Figure 3.

Immunolocalization of endothelin-1 (ET-1), ET_A, and ET_B in uterine vessels and placental labyrinth from pregnant rats treated with saline vehicle or with 2.5 mg/kg/h N^G-nitro-L-arginine-methyl ester (L-NAME) from gestational day 14 to 21. Immunostaining patterns and intensities were similar between the 2 treatment groups. ET-1 localized to the uterine vascular walls in both the vehicle-treated group (A) and the L-NAME–treated group (C). A negative control (omission of primary antibody) from the vehicle-treated group indicates no binding of the secondary antibody-chromogen complex in the absence of primary antibody (B). Placental ET-1 localized primarily to the membranes of the labyrinth in both groups; a representative photomicrograph from the vehicle-treated group is shown (D). ET_A and ET_B receptors in the uterus (E and F, respectively) were localized in the vascular wall in both vehicle and L-NAME–treated groups. In the placenta, these receptors were distributed along the labyrinthine membranes, with ET_A appearing in patches (G) and ET_B having a more uniform distribution (H). Light methyl green counterstain. Bar = 100 μm (A-C and E-H) and 200 μm (D).