[Total lactate dehydrogenase activity of perilymph, plasma and cerebrospinal fluid in unstressed and noise stressed guinea pigs].

The total activity of lactate dehydrogenase (LDH) of perilymph (PL), plasma, and cerebrospinal fluid (CSF) of unexposed and sound-exposed guinea pigs was examined with due consideration of the principal sources of error. To test the purity of PL samples, protein, potassium, and sodium were determined simultaneously (Table 1). The LDH was analysed fluorometrically. It was found that there are considerable differences in the LDH activities of PL, CSF, and plasma (Table 2). The mean activity of PL was three to four times higher than that of CSF and only about half that of plasma. No significant difference was found between the PL in scala tympani and scala vestibuli. The most frequent LDH values of the individual fluids (Fig. 2) were somewhat lower than the mean values calculated. Immediately (less than or equal to 60 min) after exposing the animals to wide-band noise at an intensity of 140 dB SPL for 10 min, the mean PL values of the scala tympani and scala vestibuli were found to be somewhat higher than in unexposed animals (Table 3). Eighteen hours after the exposure, slightly higher activity was only detectable in PL of the scala vestibuli. The differences were not found to be significant. The LDH values of CSF and plasma remained unchanged both less than or equal to 60 min and 18 h after noise exposure.