AJP - Gastrointestinal and Liver Physiology, Vol 257, Issue 5 760-G765, Copyright © 1989 by American Physiological Society
Vitamin D3 and glucose-6-phosphate dehydrogenase in rat duodenal epithelial cells
L. B. Nasr, J. D. Monet, P. Lucas and C. A. Bader
Institut National de la Sante et de la Recherche Medicale, Hopital Necker, Paris, France.
A microdensitometric method was employed to determine enzyme activities in
situ in undisrupted tissue rat duodenum. The effect of 1
alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] on glucose-6-phosphate
dehydrogenase (G6PD) activity and on the two utilization pathways of
synthesized NADPH, H1 (mixed function oxidation) and H2 (biosynthesis), was
studied. In normal animals, a crypt-to-villus gradient of G6PD activity and
of both NADPH utilization pathways was observed. A high level of NADPH
utilization occurred predominantly via the H2 pathway. In vitamin
D-deficient rat animals, G6PD activity in the middle part of the villus was
approximately 60% lower than in normal animals [10.05 +/- 0.35 vs. 3.95 +/-
0.26 (means +/- SE) A585.min-1.micron-3 X 10(5), P less than 0.001] with
reduced NADPH utilization via the H2 pathway (8.39 +/- 0.49 vs. 2.73 +/-
0.43 A585.min-1.micron-3 X 10(5), P less than 0.001) but not the H1 pathway
(1.65 +/- 0.17 vs. 1.22 +/- 0.19 A585.min-1.micron-3 X 10(5), P = NS).
Intraperitoneal administration of 1,25(OH)2D3 (500 pmol) to vitamin
D-deficient animals resulted in increased G6PD activity within 30 min (4.09
+/- 0.38 vs. 5.51 +/- 0.39 A585.min-1.micron-3 X 10(5), P less than 0.05),
attaining normal levels within 2 h. The H2 but not the H1 pathway of NADPH
utilization increased significantly in response to 1,25(OH)2D3. This
increase is essentially located in the basal and middle parts of the
villus. Thus 1,25(OH)2D3 may influence biosynthesis in the duodenum via
stimulation of G6PD activity and the H2 pathway of NADPH utilization.
