fujii, 2004).…”

Estrogen therapy induces collateral and microvascular remodeling

“…The dose of estradiol used in the present study was sufficient to obtain physiological levels of estradiol for rabbits (1,2,11,18).…”

“…After induction of anesthesia with ketamine and xylazine (35 and 5 mg/kg im, respectively) and then with halothane (0.75-1.5%), the rabbits were mechanically ventilated, and their ovaries were removed using sterile surgical techniques after a midline incision in the abdomen (OVX, n ϭ 11). 17␤-Estradiol was administered once per week (1 mg/kg im) to another group (OVX-ES, n ϭ 12) (1,2,11,18).…”