Amplification of desensitization of TSH response to thyrotrophin-releasing hormone (TRH) may be important mechanisms in the regulation of its secretion. We have investigated this possibility in vitro, using monolayer culture of rat anterior pituitary cells. Cells (1–1·5 × 105/250 μl per well) were cultured for 72 h, exposed to TRH or dibutyryl cyclic AMP (dbcAMP) for 6 or 8 h, washed, and then treated for 4 h with various doses of TRH, or with K+ (55 mmol/l) as a non-specific secretagogue. Pretreatment with TRH (20 nmol/l) for 8 h reduced subsequent TSH release: basal release fell to 64% of the control value (1·01±0·10 μg/l pretreated, 1·58 ± 0·16 control) and release in response to TRH (100 nmol/l) to 69% of the control (2·7 ± 0·19 μg/l vs 3·98 ± 0·22); K+ response was reduced to 86% of the control (3·77 ± 0·21 μg/l vs 4·39 ± 0·20), significantly less than the other reductions. The extent of the parallel downward shift of the TRH dose–response curve was proportional to dose and duration of prior TRH exposure. There was no significant change in the dose of TRH required to cause half-maximal TSH release (ED50: pretreated 4·8, control 2·8 nmol TRH/l) suggesting depletion of an intracellular pool of TSH rather than 'desensitization'. After 6-h pretreatment with dbcAMP, subsequent TSH responses were augmented: basal release was 130% of the control, response to TRH (100 nmol/l) was 137% and to K+ it was 132% of the control, with a parallel upward shift of the TRH dose–response curve but no change in cellular TSH content. We suggest that an intracellular pool of TSH exists which can be depleted by prior TRH exposure without a desensitization effect. The size of this pool may be increased by dbcAMP, indicating that cyclic nucleotides may modulate the availability of TSH to an acutely releasable intracellular pool.
J. Endocr. (1986) 108, 211–217
Journal of Endocrinology is committed to supporting researchers in demonstrating the impact of their articles published in the journal.
The two types of article metrics we measure are (i) more traditional full-text views and pdf downloads, and (ii) Altmetric data, which shows the wider impact of articles in a range of non-traditional sources, such as social media.
More information is on the Reasons to publish page.
| Sept 2018 onwards | Past Year | Past 30 Days | |
|---|---|---|---|
| Full Text Views | 6 | 1 | 0 |
| PDF Downloads | 4 | 3 | 0 |
Online ISSN: 1479-6805
Print ISSN: 0022-0795
Strengthening biomedical communities
to advance science and health
CONTACT US
Bioscientifica Ltd | Starling House | 1600 Bristol Parkway North | Bristol BS34 8YU | UK
Bioscientifica Ltd | Registered in England no 3190519
