Hepatic Creatine Synthesis in the Rat
Bibliographic record
Abstract
Cr (Cr) and Cr-phosphate play a key role in energy metabolism. Approximately 1.7% of the body’s total Cr is lost by cyclization to creatinine per day. Replacement of this Cr occurs via a combination of diet and synthesis. Cr synthesis requires just two enzymes, arginine:glycine amidinotransferase (AGAT) which catalyzes the formation of guanidinoacetate (GAA) from glycine and arginine, and guanidinoacetate N-methyltransferase (GAMT) which employs S-adenosylmethionine to methylate GAA to Cr. In the rat, high activities of AGAT are found in the kidney and of GAMT in the liver which suggests the occurrence of an inter-organ pathway for Cr synthesis. We have, therefore, investigated Cr synthesis by rat liver, both in vivo and in vitro. Rat hepatocytes produce Cr from GAA and this is increased by incubation with methyl group donors, methionine or betaine with homocysteine. Hepatic GAA uptake in vivo was determined in rats fed a Cr-free diet as well as in rats fed a diet supplemented with 0.4% Cr, by sampling from an artery and from the hepatic and portal veins. Arterial [GAA] was 5.61 μM and 2.22 μM, respectively, in the rats fed the Cr-free and Cr-supplemented diet. We found a significant uptake of GAA across the livers of the rats fed the Cr-free diet but no significant uptake in those fed the Cr-supplemented diet. There was no significant difference in GAMT activity between the two diet groups. Supported by CIHR.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".