THE FATE OF INGESTED GLYCERAN ESTERS OF CONDENSED CASTOR-OIL FATTY-ACIDS [POLYGLYCEROL POLYRICINOLEATE (PGPR)] IN THE RAT

Samples of the emulsifier polyglycerol polyricinoleate (PGPR) were syn thesized using the radiolabelled precursors [1-C-14]glycerol ([C-14]po lyglycerol PGPR), [9,10-H-3] or [12-H-3]ricinoleic acid ([H-3] PGPR) o r [1-C-14]stearic acid ([C-14]stearyl PGPR). The absorption, tissue di stribution, metabolism and excretion of these C-14- Or tritium-labelle d PGPR samples administered to rats was studied. The effects of intest inal and porcine pancreatic lipases on PGPR preparations were examined . Rats were dosed with [1-C-14]glycerol, [C-14]polyglycerol and ([C-14 ]polyglycerol)PGPR by gavage and their urine, faeces and expired CO2 m onitored for C-14. The results from the [1-C-14]glycerol treated anima ls showed extensive metabolism of glycerol. For [C-14]polyglycerols, t he lower polyglycerols were preferentially absorbed from the intestine and were excreted unchanged in the urine while the higher polyglycero ls were found in the faeces. After 4 days, 93% of the dose of polyglyc erols was recovered, of which some 30% was found in the urine and 60% in the faeces. Traces of C-14 activity were found in depot Fat and liv er. The excretory pattern and urinary metabolites from ([C-14]polyglyc erol) PGPR was very similar to that of [C-14]polyglycerol. Analysis of urinary and faecal C-14 material indicated that the PGPR polymer was digested to give free polyglycerol and polyricinoleic acid. PGPR was s ynthesised incorporating [1-C-14]stearic into polyricinoleic acid whic h was then esterified with polyglycerol. The resulting [C-14]PGPR or [ 1-C-14] stearic acid in a dietary slurry was administered to groups of fed or starved rats by gavage. The results indicated complete digesti on Of PGPR and absorption of the fatty acids. The C-14-material absorb ed was extensively laid down in depot fat and some metabolism to (CO2) -C-14 was demonstrated. The fate of the stearic acid was similar wheth er dosed alone or incorporated into the PGPR polymer. Samples of PGPR were synthesized containing H-3-labelled ricinoleic acid. The resultin g [H-3]PGPR was intubated into rats as a component of a dietary slurry . The results indicated that the polymer is extensively digested and 9 0% of the administered tritium is absorbed. The absorbed material was extensively metabolized within 24 hr so that large amounts of tritium were present in the aqueous phase of the tissues examined. After 24 hr , less than 5% of the administered material was present as lipid mater ial, of which a large proportion was as non-hydroxy fatty acids. No tr aces of polymer material were found in the tissues examined. In vitro digestion of PGPR by porcine pancreatic lipase and rat intestinal frac tions was demonstrated. The results indicate very extensive digestion of the PGPR polymer to polyglycerols and fatty acids. The fatty acids are metabolized extensively. The mono-, di- and triglycerols are exten sively absorbed from the intestinal tract and rapidly excreted in the urine unchanged but the hexa-, penta- and higher polyglycerols are ess entially not absorbed and excreted in the faeces unchanged. (C) 1998 P ublished by Elsevier Science Ltd. All rights reserved.