Cyclic adenosine-3',5'-monophosphate and folate transport in rat jejunum.

The intestinal transport of 5-methyltetrahydrofolate and pteroylmonoglutamate was examined in everted sacs of rat jejunum exposed to compounds which increase intracellular cyclic adenosine-3', 5'-monophosphate. Adenyl cyclase stimulators (hydrocortisone and prostaglandin), phosphodiesterase inhibitors (3-isobutyl-l-methylxanthine, aminophylline and papaverine), and dibutyryl adenosine-3',5'-cyclicmonophosphate added to the mucosal medium inhibit the mucosal-to-serosal transport of physiological concentrations of 5-methyltetrahydrofalate and pteroylmonoglutamate. Transport inhibition is correlated with the ability of these agents to increase cellular cyclic adenosine-3', 5'-monophosphate. The active, carrier-mediated transport system of folate compounds is highly sensitive to the increase in cyclic adenosine-3', 5'-monophosphate level, while the diffusion system is insensitive. These data indicate that the active transport system of folates is modulated by cellular cyclic adenosine-3', 5'-monophosphate.