Intestinal First-Pass Metabolism via Carboxylesterase in Rat Jejunum and Ileum

Abstract

ABSTRACT:To determine the activity of a major intestinal esterase in the first-pass hydrolysis of O-isovaleryl-propranolol (isovaleryl-PL), a model ester compound, rat intestinal jejunum and blood vessels were perfused simultaneously after inhibition of a carboxylesterase (CES) by bis-p-nitrophenyl phosphate (BNPP). BNPP specifically inhibits approximately 90% of CES activity without influencing aminopeptidase activity or the transport of L-leucyl-p-nitroanilide and p-nitroaniline, nonester compounds. When isovaleryl-PL was perfused into the jejunal lumen after BNPP treatment, its absorption clearance (7.60 ؎ 0.74 l/min) increased approximately 3-fold compared with control, whereas its degradation clearance (32.5 ؎ 5.40 l/min) decreased to 23% of control. Therefore, CES seems to be mainly responsible for the intestinal first-pass hydrolysis of isovaleryl-PL. This finding is consistent with the results from studies of in vitro BNPP inhibition in the mucosal S9 fraction. V max values for valeryl-PL, isovaleryl-PL, and p-nitrophenyl acetate in the jejunal S9 fraction were 1.7-to 2.5-fold higher than that in the ileal S9 fraction, which agreed with the jejunum/ileum ratio (approximately 1.5-fold) of mRNA expression levels for the CES2 isozymes, AB010635 and AY034877. These findings indicated that CESs expressed in the intestine markedly contribute to first-pass hydrolysis in both jejunum and ileum.

Prediction of Human Intestinal Absorption of the Prodrug Temocapril by In Situ Single-Pass Perfusion Using Rat Intestine with Modified Hydrolase Activity

“…The perfusates from the luminal segment and vascular outflow were collected at appropriate points. A CES-inhibited condition was achieved by preperfusion with BNPP (400 M) for 40 min, in accordance with a previously reported methodology (Masaki et al, 2007). The chemical degradation of temocapril was negligible during the perfusion experiment.…”

“…Masaki et al (2007) proposed a methodology whereby rat intestinal CES was inhibited by BNPP; BNPP irreversibly inhibits all CES isozymes with K i values of 44.9 Ϯ 4.95 nM in rat jejunal S9 but has no effect on other hydrolases such as aminopeptidase. Masaki et al (2007) also established that nearly complete inhibition of CES is obtained by preperfusion with BNPP (400 M for 40 min). More recently, Ohura et al (2010) reported that BNPP affects neither active transport, e.g., p-glycoprotein, peptide, and organic anion transporters, nor passive diffusion in Caco-2 cell monolayers.…”

“…is rapidly hydrolyzed by rat intestinal CES, human intestinal absorption of temocapril cannot be predicted by rat single-pass perfusion experiments; therefore, this single-pass perfusion experiment was performed under inhibition of CES-mediated hydrolysis using BNPP, according to a previously reported methodology (Masaki et al, 2007). Masaki et al (2007) proposed a methodology whereby rat intestinal CES was inhibited by BNPP; BNPP irreversibly inhibits all CES isozymes with K i values of 44.9 Ϯ 4.95 nM in rat jejunal S9 but has no effect on other hydrolases such as aminopeptidase. Masaki et al (2007) also established that nearly complete inhibition of CES is obtained by preperfusion with BNPP (400 M for 40 min).…”

“…To predict human intestinal absorption in the rat model, we used the previously reported methodology for inhibition of CES-mediated hydrolysis by preperfusion with BNPP (Masaki et al, 2007). The absence of CES-mediated hydrolysis led to an increase in the intramucosal concentration of temocapril, followed by an increase in CL abs and decrease in P eff (Table 3).…”

Increased Systemic Exposure to Rhizoma Coptidis Alkaloids in Lipopolysaccharide-Pretreated Rats Attributable to Enhanced Intestinal Absorption

“…Intestinal cellular S9 fractions were prepared as described previously (Masaki et al, 2007), with modifications. In dmd.aspetjournals.org brief, the small intestines were excised and rinsed with chilled 1.15% KCl.…”