Transfer kinetics of 3,5,3'-triiodothyronine and thyroxine from rat blood to large and small intestines, liver, and kidneys in vivo

Endocrinology
J J DiStefanoY M Yen

Abstract

Enterohepatic circulation of thyroid hormone in the rat involves transfer of hormone to intestines in bile from the liver and absorption of some intestinal hormone, via portal blood to liver. Transfer of hormone to intestines from mesenteric arterial blood has generally been considered minimal, although this alternate pathway has received little attention. We have measured uptake kinetics of iv trace doses of radioactivity labeled T3 (T3*) and T4* from blood to intestines, longitudinally in 14 segments of total intestines in situ, with bowel contents included and bile duct ligated, and also to liver and kidneys, for comparison. Both T3* and T4* entered the entire length of intestines from blood, and into contents as well as tissue. Tissue uptake of T3* and T4* were fairly uniform longitudinally, but uptake into contents and thus into total intestines (tissue + contents) decreased linearly from pylorus to anus. Unidirectional uptake rate constants (hours-1) or clearance rates (milliliters per h) of T3* were 13 times greater than corresponding T4* fractional uptake rates to intestines. In contrast, T4 mass fluxes (congruent to 38 ng/h.100 g body wt) exceed T3 fluxes (congruent to 6.3 ng/h.100 g body wt) about 6-fold, because plas...Continue Reading

Citations

Jun 14, 2008·Molecular and Cellular Endocrinology·Samantha J Richardson
Sep 4, 2009·The FEBS Journal·Samantha J Richardson
Oct 10, 2006·European Journal of Pharmacology·Yan CaiLiang-zhen Zhou
Jan 8, 2008·Toxicological Sciences : an Official Journal of the Society of Toxicology·Eva D McLanahanJeffrey W Fisher
Aug 30, 2007·The Journal of Clinical Endocrinology and Metabolism·Johanna LaukkarinenIsto Nordback
Aug 4, 1998·The Journal of Nutrition·J L BeardM H Green
Mar 20, 2003·American Journal of Physiology. Endocrinology and Metabolism·Thuvan T NguyenJoseph J DiStefano
Jan 15, 2005·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Samantha J RichardsonMarilyn B Renfree
Jan 30, 2021·European Thyroid Journal·Giulia Masetti, Marian Ludgate

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