Endothelin in rabbit uterus during pregnancy.
Specific immunostaining for endothelin-1 (ET-1) was observed in the uterine mucosa of pregnant and nonpregnant rabbits. During gestation, giant cells immunopositive for ET-1 were identified in either endometrium or myometrium. In the latter, they were located in close proximity to the muscular fibers. High-affinity (dissociation constant = 0.25 nM) high-capacity [maximal binding (Bmax) = 7 pmol/mg protein] receptors for ET-1 were present in myometrial membranes of estrous rabbits. During pregnancy the concentration of ET-1 receptors progressively decreased (Bmax on day 29 = 4 pmol/mg protein), rising again at the time of spontaneous delivery. Conversely, ET-1 receptors in the aorta did not change during pregnancy and parturition. The presence of giant cells immunopositive for ET-1 in close proximity to the myometrial cells, together with the evidence of an increase in ET-1 receptors in myometrium of parturient rabbits, suggests a paracrine role for endometrial ET-1 during delivery. Because we previously demonstrated that oxytocin releases ET-1 from endometrial cells in primary culture and that endometrial and myometrial oxytocin receptors abruptly rise at the time of parturition, we propose that ET-1 might participate in the complex cell-to-cell interactions that occur during labor.
Peri
A
A
Department of Human Anatomy and Histology, University of Florence, Italy.
Vannelli
G B
GB
Fantoni
G
G
Giannini
S
S
Barni
T
T
Orlando
C
C
Serio
M
M
Maggi
M
M
D000818:Animals; D001667:Binding, Competitive; D002851:Chromatography, High Pressure Liquid; D016232:Endothelins / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism; D017466:Receptors, Endothelin; D013997:Time Factors; D014599:Uterus / Q000378:metabolism*
D016232:Endothelins; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin