Prostaglandin F2α receptor in the neurohypophysis of hens

Abstract

To elucidate whether the receptor for prostaglandin (PG) F(2alpha), one of PG, exists in the neurohypophysis in hens and whether the binding of receptor changes with relation to oviposition, the PGF(2alpha) binding component in the membrane fraction of the neurohypophysis of laying hens was analyzed by radioligand binding assay using [5,6,8,9,11,12,14,15(n)-(3)H]PGF(2alpha). The binding component had characteristics of a receptor such as binding specificity, high affinity, and limited capacity for PGF(2alpha). Scatchard analysis indicated that the binding site was of a single class. The binding capacity of the receptor was smaller in laying hens than in nonlaying hens, whereas the binding affinity was not significantly different between these hens. When non-laying hens received an i.m. injection of estradiol-17beta or progesterone (0.5 mg/hen), the specific binding of the PGF(2alpha) receptor in the neurohypophysis was decreased. In laying hens, the specific binding decreased and the blood arginine vasotocin (AVT) concentration increased just after oviposition but did not change during a 24-h day in nonlaying hens. An i.v. injection of PGF(2alpha) (2 microg/hen) induced oviposition and caused an increase in the blood AVT concentration with a decrease in the specific binding of PGF(2alpha) receptor. The present study suggests a possibility that PGF(2alpha) may directly cause the AVT release from the neurohypophysis at oviposition time in hens.

Properties of estrogen binding components in the plasma membrane of neurohypophysis in hens and changes in its binding before and after oviposition

“…Accordingly, it seems likely that E 2 acts on the neu-rohypophysis through the membrane estrogen receptor regardless of the nuclear estrogen receptor. Estradiol-17β stimulates the action of prostaglandin F 2α in the neurohypophysis (Takahashi and Kawashima, 2009) and increases the AVT concentration in blood (Takahashi et al, 1994a). These facts imply that an administration of estrogen may induce oviposition theoretically.…”

“…All steps were performed at 4°C. Plasma membrane fractions were prepared as reported earlier (Takahashi and Kawashima, 2009). The neurohypophyses were pooled and homogenized in 15 vol/wt Tris-EDTA buffer [TE; 50 mM Tris (Nacalai Tesque Inc., Kyoto, Japan)-HCl, 2 mM EDTA (Wako Pure Chemical Industries Ltd., Osaka, Japan), pH 7.4] by using a Potter-Elvehjem-type glass polytetrafluoroethylene homogenizer with 10 strokes while cooling in an icewater bath.…”

Calcitonin receptor binding in the hen neurohypophysis before and after oviposition

“…At the time of oviposition, the blood level of AVT is known to increase dramatically (Douglas and Sturkie, 1964;Lin, 1966, 1967;Tanaka et al, 1984;Rice et al, 1985;Shimada et al, 1986;Koike et al, 1988;Takahashi et al, 1994b;Takahashi and Kawashima, 2008). Recently, it was reported that receptors for E 2 (Takahashi and Kawashima, 2009b) and PGF 2α (Takahashi and Kawashima, 2009a) existed in the hen neurohypophysis and these hormones acted on this tissue with relation to oviposition. Not only E 2 (Takahashi et al, 1994a) and PGF 2α (Shimada et al, 1987;Takahashi and Kawashima, 2009a) but also acetylcholine (Sturkie and Lin, 1966;Shimada et al, 1987) and angiotensin-II (Goto et al, 1986a) cause an increase in the blood AVT level in hens.…”

“…Recently, it was reported that receptors for E 2 (Takahashi and Kawashima, 2009b) and PGF 2α (Takahashi and Kawashima, 2009a) existed in the hen neurohypophysis and these hormones acted on this tissue with relation to oviposition. Not only E 2 (Takahashi et al, 1994a) and PGF 2α (Shimada et al, 1987;Takahashi and Kawashima, 2009a) but also acetylcholine (Sturkie and Lin, 1966;Shimada et al, 1987) and angiotensin-II (Goto et al, 1986a) cause an increase in the blood AVT level in hens. The present study may suggest that CT is also one of the factors to cause the AVT release from neurohypophysis at the time of oviposition in hens.…”

Changes in angiotensin II receptor bindings in the hen neurohypophysis before and after oviposition

“…The concentration of AVT has been detected to decrease in the neurohypophysis (Tanaka and Nakajo, 1960;1962) and the dramatic increase in blood (Douglas and Sturkie, 1964;Tanaka et al, 1984;Rice et al, 1985;Shimada et al, 1986;Koike et al, 1988;Takahashi et al, 1994a;Takahashi and Kawashima, 2008) just after oviposition. The blood concentration of AVT has been reported to be increased by estrogen (Takahashi et al, 1994b) and prostaglandin F 2α (PGF 2α ; Takahashi and Kawashima, 2009a). Because receptors for estrogen (Takahashi and Kawashima, 2009b) and PGF 2α (Takahashi and Kawashima, 2009a) exist in the hen neurohypophysis, these hormones are thought to act on this tissue.…”