Differential effects of thyroxine and cortisone on jejunal sucrase expression in suckling rats.
Effects of thyroxine (T4) and cortisone (C) on developmental expression of jejunal immunoreactive sucrase-isomaltase (S-I) and sucrase activity in suckling rats were studied to determine whether these hormones have distinctive actions. Immunoreactive S-I and sucrase activity were absent in infant rats and appeared simultaneously on days 16-18, when cells expressing S-I protein were detected at the villus base. By day 22, the entire jejunal mucosal surface was covered by new cells expressing immunoreactive S-I. Jejunal S-I content surged to adult levels on day 22, whereas the sucrase activity of immunoreactive S-I protein increased continuously until day 32. Administration of 12.5 nmol of T4 or 1.25 mumol of C on day 12 induced precocious expression of jejunal sucrase activity on day 15. T4 also induced sucrase activity in adrenalectomized rats without increasing serum corticosterone concentrations. Both T4 and C appeared to exert their effects in crypt cells, since immunoreactive S-I protein appeared only in villus base cells 24 h after administration. Pulse labeling of [14C]leucine showed that both hormones evoked de novo synthesis of S-I. The S-I induced by C had significantly higher sucrase activity than that induced by T4. We conclude that postnatal development of sucrase activity results from de novo synthesis of S-I with progressively higher catalytic activity until day 32 and these developmental processes are sequentially modulated by thyroid and adrenocortical hormones.
Yeh
K Y
KY
Division of Gastroenterology, St. Luke's-Roosevelt Hospital Center, New York, New York 10025.
Yeh
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M
Holt
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PR
D000315:Adrenalectomy; D000375:Aging; D000818:Animals; D003348:Cortisone / Q000494:pharmacology*; D004790:Enzyme Induction; D005455:Fluorescent Antibody Technique; D007583:Jejunum / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development*; D007773:Lactates / Q000096:biosynthesis; D009097:Multienzyme Complexes / Q000096:biosynthesis*; D024510:Muscle Development; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013393:Sucrase / Q000096:biosynthesis*; D013394:Sucrase-Isomaltase Complex / Q000096:biosynthesis*; D013974:Thyroxine / Q000494:pharmacology*
D007773:Lactates; D009097:Multienzyme Complexes; D013394:Sucrase-Isomaltase Complex; D013393:Sucrase; D013974:Thyroxine; D003348:Cortisone