Characterization of branchial lead-calcium interaction in the freshwater rainbow trout <i>Oncorhynchus mykiss</i>
Bibliographic record
Abstract
The mechanism of branchial lead uptake and interplay with Ca(2+) transport was investigated in the freshwater rainbow trout Oncorhynchus mykiss. Lead significantly reduced Ca(2+) influx by approximately 40% and 30% after exposure to 2.3+/-0.1 and 1.4+/-0.2 micromol l(-1) dissolved lead, respectively, for 0-48 h. Acute inhibition of Ca(2+) influx by lead exhibited typical Michaelis-Menten kinetics with an approximate 16-fold increase in K(m), whereas J(max) values did not significantly change, yielding an inhibitor constant (K(i,Pb)) of 0.48 micromol l(-1). Alternative analyses suggest the possibility of a mixed competitive/non-competitive interaction at the highest lead concentration tested (4.8 micromol l(-1)). Branchial lead accumulation was reduced with increasing waterborne Ca(2+) concentrations, suggesting a protective effect of Ca(2+) against lead uptake at the gill. The apical entries of Ca(2+) and lead were both inhibited (55% and 77%, respectively) by the addition of lanthanum (1 micromol l(-1)) to the exposure water. The use of cadmium (1 micromol l(-1)) and zinc (100 micromol l(-1)) as voltage-independent calcium channel competitors also reduced branchial lead uptake by approximately 56% and 47%, respectively. Nifedipine and verapamil (up to 100 micromol l(-1)), both voltage-dependent calcium channel blockers, had no effect on gill lead accumulation. CaCl(2) injection reduced both Ca(2+) and lead uptake by the gills. This suggests transport of lead through apical voltage-independent calcium channels, similar to the entry of Ca(2+). High-affinity Ca(2+)-ATPase activity was not acutely affected by lead, but a significant 80% reduction in activity occurred during exposure for 96 h to 5.5+/-0.4 micromol l(-1) dissolved lead, indicating a possible non-competitive component to lead-induced Ca(2+) disruption. The effect of lead on Ca(2+) efflux was investigated and found to be insignificant. We conclude that uptake of lead occurs, at least in part, by the same mechanism as Ca(2+), which results in disruption of Ca(2+) influx and ultimately Ca(2+) homeostasis.
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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) | 0.001 | 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 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".