Placental accumulation of 57Co-vitamin B12 in mice studied by light- and electron-microscopic autoradiography.
Pregnant C57BL mice on day 18 of gestation were injected with 0.114 micrograms cyanocobalamin-57Co and killed either 40 min or 3 h later. Radioactivity measurements showed that the placenta was the organ with the highest concentration. Light- and electron-microscopic autoradiography of the placental labyrinth showed heavy accumulation of radioactivity in the second (middle) trophoblastic cell layer in the barriers between the maternal and fetal circulations. Silver grains were mainly associated with the folded plasma membrane deep in the cytoplasm or with vesicles, indicating a cellular uptake by pinocytosis. The cytosolic accumulations present may be derived from cellular metabolic sites, such as that of protein synthesis.
D000818:Animals; D001345:Autoradiography; D003037:Cobalt Radioisotopes; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D014327:Trophoblasts / Q000378:metabolism; D014805:Vitamin B 12 / Q000378:metabolism*
D003037:Cobalt Radioisotopes; D014805:Vitamin B 12