AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 2 246-G252, Copyright © 1987 by American Physiological Society
Effect of luminal or circulating nitrite on colonic ion movement in the rat
B. C. Radcliffe, S. H. Nance, E. J. Deakin and W. E. Roediger
The disposition of intravenously or luminally administered nitrite across
the colonic mucosa and its effect on ion movement into or from the colon
was assessed in anesthetized Porton rats using the isolated colon instilled
either with sodium chloride (120 mM) or sodium chloride (80 mM) with sodium
butyrate (40 mM). Ionic changes in the colon after intravenous injection of
10 mumol NaNO2 were compared with those occurring after injection of 10
mumol NaCl. After intravenous administration of nitrite, both nitrite and
nitrate appeared in the colonic instillate in a ratio of 1:1. Nitrite
increased chloride absorption (110%) and bicarbonate production (20%) when
40 mM butyrate was included in the instillate. Net sodium absorption,
measured in the whole colon, was unchanged. Intravenous nitrite had no
effect on ionic movement in the absence of butyrate. When NaNO2 (100
microM) was included luminally with the sodium chloride-butyrate
instillate, bicarbonate production rate increased (25%), but sodium and
chloride absorption were unaffected. Nitrite concentration in the
instillate decreased during the 40-min experimental period at a rate of
0.275 nmol X min-1 X cm-2, and nitrate appeared at a rate of 0.037 nmol X
min-1 X cm-2. We conclude that nitrate stimulates bicarbonate production in
the colon, probably by stimulating the oxidation of butyrate, the main
source of CO2 generation by the colonic mucosa.
