Maturational effect of triiodothyronine and its analog 3,5-dimethyl-3'-isopropyl-L-thyronine on sucrase activity in the small intestine of the developing rat.
In this study we compared the effect of 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) with that of triiodothyronine (T3) on sucrase activity in the small intestine of the fetal and suckling rat. DIMIT (5 micrograms/100 g BW) was injected into pregnant Sprague--Dawley rats on days 17-20 of gestation and DIMIT (10 and 50 micrograms/100 g BW) and T3 (10 and 50 micrograms/100 g BW) were given subcutaneously to two groups of sucklings on days 4-7 and 11-14. Fetal animals were sacrificed on day 21 of gestation; sucklings on days 8 and 15. Sucrase activity in the proximal, middle, and distal small intestine was assayed. DIMIT and T3 suppressed serum thyroid-stimulating hormone (TSH) in the fetus and suckling. Sucrase activity was increased in all small intestinal segments in the fetal and older suckling groups. In the younger sucklings the effect was seen only in the middle and distal segments. In both fetal and suckling groups the sucrase response was dose related. Thus, DIMIT has a thyromimetic effect on development of sucrase activity. The lack of sucrase reactivity in the proximal segment of the younger (8-day-old) sucklings to the administration of either DIMIT or T3 is interesting but unexplained.
D000818:Animals; D000833:Animals, Suckling / Q000378:metabolism; D005333:Fetus / Q000201:enzymology / Q000378:metabolism; D007421:Intestine, Small / Q000201:enzymology* / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013393:Sucrase / Q000378:metabolism*; D013970:Thyronines / Q000494:pharmacology*; D013972:Thyrotropin / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*
D011506:Proteins; D013970:Thyronines; D014284:Triiodothyronine; C022861:3,5-dimethyl-3'-isopropyl-L-thyronine; D013972:Thyrotropin; D013393:Sucrase