[Identification of angiotensin II receptor and determination of its subtypes in rabbit and guinea pig fetal tissue].
Membrane angiotensin II receptors were measured in trophoblastic tissues using a 2-step procedure. The first step consisted of the relative measurement performed at a fixed 125I[Sar1 Ile8]AII concentration of 0.15 nM in order to determine which tissues had a sufficient number of binding sites for studying the competition curves. The second consisted of determining the maximal binding (Bmax) and the dissociation constant (Kd) for [Sar1 Ile8] AII and the receptor subtypes in these tissues. The relative binding measurement revealed a significant number of occupied sites in rabbit fetal placenta and chorion (159 +/- 17 and 51 +/- 10 fmol/mg proteins) and in guinea pig chorion (132 +/- 12). The mean values of the other trophoblastic tissues were 3-10-fold lower in the 2 species. The competition curves obtained from tissues with high angiotensin II binding receptors showed the predominance of the AT2 subtype in rabbit fetal placenta (AT1/AT2 = 25/75) and of the AT1 receptor in guinea pig chorion (97/3) and in rabbit chorion (90/10). The [SAR1 Ile8] AII affinity (Kd) obtained from Scatchard plot analysis was 1.2 +/- 0.2 nM (n = 5) in fetal placenta and 1.2 (n = 1) in rabbit chorion and 0.5 +/- 0.1 (n = 3) in guinea pig chorion. In these tissues, the respective Bmax values were 1,281 +/- 115 (n = 5), 263 (n = 1) and 1,188 +/- 134 fmol/mg proteins (n = 3). These findings indicate that rabbit fetal placenta and chorion and guinea pig chorion are the most important sites of action for the renin-angiotensin system present in trophoblastic tissues.
Kalenga
M K
MK
Université catholique de Louvain, Département gynécologie, obstrétrique, Bruxelles, Belgium.
de Gasparo
M
M
Whitebread
S
S
Vankrieken
L
L
Thomas
K
K
De Hertogh
R
R
D015059:1-Sarcosine-8-Isoleucine Angiotensin II / Q000378:metabolism; D000650:Amnion / Q000737:chemistry*; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000737:chemistry; D002823:Chorion / Q000737:chemistry*; D005260:Female; D006168:Guinea Pigs; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D011817:Rabbits; D011945:Receptors, Angiotensin / Q000032:analysis* / Q000378:metabolism; D014327:Trophoblasts / Q000737:chemistry
D011945:Receptors, Angiotensin; D015059:1-Sarcosine-8-Isoleucine Angiotensin II
Identification du récepteur à l'angiotensine II et détermination de ses sous-types dans les annexes foetales du lapin et du cobaye.