Creatine synthesis: the origin of creatine in rat milk
Bibliographic record
Abstract
Creatine serves as an important energy buffer and shuttle system in cells. Approximately 1.7%/day of the body's creatine pool is spontaneously converted to creatinine and excreted in the urine. This must be replaced by a combination of diet and synthesis. During lactation there may be an additional requirement due to the provision of creatine to the milk. Our objectives were (1) to quantify milk creatine in lactating rats, (2) to determine the origin of milk creatine, and (3) to determine the activities of the enzymes of creatine synthesis in lactating rats. We determined the origin of milk creatine by administering 14 C‐creatine to lactating rats, followed by determination of its isotopic enrichment in milk and plasma. Since these isotopic enrichments were identical, we conclude that milk creatine is extracted from the blood. Supporting this is our failure to find significant activities of the enzymes of creatine synthesis in mammary glands. Milk creatine amounted to about 13 μmol/day, which is equivalent to 25% of the creatine lost by conversion to creatinine. The first and limiting enzyme in creatine synthesis was not increased in activity during lactation; neither was the renal output of guanidinoacetate. We conclude that there is only a modest increase in the need to provide creatine during lactation and that this may be largely provided by hyperphagia when creatine is present in the food. Supported by CIHR grant 97851. Grant Funding Source : Canadian Institute for Health Research
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".