AJP - Gastrointestinal and Liver Physiology, Vol 263, Issue 3 371-G379, Copyright © 1992 by American Physiological Society
Development of Ca2+ homeostasis in epithelial cells from embryonic and neonatal intestine
B. L. Black and J. O. Rogers
Department of Zoology, North Carolina State University, Raleigh.
The fluorescent probe fura-2 was used to assay Ca2+ levels in epithelial
cell suspensions from embryonic and neonatal chick duodenum. Cell
preparations maintained high viability, completely hydrolyzed fura-2/AM to
fura-2, retained 92% of cellular fura-2 within the cytoplasmic compartment,
and gave low autofluorescence values during assay. Fura-2 leakage from
loaded cells occurred at all ages, but could be corrected for in subsequent
calculations of cellular Ca2+. Cytoplasmic Ca2+ concentration was 76-80 nM
in cells from 14- to 16-day embryonic intestine, rose significantly to
92-98 nM at 17-20 days, and reached 209 nM at 1-day post-hatch when assayed
in buffers containing 1.3 mM Ca2+. The developmental rise in cytoplasmic
Ca2+ was accompanied by an enhanced ability of cells to maintain a constant
Ca2+ concentration at increased levels of extracellular Ca2+ and by a
highly correlated rise in alkaline phosphatase (ALP) activity. Epithelial
Ca2+ subsequently decreased to the "adult" value of 133-142 nM and was
constant along the crypt-villus axis of neonatal intestine. These results
verify that fura-2 can be used to compare baseline cytoplasmic Ca2+ values
of epithelial cells from developing intestine, reveal that significant
changes in Ca2+ homeostasis occur during ontogeny, and suggest that
epithelial Ca2+ may modulate ALP activity during the differentiation of
embryonic enterocytes.
