Thyroid Hormone Action on Biosynthesis of Somatostatin by Fetal Rat Brain Cells in Culture*

Frailes, Maria Teresa de los; Cacicedo, Lucinda; Lorenzo, María Jesús López; Fernandez, G.; Sánchez‐Franco, Franco

doi:10.1210/endo-123-2-898

Cited by 35 publications

(10 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, recent preliminary data from our laboratory show that long-term hypothyroidism decreases not only SRIF con tent but also SRIF mRNA [II], Therefore, the duration of hypo thyroidism appears to be fundamental for this action. Further more, the stimulatory action of thyroid hormones on IR-SRIF synthesis has recently been demonstrated in normal rat hypo thalamic cells in culture [20], In agreement with previous ontogenesis studies [21], our data show that hypothalamic IR-GRF increased to adult levels coinciding with sexual maturity. These findings suggest that tes tosterone may play a role on the GRF increase induced by pu berty, since it has been demonstrated that testosterone increases both GRF-mRNA production in vivo [22] and IR-GRF secre tion in cultured rat hypothalamic cells [23], In the present study, the most consistent influence of hypothyroidism on hypotha lamic IR-GRF concentrations was the abolition of the puberal rise and the decrease observed in long-term hypothyroidism.…”

Section: Hypothalamic Ir-grf and Ir-srifsupporting

confidence: 93%

Influence of Hypothyroidism Duration on Developmental Changes in the Hypothalamic Factors Implicated in Growth Hormone Secretion in the Male Rat

Varela

Cacicedo²,

Fernandez³

et al. 1991

Neuroendocrinology

View full text Add to dashboard Cite

The effects of hypothyroidism duration on several factors implicated in GH secretion control were studied in the male rat at different maturity stages, ranging from the peripuberal period to adulthood. Thyroid ablation was performed on 22-day-old Wistar male rats maintained on a low iodine diet (T group). Age-paired controls (C group) were fed with the same diet, supplemented with potassium iodide. Subgroups of T and C animals (aged 32, 42, 52, 82 and 112 days) were studied 10, 20, 30, 60 and 90 days after surgery. After pentobarbital anesthesia, jugular blood was withdrawn before and 5 min after an intravenous TRH stimulus, for GH assay. Hypothalamic and pituitary tissues were obtained in order to measure GH, immunoreactive somatostatin (IR-SRIF) and growth hormone-releasing factor (IR-GRF). Growth rate and serum testosterone confirmed that C rats reached sexual maturity by day 30 of the study. Mean ± SE serum GH (ng/ml) increased (p < 0.05) in C animals from day 10 (38.5 ± 5) to day 30 (67.4 ± 7.3), with no significant variations thereafter. The same time sequence pattern was observed in pituitary GH concentrations. In T rats, both serum and pituitary GH decreased progressively from day 10 to 90, being significantly lower than in C at all times of the study. No GH response to TRH could be found in C groups. In contrast, GH increased significantly (p < 0.05) in T animals after TRH at days 20 and 30. Hypothalamic IR-SRIF concentrations (ng/mg protein) increased (p < 0.05) to adult levels in C rats between days 10 (15.7 ± 3) and 30 (26.3 ± 2.8), remaining unchanged thereafter. T animals showed the same pattern up to day 60. On day 90, IR-SRIF decreased abruptly in T (9.7 ± 2.9) as compared to both normal peers (30.8 ± 7.2; p < 0.01) and 60-day T rats (24.3 ± 5.1; p < 0.05). Hypothalamic IR-GRF (ng/mg protein) also increased (p < 0.05) between day 10 (2.9 ± 0.3) and 30 (4.3 ± 0.7) in C animals. This puberal rise did not occur in 30-day Trats, whose IR-GRF was lower (2.6 ± 0.3; p < 0.01) than in C. It can thus be concluded that a decrease in pituitary GH availability is not the only factor implicated in the abnormal GH secretion found in hypothyroidism. An enhanced GH response to TRH was found to coexist with a 94% reduction in pituitary GH content on days 20 and 30 of hypothyroidism. In the normal rat, hypothalamic IR-SRIF and IR-GRF content increased to adult values in the puberal period. The influence of hypothyroidism on the hypothalamic IR-SRIF content is closely related to its duration, occurring only in long-term thyroid deprivation. Hypothyroidism also prevents the puberal rise of IR-GRF, but does not affect the concomitant increase of IR-SRIF. The blunting of the puberal rise in IR-GRF occurs despite the normal testosterone increase in hypothyroid rats, suggesting that the diminished concentration of thyroid hormone impairs the testosterone-mediated IR-GRF rise.

show abstract

Section: Hypothalamic Ir-grf and Ir-srifsupporting

confidence: 93%

Influence of Hypothyroidism Duration on Developmental Changes in the Hypothalamic Factors Implicated in Growth Hormone Secretion in the Male Rat

