PubMed · 2846967
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M A Peat. THCA calibrators and controls.. https://doi.org/10.1093/jat%2F12.4.239
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Gas chromatographic-mass spectrometric methods of analysis for the detection of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid, a major metabolite of delta 9-tetrahydrocannabinol, are reviewed. Emphasis is on analytical methodology including numerous derivatization techniques developed specifically for this analyte. The majority of procedures cited in the literature were developed to detect this metabolite in the blood and urine of man.
Whole-cell voltage-clamp techniques were used to study the comparative effects of delta-9-tetrahydrocannabinol (THC) and its principal metabolite, 11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC), on the voltage-gated sodium current in neuroblastoma cells. The parent compound markedly depressed the inward sodium current with minimal reduction of the outward current, demonstrating that the effects of the drug were related to the membrane potential. In addition, THC reduced the reversal potential, indicating that the drug modified the ion selectivity of the channel. 11-OH-THC similarly depressed inward sodium current; however, in marked contrast to the effects of the parent compound, the drug equally depressed the outward voltage-gated sodium current, indicating that its effects were not related to the membrane potential. Furthermore, 11-OH-THC differed from THC in that it did not alter the reversal potential. The results demonstrate that THC and its 11-OH metabolite both reduce inward sodium current, but their effects on the outward current and ion selectivity are distinctly different. The sum of the actions of these two cannabinoids on the voltage-gated sodium channel provides a plausible cellular basis for THC's depression of action potentials in vivo and for some of its central depressant effects.
A simple liquid-liquid extraction and GC/MS-method for detection and quantification of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) from merely 1 ml urine is described. The derivatisation to the methyl ester was carried out using methyl iodide and mefenamic acid was used as internal standard. Experiments with urine spiked with 15 ng THC-COOH/ml resulted in a recovery of 91%. Excellent linearity was obtained over the range 5-100 ng/ml.