Continuous Noninvasive Monitoring of pH and Temperature in Rat Walker 256 Carcinoma During Normoglycemia and Hyperglycemia23

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Abstract
The extracellular pH and temperature of Walker 256 carcinoma and of normal subcutaneous tissue were measured continuously in unanesthetized female Sprague-Dawley rats for up to 20 hours following glucose or galactose administration. The pH was monitored with flexible glass electrodes contained in micropore chambers implanted in the flank of a rat. Temperature was measured with miniature thermistor probes incorporated in the tumor or in subcutaneous tissue. The pH in the untreated Walker 256 carcinoma decreased linearly from approximately 7.3 to 6.2 with increasing tumor mass up to 50 g. Administration of glucose (6 g/kg body wt, ip) in tumor-bearing rats increased glucose concentrations in blood and tumor, as well as lactic acid concentration in tumor, and had no significant effect on lactic acid concentration in blood. Plasma volume was not affected by either glucose or galactose loading as compared to that in rats given saline alone. However, the blood viscosity increased by up to 30% within 30 minutes after galactose injection, but not after glucose injection, and this significant difference in viscosities persisted for approximately 6 hours after glucose and galactose injections. In small tumors (20 g) was not as uniform; the pH decreased by about 0.5 to 1 pH unit for only a brief period. After galactose injection, pH in some tumors remained unchanged, whereas in others an average decrease of about 0.2 pH units was observed. The pH in normal tissue was not affected by glucose or galactose administration. Both glucose and galactose decreased tumor temperature by about 7°C.