Apparently, the mesenchymal cells differed with respect to Ang II receptor expression, since cells within the same area showed marked differences in Ang II binding (Fig. 9).
The 125I-[Sar1-Ile5-Ile8]-Ang II binding in the allantoam-nionic membrane was always relatively weak (data not shown). It occurred mainly in the mesenchyme in close relation to the allantoic endoderm and amnionic ectoderm, and around the few arteries. The predominant Ang II receptor type was the AT2 receptor. The allantoic endoderm and amnionic ectoderm did not reveal any binding.
Displacement studies using both losartan and PD 123319 revealed non-AT1/non-AT2 Ang II binding sites mainly located in the placentome, namely in the lamina propria of the endometrium and on the lower-order septa of the maternal crypts. In all fetal compartments, only slight binding was observed. In three out of five allantochorionic inter-cotyledonary membranes and in three out of three allan-toamnionic membranes, most of the non-AT1/non-AT2 Ang II binding sites were located in the mesenchymal tissue. buy ortho tri-cyclen online
No difference in the pattern of distribution of Ang II receptors was observed throughout gestation.
FIG. 8. Brightfield photomicrograph combined with epipolarised light showing a detail of emulsion-dipped cryosection of a bovine placentome (Day 235). Bright grains indicate the presence of 125I-[Sar1-Ile5-Ile8]-Ang II-labeled receptors. F, Fetal villus; M, maternal crypt; solid arrows, tro-phoblast cells covering the fetal villi; open arrows, uterine epithelium covering the maternal crypt; white asterisks, binucleate (migrating) cells. Bar = 75 ^m.
FIG. 9. Detail of a bovine placentome (Day 235). Brightfield photomicrograph of a hematoxylin and eosin-stained, emulsion-dipped section showing 125I-[Sar1-Ile5-Ile8]-Ang II binding to AT2 receptors of fetal mesenchymal cells in the presence of losartan. Black silver grains indicate presence of labeled receptors. Bar = 35 ^m.