Measurement of the acute metabolic response to hypoxia in rat tumours in vivo using magnetic resonance spectroscopy and hyperpolarised pyruvate.

To estimate the rate constant for pyruvate to lactate conversion in tumours in response to a hypoxic challenge, using hyperpolarised (13)C1-pyruvate and magnetic resonance spectroscopy.
Hypoxic inspired gas was used to manipulate rat P22 fibrosarcoma oxygen tension (pO2), confirmed by luminescence decay of oxygen-sensitive probes. Hyperpolarised (13)C1-pyruvate was injected into the femoral vein of anaesthetised rats and slice-localised (13)C magnetic resonance (MR) spectra acquired. Spectral integral versus time curves for pyruvate and lactate were fitted to a precursor-product model to estimate the rate constant for tumour conversion of pyruvate to lactate (kpl). Mean arterial blood pressure (MABP) and oxygen tension (ArtpO2) were monitored. Pyruvate and lactate concentrations were measured in freeze-clamped tumours.
MABP, ArtpO2 and tumour pO2 decreased significantly during hypoxia. kpl increased significantly (p<0.01) from 0.029±0.002s(-1) to 0.049±0.006s(-1) (mean±SEM) when animals breathing air were switched to hypoxic conditions, whereas pyruvate and lactate concentrations were minimally affected by hypoxia. Both ArtpO2 and MABP influenced the estimate of kpl, with a strong negative correlation between kpl and the product of ArtpO2 and MABP under hypoxia.
The rate constant for pyruvate to lactate conversion, kpl, responds significantly to a rapid reduction in tumour oxygenation.
AuthorsJoanne E Bluff, Steven Reynolds, Stephen Metcalf, Tooba Alizadeh, Samira M Kazan, Adriana Bucur, Emily G Wholey, Becky A S Bibby, Leigh Williams, Martyn N Paley, Gillian M Tozer
JournalRadiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology (Radiother Oncol) Vol. 116 Issue 3 Pg. 392-9 (Sep 2015) ISSN: 1879-0887 [Electronic] Ireland
PMID25824978 (Publication Type: Journal Article)
CopyrightCopyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

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