Abstract
Background: The aim of this work was to study the serum bioavailability of glucose and alanine after bolus injection into the peritoneal cavity in Wistar rats and to determine the influence of their metabolism on the rate of absorption of these nutrients. Methods: A group of animals (n = 14) was infused intraperitoneally (IP) or IV with 2 μCi of nonmetabolizable L-[1-14C]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 μCi of nonmetabolizable D-[U- 14C]alanine diluted in 2 mL of an iso-osmolar L-amino acid solution/250 g body wt, after which both plasma radioactivity and L-alanine concentration were determined. The constants of absorption from peritoneal cavity (K
a) and elimination from plasma (K
e) and the serum absolute bioavailability BA
a) after 8 h were calculated assuming a bicompartment pharmacokinetic model. Results: L-glucose: K
a = 3.05 ± 0.97 h-1; K
e = 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
a = 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 glycosuria appeared in any case. Conclusions: The absorption rate from peritoneal cavity is nearly 10-fold higher than the elimination rate from plasma for the three substrates. Eight hours after IP injection an abso lute 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 L-alanine is better absorbec then D-alanine. These results show that upon IP injection the stud ied nutrients are almost completely absorbed in a short period of time without hyperglycemia or neoglucogenesis and so sug gest that their administration may be a feasible approach to feed ing patients receiving peritoneal dialysis. This model could be applied to other compounds, such as peptides and disaccharides (Journal of Parenteral and Enteral Nutrition
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