kreas meat
creatin creatine
creatine creatinine
Creatinine = the dehydrated part remaining from [[creatine]]
Phosphocreatine is an energy storage intermediary of ATP, ATP + creatine ⇌ phosphocreatine + ADP + energy
Source and Excretion
Source
- Meat contains a large amount of creatine (the cooking process dehydrates creatine into creatinine); consuming meat provides intake
- Creatine is synthesized mainly in the liver and kidneys, with 95% transferred to muscles where it works with ATP for energy supply; about 1-2% of creatine/phosphocreatine is metabolized and excreted daily as creatinine
- More muscle means more creatine and consequently more creatinine is metabolized (1 mg creatinine is produced per every 20 g of muscle metabolism)
Excretion
- 85% filtered by glomerulus + 15% tubular secretion
- Tubules do not reabsorb creatinine (in contrast, 90% of uric acid is reabsorbed by tubules)
Physiology
A 70 kg male has about 120 g of creatine/phosphocreatine in the body, consumes about 1% daily (around 2 g), supplements about 1 g from food, and synthesizes about 1 g in liver and kidneys
Pathology
Severe kidney damage, renal insufficiency
[[Endogenous creatinine clearance]]
Influencing factors
Height, weight, and gender (muscle mass) determine creatinine production amount
Age (renal function) determines creatinine clearance rate
Medications
- Sulfamethoxazole, cimetidine inhibit tubular secretion (the tubules use cation pumps to excrete creatinine, these drugs competitively inhibit this process)
- Fenofibrate, sodium phosphocreatine increase creatinine production
Abnormal testing
| Drug | Enzymatic | Jaffe’s |
|---|---|---|
| Cefotaxime | / | (+) |
| Cefotiam | / | (±) |
| Cefpirome | / | (+) |
| Cefazolin | / | (+) |
| Lidocaine | (+) | (±) |
| Dopamine | (-) | (-) |
| Dobutamine | (-) | (±) |
| Acetohydrazide | Not Known | (+) |
| Aspirin | (-) | (+) |
| Acetaminophen | (-) | (+) |
| Antipyrine | (-) | (+) |
| Streptomycin | Not Known | (+) |
| Phenylpropanolamine | (-) | Not Known |
| Calcium phenylsulfonate | - | Not Known |
Monitoring
[[Serum creatinine (scr)]]
[[Urine creatinine]]
Creatinine absolute value is influenced by food, muscle mass, etc., so a high [[serum creatinine (scr)]] does not equal poor renal function; best evaluated via [[endogenous creatinine clearance]] test
Care
Meat is rich in creatine, but cooking converts creatine into creatinine, increasing metabolic load