title: Differentiation-dependent expression of calcitriol actions on absorptive processes in cultured chick intestine: modulation by triiodothyronine.
abstract: Embryonic chick jejunum maintained in organ-culture exhibits a characteristic stage-specific pattern of responses to calcitriol and T3. Whereas induction of luminal Na+/inorganic phosphate and Na+/D-glucose transport by calcitriol was only possible at an advanced state of differentiation prior to hatching on day 20, the sterol induced cellular calcium transport with high efficiency even in undifferentiated enterocytes in day 15 embryonic intestine. T3 had no effect at all on calcium transport, but induced Na+/inorganic phosphate transport at all stages of epithelial maturation. In contrast, Na+/D-glucose transport was effectively induced by T3 only in relatively immature intestinal epithelium. T3, at a medium concentration of 10(-8) mol/l, in a permissive fashion potentiated the effects of calcitriol (10(-10)-10(-7) mol/l) on calcium transport as well as on Na+/inorganic phosphate and Na+/D-glucose transfer. Thereby, T3 facilitated induction of transport activities by calcitriol against differentiation-related restraints. By facilitating the expression of genomic actions of calcitriol, T3 may thus play an important role in the regulation of calcium and phosphate metabolism.
authors.affiliation: Department of General and Experimental Pathology, University of Vienna Medical School, Austria.
authors.forename: H S
authors.initials: HS
authors.lastname: Cross
authors.forename: M
authors.initials: M
authors.lastname: Peterlik
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation; D002642:Chick Embryo; D004357:Drug Synergism; D005947:Glucose / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects*; D007583:Jejunum / Q000187:drug effects / Q000196:embryology; D008757:Methylglucosides / Q000378:metabolism; D009924:Organ Culture Techniques; D010710:Phosphates / Q000378:metabolism; D013997:Time Factors; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D008757:Methylglucosides; D010710:Phosphates; D014284:Triiodothyronine; C027020:methylglucoside; D002117:Calcitriol; D005947:Glucose; D002118:Calcium