Autoradiographic Localization and Characterization of Angiotensin II Receptors: RESULTS(4)

RESULTS(4)Renin Concentrations

The renin concentrations in bovine placentae and fetal membranes (Table 4) were low or, in several animals, even below the detection limit (0.014 GU/kg wet tissue weight). In the intercotyledonary membrane and the allantoamnionic membrane, no renin could be detected during the first part of gestation. All measured renin was completely inhibited by the specific renin inhibitor remikiren, indicating that no nonrenin enzymes, capable of forming Ang I, were present in the placenta and fetal membranes. buy ampicillin

Autoradiography

In the intercotyledonary allantochorionic membrane, most of the 125I-[Sar1-Ile5-Ile8]-Ang II binding occurred in the mesenchymal tissue. It was localized to mesenchymal cells adjacent to the trophoblast cell layer and around the larger and smaller arteries, and, with less intense staining, in close relationship to the allantoic endoderm (Fig. 4). In accordance with the Ang II receptor binding study, the predominant Ang II receptor type was the AT2 receptor (Fig. 4a). The less pronounced AT receptor binding appeared in the same localizations as the AT2 receptors (Fig. 4b). The allantoic endoderm and the trophoblast cells did not bind 125I-[Sar1-Ile5-Ile8]-Ang II. The uterine epithelium did not bind 125I-[Sar1-Ile5-Ile8]-Ang II, whereas the lamina propria of the endometrium mainly revealed AT1 receptor binding (Fig. 4b), less AT2 receptor binding (Fig. 4a), and only scarce non-AT1/non-AT2 Ang II binding sites (Figs. 4e and 5b).
Fig4Autoradiographic Localization
FIG. 4. Autoradiograms showing the distribution of 125I-[Sar1-Ile5-Ile8]-Ang II binding in serial cryosections of a smooth part of the bovine placenta (Day 145). Dark regions indicate high density of labeled receptors. a) Binding in the presence of lo-sartan showing AT2 receptor binding. b) Binding in the presence of PD 1 2331 9 showing AT1 receptor binding. c) Total binding. d) Binding in the presence of 1 ^M unlabeled [Sar1-Ile5-Ile8]-Ang II. e) Binding in the presence of both PD 12331 9 and losartan. *, Artery; MES, fetal (somatopleural) mesenchyme; arrowhead, trophoblast layer; open arrow, uterine epithelium; LP, lamina propria of the endometrium. Bar = 150 ^m.

Fig5Autoradiographic Localization
FIG. 5. Autoradiograms showing the distribution of 125I-[Sar1-Ile5-Ile8]-Ang II binding in serial cryosections of a smooth part of the bovine placenta (Day 115). Black silver grains indicate presence of labeled receptors. a) Total binding. b) Binding in the presence of both PD 123319 and losartan. c) Binding in the presence of 1 ^M unlabeled [Sar1-Ile5-Ile8]-Ang II. MES, Fetal mesenchyme; solid arrows, trophoblast layer; open arrows, uterine epithelium; LP, lamina propria of the endometrium. Bar = 60 ^m.

TABLE 4. Active renin concentration (GU X 10~3/kg wet tissue) in the bovine placenta and fetal membranes, given as median with range in parentheses.*

Day 1-95 Day 96-190 Day 191-290
Placentome 23 (15-56; n = 3) 31 (15-48; n = 4) 38 (n = 1)
bd (n = 4) bd (n = 5) bd (n = 6)
Intercotyledonary membrane bd (n = 7) 23 (14-33; n = 5) 3 7 (1 9-56; n = 3)
bd (n = 4) bd (n = 4)
Allantoamnionic membrane bd (n = 7) 39 (3 7-70; n = 3) 26 (14-38; n = 2)
bd (n = 6) bd (n = 5)

* bd, below the detection limit (< 14 X 10~3/kg wet tissue weight); n, number of animals.

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