Diet and carcinogen alter luminal butyrate concentration and intracellular pH in colonocytes.
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Butyrate (BUT) is an important colonie anion and metabolite which may significantly influence the intracellular pH (pHi) of colonocytes. Recently, pHi has been shown to be important to tumorigenesis. To investigate the relationship of diet and carcinogen to pHi and production of BUT in the colon we conducted a 2x2 factorial design study. Thirty male Sprague-Dawley rats were fed diets with either poorly fermented cellulose (CELL) or highly fermented pectin (PEC), injected with the colon carcinogen azoxymethane (AOM) or saline (SAL), and euthanized 40 wk post-injection. Feces from proximal (PRO) and distal (DIS) colon were collected for determination of short chain fatty acids by gas chromatography. Colonie crypts were dissociated and placed into short term culture. Basal pH; was determined using BCECF-AM and anchored cell laser cytometry. Results: In both PRO and DIS, [BUT](umol/g feces) was higher (P<0.05) in PEC rats (PRO: 4.50.4=PEC/AOM, 3.40.5=CELL/AOM,4.70.4=PEC/SAL,4.10.4=CELL/SAL;DIS:4. 60.3=PEC/ AOM, 3.50.6=CELL/AOM, 4.80.3=PEC/SAL, 4.00.2=CELL/SAL). Basal pH, of PRO cells was lower than DIS, except in CELL/AOM rats. AOM rats had consistently lower luminal [BUT] than SAL rats, and basal pHi of cells from AOM rats was higher than that of controls. These data show that PEC rats produce higher luminal [BUT], and the [BUT] is highest in the PRO where pHi is lowest Alternatively, AOM reduced [BUT] and increased basal pHi. Whether these changes in pHi are due to the changes in [BUT] or to alterations in the cell from the transformation process remains to be determined.
