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Induction of a thoracolumbar supernumerary rib in rat developmental toxicity studies: A short discussion on the critical window
Author(s) -
Kuwagata Makiko,
Senuma Mika,
Todoroki Mai,
Kumagai Fumiaki,
Kumamoto Takayuki,
Ogawa Tetsuo
Publication year - 2019
Publication title -
congenital anomalies
Language(s) - English
Resource type - Journals
eISSN - 1741-4520
pISSN - 0914-3505
DOI - 10.1111/cga.12320
Subject(s) - supernumerary , toxicity , incidence (geometry) , morning , biology , physiology , developmental toxicity , medicine , endocrinology , zoology , anatomy , fetus , pregnancy , genetics , physics , optics
Thoracolumbar supernumerary ribs (TSRs) are classified as less severe skeletal anomalies in rat developmental toxicity studies, although their incidence is relatively high in rodent studies. To investigate the characteristics of the critical window for chemically‐induced TSR, in this study, rats were administered 5‐fluorocytocine (5‐FC) or sodium salicylate (SAL) at one of three time periods on gestational day (GD) 9, early morning (7:00 am ), midday (12:00 pm to 1:00 pm ), or late afternoon (4:00 pm or 7:00 pm ). The incidence of TSR and other anomalies were assessed in GD20 fetuses. A single treatment with both chemicals on GD9‐induced TSR, with the incidence highest when administered at 7:00 Am , decreasing gradually when administered later. This trajectory was clearer in rats treated with 5‐FC than with SAL. The critical period of TSR induction is shorter in rats administered 5‐FC than SAL. The characteristics of the critical window may cause variability in the incidence of TSR observed in developmental toxicity studies.