A PHARMACOKINETIC STUDY OF PERITONEAL ABSORPTION OF GLUCOSE AND ALANINE IN RATS - NUTRITIONAL IMPLICATIONS

Background: The aim of this work was to study the serum bioavailabilit y of glucose and alanine after bolus injection into the peritoneal cav ity in Wistar rats and to determine the influence of their metabolism on the rate of absorption of these nutrients. Methods: A group of anim als (n = 14) was infused intraperitoneally (TP) or IV with 2 mu Ci of nonmetabolizable L-[1-C-14]glucose diluted in 5 mL of 5% D-glucose/250 g body wt, after which plasma radioactivity was determined. A second group of animals (n = 14) received, either IP or IV, 3 mu Ci of nonmet abolizable D-[U-C-14]alanine diluted in 2 mt of an iso-osmolar L-amino acid solution/2.50 g body wt, after which both plasma radioactivity a nd L-alanine concentration were determined. The constants of absorptio n from peritoneal cavity (K-a) and elimination from plasma (K-p) and t he serum absolute bioavailability (BA(a)) after 8 h were calculated as suming a bicompartment pharmacokinetic model. Results: L-glucose: K-a = 3.05 +/- 0.97 h(-1); K-c = 0.40 +/- 0.12 h(-1); BA(a) = 94% +/- 4% D -alanine: K-a = 1.08 +/- 0.40 h(-1); K-e = 0.11 +/- 0.06 h(-1); BA(s) = 90% +/- 11%. L-alanine: K-a = 1.75 +/- 0.273 h(-1); K-e = 0.02 +/- 0 .01 h(-1); BA(a) = 99% +/- 1%. No hyperglycemia, hypoglycemia, or glyc osuria appeared in any case. Conclusions: The absorption rate from per itoneal cavity is nearly 10-fold higher than the elimination rate from plasma for the three substrates. Eight hours after IP injection an ab solute bioavailability almost as high as after IV injection (ie, close to 100%) was achieved. The metabolism of the nutrients seems to help the peritoneal absorption, as I;alanine is better absorbed then D-alan ine, These results show that upon IP injection the studied nutrients a re almost completely absorbed in a short period of time without hyperg lycemia or neoglucogenesis and so suggest that their administration ma y be a feasible approach to feeding patients receiving peritoneal dial ysis. This model could be applied to other compounds, such as peptides and disaccharides.