EFFECTS OF LUMINAL STIMULI ON POLYAMINE METABOLISM IN THE SMALL-INTESTINE OF THE RAT - THE ROLE OF ENTERIC NERVES

The aim of this study was to investigate to what extent polyamine meta bolism in the small intestine of the rat is controlled by the enteric nervous system. Polyamine metabolism was followed by measuring the act ivity of ornithine decarboxylase (ODC) and in some instances also the content of polyamines (putrescine, spermidine and spermine). ODC activ ity in the intestine was increased when intraluminal pressure was incr eased and 3 h after placing cholera toxin in the intestinal lumen. Cho lera toxin also increased the tissue putrescine content. Atropine or h examethonium given i.v. did not influence the evoked changes of ODC ac tivity. The pressure induced changes were not decreased by placing lid ocaine on the serosal surface. On the other hand, the ODC activity of control segments were decreased by hexamethonium or atropine. The pres ence of glucose in the intestinal perfusate did not augment tissue ODC activity, neither did the heat stable enterotoxin from Escherichia co li (STa). It is concluded that the effect on polyamine metabolism evok ed by luminal pressure or cholera toxin seems not to be mediated via n erves, while nerves seem to influence ODC activity during control cond itions. The experiments with enterotoxins suggest that cAMP is the int racellular second messenger controlling intestinal ODC activity.