Varela

Cacicedo²,

Fernandez³

et al. 1991

Neuroendocrinology

View full text Add to dashboard Cite

show abstract

“…The progressive increase with aggregate age in NPY-IR measured in the medium indicates that the aggregates are the source of the immunoreactive substance. It is interesting to note that the amounts of peptides secreted from other peptidergic neurons in culture relative to the cell content of the peptides varies from one cell type to another and the brain region; the amounts can be less [41][42][43], the same [43] or greater [44] (this study). One possibility is that the develop mental increase in the biosynthesis of NPY exceeds that of the formation of the intracellular storing organelles, i.e.…”

Section: Discussionmentioning

confidence: 84%

Regulated Production and Secretion of Immunoreactive Neuropeptide Y by Aggregating Fetal Brain Cells in Cultures

Barnea¹,

Hajibeigi²,

Cho³

et al. 1991

Neuroendocrinology

View full text Add to dashboard Cite

The aim of this study was to establish a culture system of fetal brain cells that could serve as a model for the study of the developmental regulation of the neuropeptide Y(NPY) neuron. Single cell suspensions were prepared from the hypothalamic-olfactory tubercle region of 18-day-old rat fetuses, and aggregates were formed by incubation in serum-free medium under constant rotation. Aggregate formation was complete within 24–48 h, and cultures were maintained for up to 23 days. The content of immunoreactive (IR) NPY in the medium and in the aggregates increased progressively with time in culture and at each time point, the medium contained 5- to 10-fold more NPY-IR. A 48-hour exposure to forskolin resulted in a 2-fold increase in the accumulation of NPY-IR in the aggregates and in the medium, indicating that both production and secretion of NPY are regulated by the cAMP intracellular pathway. Sephadex gel filtration revealed the presence of proNPY- and NPY-size substances. The ratio of NPY- to proNPY-size substances increased progressively with age of the aggregates as well as in tissues obtained from perinatal rats of comparable age. Thus, production and secretion of NPY-IR in the cultured aggregates are regulated processes and hence, this culture system can serve as a model to study regulatory processes in the developing NPY neuron.

show abstract

“…Preparation of primary long-term dispersed cell cultures of fetal rat cerebral cortex was done as previously described (de 10s Frailes et al, 1988). Timed pregnant Wistar rats were raised in our laboratory.…”

mentioning

confidence: 99%

Effect of potassium-induced depolarization on somatostatin gene expression in cultured fetal rat cerebrocortical cells

Franco

Frailes

et al. 1994

J. Neurosci.

View full text Add to dashboard Cite

The stimulatory effect of potassium depolarization upon somatostatin (SS) mRNA levels in primary cultures of fetal cerebrocortical cells was analyzed. Depolarizing stimuli, such as 56 mM K+ exposure for 30 min, elicited an increase in immunoreactive somatostatin (IR-SS) release to the media and decreased SS mRNA levels. These were increased when exposure to depolarization stimuli was prolonged up to 3 or more hr. At this time, potassium (30 and 56 mM) acted as a secretagogue, stimulating SS secretion, but was also effective in stimulating SS mRNA levels, suggesting that SS secretion can be coupled to SS mRNA accumulation. These changes were inhibited by the Ca2+ channel antagonist verapamil. In contrast, Na+ channel blockade by TTX did not modify the 24 hr potassium-induced increase in SS mRNA, although it partially abolished potassium-induced SS secretion. Examination of the rate of disappearance of SS mRNA levels after inhibition of mRNA transcription by actinomycin-D revealed that K+ stimulation of cerebrocortical cells stabilized the SS mRNA. These results suggest that the induction of SS mRNA expression by K+ is dose dependent, and involves the modulation of ion channels. The time-course study confirmed that the K(+)-induced SS mRNA accumulation is time dependent, chronic activation of the Ca2+ channels being necessary to stimulate SS gene expression. K+ stimulation may also increase the level of SS mRNA in cerebrocortical cells by reducing its rate of degradation.

show abstract

Thyroid Hormone Action on Biosynthesis of Somatostatin by Fetal Rat Brain Cells in Culture*

Cited by 35 publications

References 39 publications

Influence of Hypothyroidism Duration on Developmental Changes in the Hypothalamic Factors Implicated in Growth Hormone Secretion in the Male Rat

Influence of Hypothyroidism Duration on Developmental Changes in the Hypothalamic Factors Implicated in Growth Hormone Secretion in the Male Rat

Regulated Production and Secretion of Immunoreactive Neuropeptide Y by Aggregating Fetal Brain Cells in Cultures

Effect of potassium-induced depolarization on somatostatin gene expression in cultured fetal rat cerebrocortical cells

Contact Info

Product

Resources

About