[Lactate and pyruvate concentrations in perilymph, blood, and cerebrospinal fluid of guinea pigs]

Lactate and pyruvate were studied comparatively in perilymph (PL), blood, and cerebrospinal fluid (CSF) of anesthetized guinea pigs. Arterial blood pressure, heart and respiration rate (Fig. 1), and arterial blood-gas state (Table 2) were simultaneously checked in a group of the animals. The metabolites were determined enzymatically by using the fluorometric technique. The studies have shown (Table 1) that both the lactate and the pyruvate concentrations are in PL at a similar rate (about 3:1) higher than in native blood and also higher than in CSF. The metabolite values of blood, especially the lactate values, were lower when blood was taken alone, e.g., more physiological, than in the case when CSF and PL had been sampled before. The lactate/pyruvate ratios of Pl are somewhat higher than the blood ratios. The ratio of CSF was found to be lower. The high metabolite levels in PL suggest an intracochlear origin. A direct perilymphatic lactate origin could not be detected.