ISSN:
1365-2826
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Trophic effects of 17β-estradiol (βE2) on in vitro developing hypothalamic cells have been reported. Insulin-like growth factor I (IGF-I) is also a potent trophic factor for cultured hypothalamic cells. An interaction between sexual steroids and insulin-like growth factors (IGFs) in modulating growth of hypothalamic cells has been suggested. Thus, we tested whether βE2 modulates the levels of IGF-I, its membrane receptor and its binding proteins in rat hypothalamic culturs. Using both neuron- and glial-enriched cultures obtained from fetal rat hypothalami we found that addition of βE2 elicited a significant increase in IGF-I receptor levels in neurons, without affecting its affinity. On the other hand, the three different IGF-binding proteins (IGFBPs) found in the conditioned medium of the cultures were differentially modulated by βE2 in the two types of cells studied. Overall, neuronal cultures produced greater amounts of IGFBPs after treatment with βE2, with IGFBP2 reaching significantly higher levels. On the contrary, treatment with βE2 did not significantly alter the amounts of IGFBPs produced by glial cells. Finally, the levels of immunoreactive IGF-I found either in the medium or in cellular extracts in both neuronal and glial cultures were not modified by treatment with βE2. These results strongly support previous observations of a trophic synergistic interaction between IGFs and βE2 on hypothalamic cells. Thus, an increase in IGF-I receptors and/or IGFBPs after exposure to βE2 may result in an enhanced response of hypothalamic neurons to IGF-I. Further, the present findings strengthen our recent observation that the effects of βE2 on hypothalamic glial cells are neuronally mediated, since IGF-I receptors and IGFBPs are modulated by this sex hormone in neurons, but not in glial cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2826.1993.tb00482.x
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