Transepithelial transit time (TET) of solutes absorbed from rat jejunum

Conference · Sat Mar 01 00:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5325546

Foulkes, E C; McMullen, D M

Following passage of a bolus of /sup 14/C-cycloleucine through the rat jejunum, 1 to 2 min elapse before the peak appearance of /sup 14/C in the portal vein. This delay resembles the TET of almost 1 mi for reabsorbed amino acids (AA) in the rabbit kidney. In contrast, a highly permeant molecule like methanol crosses epithelium with a minimal delay of <20 sec. measured peak TET for Ni = 3 to 4 min. This agrees reasonably well with the value of 5 min calculated on the basis of a 3-compartment catenary model by the equation dS/dt = K - kS, where S = mucosal transport, K = constant rate of uptake from the lumen, and k = first order constant of baso-lateral extrusion = 1/TET; at steady state S = K/k. The model adequately describes renal AA reabsorption (1oc cit). With 20 ..mu..M Ni in the lumen, K = 1.4 nmol/g/min, S = 7 nmol/g; k then = 1.4/7 = 0.2 min/sup -1/, and TET = 1/0.2 = 5 min. Mucosal retention of Zn >Ni, and observed and calculated values of TET fall into the range of 10-15 min. TET for Cd exceeds 20 min, i.e. K must be low and S correspondingly high: over 95% of Cd taken up is indeed retained in S. The simple kinetic model validated for transepithelial solute movement in the kidney is thus applicable to metal absorption in the jejunum. TET, as conveniently determined in terms of K and S, presumably reflects reactions of absorbed metals with epithelial binding sites.

• Research Organization: Univ. of Cincinnati Medical Center, OH
• OSTI ID: 5325546
• Report Number(s): CONF-8604222-; TRN: 86-030475
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:3; Conference: 70. annual meeting of the Federation of American Society for Experimental Biology, St. Louis, MO, USA, 13 Apr 1986
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
LEUCINE
INTESTINAL ABSORPTION
MEMBRANE TRANSPORT
MATHEMATICAL MODELS
CARBON 14 COMPOUNDS
COMPARATIVE EVALUATIONS
EPITHELIUM
RATS
RETENTION
SMALL INTESTINE
ABSORPTION
AMINO ACIDS
ANIMAL TISSUES
ANIMALS
BODY
CARBOXYLIC ACIDS
DIGESTIVE SYSTEM
GASTROINTESTINAL TRACT
INTESTINES
LABELLED COMPOUNDS
MAMMALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
RODENTS
TISSUES
UPTAKE
VERTEBRATES
550501* - Metabolism- Tracer Techniques