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Abstract
31P-NMP, surface coil spectra of three subcutaneously implanted rat tumours (Morris hepatoma 7777, GH3 prolactinoma, Walker carcinosarcoma) and an N-methyl-N-nitrosourea induced rat mammary adenocarcinoma at different stages of growth were obtained and compared with histological sections taken immediately after NMR acquisitions. Metabolite ratios (phosphocreatine (PCr)/beta nucleoside triphosphate (beta NTP), PCr/Pi, beta NTP/Pi) calculated from the NMR spectra were compared with ratios obtained from acid extracts of tumours of similar size. Measurements of creatine and ADP were also made. Three of the tumours showed positive correlations between increasing tumour size and decreasing metabolite ratios measured both by NMR and in extracts, whereas the Walker carcinosarcoma showed no correlation between size and any parameters measured. Phosphorus metabolite ratios, measured in extracts of skin overlying the tumours, indicated a fall in high energy phosphate when there was histological evidence of skin invasion by the tumour. Surface coil 31P-NMR spectra of subcutaneously grown or induced tumours in the rat represent a slowly changing steady state as the tumour increases in size. We conclude that increasing numbers of hypoxic tumour cells, rather than large areas of necrotic tissue, contribute largely to the NMR spectrum.
Highlights
In addition we have freeze-clamped and measured phosphate metabolites in acid extracts of the tissues overlying some of the subcutaneous tumours
We report the results of NMR studies of a variety of subcutaneously implanted rat tumours in vivo, at different time points in their growth, where we have compared the NMR spectra with histological sections of the tumours and with results obtained by hplc and enzymatic assay of acid extracts of the tumours
Tumours were chosen in pairs in increasing sizes; one for the NMR study which was taken for histology after the completion of the NMR collection and one of similar size which was freezeclamped, acid extracted and assayed for high energy phosphates
Summary
Each batch of tumours (Morris Hepatoma 7777, GH3 prolactinoma, Walker carcinosarcoma; for details of tumours see Stubbs et al, 1989) was grown up from a single inoculum or induced by N-methyl-N-nitrosourea (NMU) injection (mammary adenocarcinoma; see Williams et al, 1981). Spectra were obtained from each batch of tumours with a surface coil (Ackerman et al, 1980), either 1, 1.4 or 2 cm diameter, with a 6, 8 or 10 s pulse duration respectively. Due to difficulties in baseline definition and overlapping peaks these integrals may not give true chemical concentrations. For this reason the data in this paper are all expressed as ratios of integrals (except in Table IV), which minimises some of the uncertainties
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