High alpha-amylase activity in the syncytiotrophoblastic cells of first-trimester human placentas.
The syncytiotrophoblastic brush border of the human placenta forms the maternal-fetal interface and is an important determinant of placental function. Electron micrographs of fresh brush border preparations isolated from first-trimester human placentas showed membrane vesicles, open-ended microvilli, and numerous glycogen particles. Analysis of the microvillar membranes for several plasma and intracellular membrane markers showed a high degree of purification, comparable to the results reported for the isolation of microvilli from full-term human placentas. The microvillar preparations from first-trimester placentas, however, also contained the enzymes necessary to synthesize and degrade glycogen. The degradation resulted in the accumulation of maltotriose and maltotetraose, apparently due to the action of a liver-type alpha-amylase. The occurrence of this enzyme and the enzymes for synthesizing glycogen in this brush border fraction is probably associated with the necessity for an extremely active glucose transport and liver-like storage system within the fetal tissue at this fetal-maternal membrane interface.
D005260:Female; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D008871:Microvilli / Q000201:enzymology / Q000648:ultrastructure; D010920:Placenta / Q000201:enzymology* / Q000648:ultrastructure; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D014312:Trisaccharides / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology / Q000201:enzymology / Q000648:ultrastructure; D000516:alpha-Amylases / Q000378:metabolism*
D014312:Trisaccharides; C008317:maltotriose; D006003:Glycogen; D000516:alpha-Amylases; D005947:Glucose