Electron microscopic cytochemical localization of a basolateral calcium adenosine triphosphatase in vitamin D replete chick enterocytes.
A cytochemical technique for the electron microscopic localization of calcium adenosine triphosphatase (Ca-ATPase) was utilized to localize this enzyme in the enterocytes of rachitic and vitamin D-replete chicks. In animals treated with cholecalciferol (CC, vitamin D3), an electron-dense reaction product was located along the basolateral membranes of the absorptive cells within 72 hr after injection. Similarly, a reaction product was identified in association with the basolateral membranes within 24 hr after injection of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D. A microvillar reaction product was not seen in either of these two groups. Electron-dense reaction products were also seen in association with mitochondria and scattered throughout the cytoplasm of these enterocytes. The Ca-ATPase reaction product was dependent upon the presence of medium calcium and substrate (ATP), was inhibited by vanadate, and was heat labile. In the rachitic animals, a reaction product indicative of Ca-ATPase activity was not seen in association with either the basolateral membranes or the mitochondria. These data appear to indicate that an energy-requiring calcium-activated membrane pump plays a role in the flux of calcium across the enterocytes of the small intestine.
Davis
W L
WL
Department of Anatomy, Baylor College of Dentistry, Baylor University Medical Center, Dallas, TX 75246.
Jones
R G
RG
Farmer
G R
GR
Matthews
J L
JL
Martin
J H
JH
Bridges
G
G
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000097:blood; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002645:Chickens; D002762:Cholecalciferol / Q000494:pharmacology*; D004386:Duodenum / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure*; D006651:Histocytochemistry; D008854:Microscopy, Electron
D002762:Cholecalciferol; D000252:Calcium-Transporting ATPases; D002117:Calcitriol; D002118:Calcium