Expression of troponin subunits in the rat renal afferent arteriole
Bibliographic record
Abstract
Abstract Vascular smooth muscle cells of the renal afferent arteriole are unusual in that they must be able to contract very rapidly in response to a sudden increase in systemic blood pressure in order to protect the downstream glomerular capillaries from catastrophic damage. We showed that this could be accounted for, in part, by exclusive expression, at the protein level, of the “fast” (B) isoforms of smooth muscle myosin II heavy chains in the afferent arteriole, in contrast to other vascular smooth muscle cells such as the rat aorta and efferent arteriole which express exclusively the “slow” (A) isoforms (Shiraishi et al. (2003) FASEB. J . 17 , 2284–2286). As contraction of the more rapidly contracting striated (skeletal and cardiac) muscles is regulated by the thin filament‐associated troponin (Tn) system, we hypothesized that Tn or a Tn‐like system may exist in afferent arteriolar cells and contribute to the unusually rapid contraction of this tissue in response to increased intraluminal pressure. We examined the expression of TnC (Ca 2+ ‐binding subunit), TnI (inhibitory subunit), and TnT (tropomyosin‐binding subunit) in vascular smooth muscle cells of the rat renal afferent arteriole at the mRNA level. Fast‐twitch skeletal muscle and slow‐twitch skeletal muscle/cardiac TnC isoforms and slow‐twitch skeletal muscle and cardiac TnI isoforms were detected by reverse transcription‐polymerase chain reaction (RT‐PCR) and confirmed by cDNA sequencing. Furthermore, cardiac and slow‐twitch skeletal muscle TnI isoforms, but not fast‐twitch skeletal muscle TnI, were detected in isolated afferent arterioles at the protein level by proximity ligation assay. Finally, striated muscle myosin II heavy chain expression was identified in isolated rat afferent arterioles by RT‐PCR. We conclude that, in addition to Ca 2+ ‐mediated phosphorylation of myosin II regulatory light chains, contraction of the afferent arteriole may be regulated by a mechanism normally associated with the much more rapidly contracting cardiac and skeletal muscles, which involves Ca 2+ binding to TnC, leading to alleviation of inhibition of the actomyosin MgATPase by TnI and tropomyosin and rapid contraction of the vessel.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".