Activation of EndothelinA Receptors in Frog Adrenocortical Cells Stimulates Both Calcium Mobilization from Intracellular Stores and Calcium Influx through L-Type Calcium Channels
Bibliographic record
Abstract
We have previously shown that endothelin (ET)-1 stimulates corticosterone and aldosterone secretion by the frog adrenal gland through activation of ETA receptors positively coupled to both the adenylyl cyclase and phospholipase C (PLC) pathways. The purpose of the present study was to investigate the involvement of calcium in ET-1-induced stimulation of corticosteroid secretion. Cytoautoradiographic labeling using [125I]ET-1 as a tracer revealed the presence of ET-1 binding sites on adrenocortical cells. Administration of graded concentrations of ET-1 in the vicinity of adrenocortical cells provoked a dose-dependent increase in cytosolic calcium concentrations ([Ca2+]i). ET-1 induced a biphasic response consisting of an immediate and transient peak of [Ca2+]i followed by a plateau phase. Preincubation of the cells with the calcium-ATPase inhibitor thapsigargin or the PLC inhibitor U-73122 reduced the amplitude of the transient phase. Administration of the calcium chelator EGTA or the protein kinase A inhibitor H-89 attenuated the plateau phase. The [Ca2+]i response to ET-1 was markedly reduced during concomitant administration of U-73122 and H-89. Preincubation of the cells with the L-type calcium channel blocker nifedipine attenuated the plateau phase. Corticosteroid secretion from perifused frog adrenal slices was almost completely suppressed by thapsigargin and reduced by nifedipine. Taken together, these data indicate that activation of ETA receptors in frog adrenocortical cells provokes immediate stimulation of PLC, which causes an early mobilization of calcium from intracellular stores, and activates adenylyl cyclase, which results in delayed calcium influx through L-type calcium channels. The resulting increase in [Ca2+]i plays a pivotal role in ET-1-induced corticosteroid secretion.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".