Immunohistochemical Identification of Calcium Transporters in the Placenta of Alpacas (Vicugna pacos)

The placenta plays an essential role in calcium transport and regulation during gestation; however, few studies have investigated the identification of placental transporters in animals. The present study aimed to identify calcium transporters in the placentas of postpartum alpacas. A total of 12 placentas were collected from adult huacaya alpacas. The mate- rial was fixed with a 10% formaldehyde solution and reduced in paraffin blocks. The material was fixed with a 10% formaldehyde solution and reduced in paraffin blocks. Sections measuring 5 μm were subjected to hematoxylin- eosin staining and immunohistochemical reactions to detect calbindin D-9K (CaBP-9K) and calbindin D-28K (CaBP-28K). The results obtained in the present study reveal chorionic projections exhibiting a trophoblast with va- riable cell morphology and multinucleated giant cells in the apical regions of the chorionic projections. In turn, columnar trophoblastic cells with a developed cytoplasm and a centric nucleus were observed. A moderate immunoexpression to CaBP-9K was identified in the chorionic trophoblast cells, being lower towards CaBP-28K, the multinucleated giant cells showed a moderate immunoexpression to both transporters, likewise, CaBP-28K showed a moderate reaction in the columnar cells, being more intense in the apical surface, while CaBP-9K showed a mild immunoexpression, regarding the allantois, this showed a moderate immunoexpression to CaBP- 28K. These results confirm a complex regulation system of placental calcium transport, since CaBP-28K would act as a regulator of calcium entry into trophoblast cells, especially in the tall columnar cells related to areola formation. At the same time, CaBP-9K, being lighter, is detectable in the trophoblast cytoplasm, thus confirming that calbindins mediate calcium transport in the alpaca placenta, this being the first report in the species.