The effect of duodenal administration of fatty acids, triolein, liquid paraffin and lecithin on plasma neurotensin-like immunoreactivity (p-NTLI) in the rat.

The effect of intraduodenal administration of various types of lipids on the concentration of p-NTLI has been studied on anesthetized rats. Oleic acid, sodium oleate, triolein, linoleic acid, linolenic acid, arachidonic acid, butyric acid, liquid paraffin, phosphatidyl choline (lecithin) and saline were administered. Oleic acid, triolein, linoleic acid and linolenic acid significantly increased the integrated response of p-NTLI. The maximal concentration of p-NTLI was reached 40 min after administration of oleic acid. However after instillation of triolein, the maximal concentration was reached at 100 min which was significantly later. The results indicate that the response of p-NTLI following administration of fat into the duodenum of rats is a specific event caused by fatty acids rather than by lipophilic substances in general. Of the substances tested 18-carbon fatty acids were the most effective in increasing the concentration of p-NTLI. Shorter- or longer-chain fatty acids were less effective. The degree of unsaturation, i.e. the presence of one or more double bounds is also of importance. Triglycerides seem to be hydrolysed to fatty acids before they may bring about an increase in the concentration of p-NTLI. The charge of lipids seems to be critical since the sodium salt of oleic acid had limited effects. Arachidonic acid did not change the integrated response of p-NTLI indicating that products of cyclooxygenase and lipoxygenase pathways are not involved in the fatty acid induced release of NTLI.