| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1995: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1994: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
In the present study, growth hormone (GH) induction by glucocorticoid was successfully reproduced in vitro, and using this in vitro system, the molecular mechanisms underlying the GH-induction in the fetal pituitary gland was analyzed.
The pituitary glands of E18 fetuses were incubated in vitro in serum free MEM-alpha with or without an addition of DEX (50nM). After 24h incubation, GHmRNA was accumulated only in the tissue incubated with DEX to a compatible level to that of control E19 fetuses. This ihdicates that the primary site of the DEX action is the pituitary gland and the influences of maternal factors, placenta or fetal hypothalamus are not prerequisite with respect to the initiation of GH production in the fetal pituitary gland. When E17 pituitaries were incubated with DEX,a distinct reduction of the level of GHmRNA accumulation was noted. This is considered to be the consequence of the difference in the number of tha cells which are capable of responding DEX.DEX induction of GHmRNA was not evident after 5 or 10 h incubation, however, if DEX was present in the medium for first 10h of the 24h-incubation, the continuous presence of DEX was not required for GH induction for the rest of incubation period. An addition of the cycloheximide, or puromycin, inhibitors of protein synthesis, completely inhibited the GH induction by DEX.These results taken as a whole suggest that the induction of GHmRNA in the fetal pituitary gland by DEX is mediated by unknown factor which is produced in pituitary gland in response to DEX,and probably activates the GH gene transcription.
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