137 IRON TRANSFER ACROSS THE LLAMA PLACENTA (LAMA GUANICOE GLAMA)

Abstract

The placenta of the llama has been described as epitheliochorial in type, but recent studies have not shown extensively the fetal nutrition aspects in this animal. In epitheliochorial placentation there is development of structures called areolae, as well as inter-microvillous attachment of the trophoblast, with irregular contact, to the uterine epithelium. This attachment is interrupted and the transfer of substances between the mother and the fetus takes place across the areolar cavity. These areolae appeared as small rounded or dome-shaped elevated areas of the chorioallantoic membrane over the narrow uterine gland openings. In order to detail their mechanisms of iron transfer in the llama placenta, we collected the samples of nine uteri between 28 to 36 weeks of pregnancy in association with fetal membranes. These samples were fixed in 4% paraformaldehyde in PBS, processed, and stained for light microscopy (HE, picrosirius, and Masson's trichrome), histochemistry (Perls, acid phosphatase, and PAS reactions) and immunohistochemistry with rabbit anti pig uteroferrin antibody to confirm the iron transfer, because the uteroferrin is an iron transporter and a progesterone-induced hematopoietic growth factor. The trophoblast formed a columnar-type single layer that was comprised of cells of various sizes and shapes with basal nuclei, including the giant binucleate cells. The trophoblast formed chorionic projections which presented ramifications in number from 4 to 5. A great quantity of blood vessels were found in the materno-fetal interface, between the cells of uterine epithelium and around of the chorionic projections. A PAS-positive reaction was observed with diffuse cytoplasmic PAS staining at the apical region of the trophoblast at the materno-fetal interface as well as in the endometrial glands. Collagen fibers were observed in the mesenchyme and inside the chorionic projections. In the areolae we confirmed the positive reaction of the acid phosphatase enzyme that detects phagocytic activity. In the basal region of the uterine gland epithelium, which is columnar type, and in the gland lumina, this reaction demonstrated a strong positive stain. The Perls histochemical reaction that reveals ferric iron was positive in the areola, as well as in the uterine glands. The uteroferrin immunohistochemistry showed a strong stained in the areolae and in the epithelium and lumina of the uterine glands. Our findings suggest that the areola region and the endometrial glands play an important role in histiotrophic nutrition in llamas, and in fetal red blood cell formation by iron transfer from mother to the fetus.

This work was supported by FAPESP, CNPq, CAPES, PRONEX, Brazil.