Effect of dehydroepiandrosterone on pentose phosphate pathway activity in the rat colon

1. The effects of fasting and fasting followed by refeeding on the activities of the oxidative pentose pathway (OPP) and the non-oxidative pentose pathway (NOPP) were estimated by the rate of production of 14CO2 from [1-14C] glucose in isolated rat colonocytes, and the production of hexose 6-phosphates from ribose 5-phosphate in rat colonic cytosols, respectively. 2. The OPP activity in colonocytes from rats in the fasted state was 50% lower when compared to colonocytes from rats refed after a fast. This indicated induction of the rate-limiting enzyme of the OPP, glucose 6-P dehydrogenase (G6-PDH) in the latter instance. No effect on the maximal catalytic activity of the enzymes of the NOPP was seen in colonocytes from rats refed after a fast compared with colonocytes from rats in the fasted state. 3. Isolated colonocytes obtained from the distal colon of rats refed after a fast, showed a significant decrease (30%) in OPP activity when incubated with 50 microM dehydroepiandrosterone (DHEA). A similar degree of inhibition was seen with 10 mM butyrate (P < 0.05). In contrast, using colonic cytosols, both DHEA and butyrate had no effect on the maximal catalytic activity of the NOPP. 4. Intraperitoneal injection (i.p.) of DHEA in rats refed after a fast showed a significant increase in the maximal catalytic activity of the NOPP in the distal colon (46%; P < 0.05). A similar elevation in the maximal catalytic activity of the NOPP was seen in the distal colon of DHEA treated pair-fed rats (43%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)