Measurement of protein synthesis by the phenylalanine flooding dose technique: effect of phenylalanine and anaesthesia on plasma electrolyte, enzyme and metabolite levels

Is there a correlation between taurine levels and xenobiotic-induced perturbations in protein synthesis?: a study with tetracycline in rats

Changes in urinary levels of taurine have been reported in rats following treatment with various xenobiotics including those which alter protein synthesis and/or are hepatotoxic. This paper reports on the time course of the urinary elevation of taurine following treatment of rats with tetracycline (50, 150 and 200 mg.kg-1). Maximum taurine excretion occurred 8-12 h following dosing. Serum albumin and total protein were significantly lower after 24 h (200 mg.kg-1). The increase in urinary taurine was dose-related and reflected in the raised serum levels of taurine 24 h after dosing. Serum and urinary protein and [3H]-leucine incorporation into acid precipitable protein in liver and muscle were reduced by tetracycline (100, 150 and 200 mg.kg-1) 10 h after dosing. The reduction in protein synthesis was correlated with increased urinary and serum levels of taurine at 10 h. The use of taurine as a non-invasive marker of protein synthesis is discussed.

Several anesthetics, but not diethyl ether, cause marked elevation of serum parathyroid hormone concentration in rats

The effects of anesthetics on serum parathyroid hormone (PTH) concentrations were determined by a new homologous two-site immunoradiometric assay for rat PTH. Serum PTH concentrations (mean +/- SE) from ether-anesthetized rats (14.7 +/- 1.5 pg/ml, n = 22) were not significantly different from those of decapitated unanesthetized female rats (13.0 +/- 1.8 pg/ml, n = 21). Serum PTH concentrations in pg/ml (n = 4-14) for other anesthetics tested were: ketamine, 12.5 +/- 1.1; Na pentobarbital, 23.3 +/- 2.4; methoxyflurane (inhalation), 42.2 +/- 6.8; and xylazine combined with ketamine, 51.4 +/- 11.3 pg/ml. The latter two concentrations were significantly (p < 0.001) higher than the values for all other anesthetics and decapitation. Elevation of serum PTH induced by pentobarbital or ketamine + xylazine increased with time under anesthesia. Neither serum Ca2+ concentrations nor pH differed among any of the groups. We conclude that anesthesia induced by pentobarbital, methoxyflurane, or ketamine + xylazine in rats leads to a marked elevation of serum PTH levels that appears to be related to the duration of anesthesia and not due to any measurable fall in serum Ca2+.