Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two nitroxide spin labels called PCA and TES have been used experimentally as contrast enhancing agents in magnetic resonance imaging. Pharmacokinetic data for these nitroxides, after intravenous administration to three dogs at two dose levels (0.1 and 2.5 mmole/kg), are presented. In this dose range, the clearance (13 ml/ min-kg) and half-life (22 min) of PCA stayed almost constant while TES clearance decreased (28 to 12 ml/min-kg) and half-life increased (8 to 17 min) with dose. The urinary recovery, determined from the sum of the nitroxide and its corresponding hydroxylamine, was 85 to 90% for both PCA and TES. PCA was investigated in more detail because of its lower clearance value and its lack of dose-dependence. The major pathways of elimination are renal excretion and metabolic reduction to the corresponding hydroxylamine which is eliminated by renal excretion. We estimated renal clearance of both PCA (5.5 ml/ min-kg) and its hydroxylamine (3.7 ml/min-kg) to be close to glomerular filtration rate (4 ml/min-kg) in the dog, while the metabolic clearance (7.5 ml/min-kg) was slightly higher. Approximately 35 % of the administered dose of PCA was excreted unchanged and half was reduced in the body.
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PMID:Pharmacokinetics of two prototype nitroxide spin labels for contrast enhancement in magnetic resonance imaging. 2427 11

Paramagnetic nitroxyl-containing compounds have been useful as contrast agents in magnetic resonance imaging (MRI) experiments in animals. Preliminary information on the metabolic fate, pharmacokinetic behavior, stability in tissues, and chemical reduction of two prototypic nitroxides, PCA and TES, is presented. In the dog TES was eliminated more rapidly than PCA. More than 80 % of the dose of both nitroxides was recovered in urine within 6 hours. Nitroxides were reduced in vivo to their corresponding hydroxylamines. No other metabolite was observed. Measured reducing activity in tissue homogenates was greater in liver or kidney than in brain, lung or heart. In each tissue PCA was more stable than TES. PCA was also more resistant to reduction by ascorbic acid at physiologic pH. These preliminary results favor the use of PCA, a pyrrolidinyl nitroxide, over TES, a piperidinyl nitroxide, for MRI contrast enhancement.
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PMID:Pharmacokinetics and metabolic fate of two nitroxides potentially useful as contrast agents for magnetic resonance imaging. 2427 29