Propylthiouracil alters the expression and activity of glutathione-dependent enzymes in the mouse olfactory mucosa

Biochemical and developmental effects of thyroid and anti-thyroid drugs on different early life stages of Xenopus laevis

The effects of two drugs containing the synthetic thyroid hormone levothyroxine (LEV) and an anti-thyroid drug containing propylthiouracil (PTU) on the three early life stages of Xenopus laevis were evaluated with the Frog Embryo Teratogenesis Assay-Xenopus, Tadpole Toxicity Test, and Amphibian Metamorphosis Assay using biochemical and morphological markers. Tested drugs caused more effective growth retardation in stage 8 embryos than stage 46 tadpoles. Significant inhibition of biomarker enzymes has been identified in stage 46 tadpoles for both drugs. AMA test results showed that LEV-I caused progression in the developmental stage and an increase in thyroxine level in 7 days exposure and growth retardation in 21 days exposure in stage 51 tadpoles. On the other hand, increases in lactate dehydrogenase activity for both drugs in the AMA test may be due to impacted energy metabolism during sub-chronic exposure. These results also show that the sensitivity and responses of Xenopus laevis at different early developmental stages may be different when exposed to drugs.

Relationship of impaired olfactory function in ESRD to malnutrition and retained uremic molecules

BACKGROUND

Olfactory function is impaired in patients with end-stage renal disease (ESRD) and may contribute to uremic anorexia. Only limited correlations of olfactory function and nutritional status were reported. This study examines the relationship of impaired olfactory function to malnutrition and levels of the retained uremic solutes monomethylamine, ethylamine, indoxyl sulfate, and P-cresol sulfate.

STUDY DESIGN

Cross-sectional observational study.

SETTING & PARTICIPANTS

31 stable maintenance hemodialysis patients from an urban outpatient dialysis unit and 18 people with normal renal function participated.

PREDICTOR

Nutritional status assigned by using Subjective Global Assessment (SGA) score; SGA score of 7 indicates normal nutritional status; SGA score of 5 to 6, mild malnutrition; and SGA score of 3 to 4, moderate malnutrition.

OUTCOMES & MEASUREMENTS

The primary outcome is olfactory function, assessed using the University of Pennsylvania Smell Identification Test. Levels of retained uremic solutes were measured from a predialysis serum sample. Demographic data and laboratory values for nutritional status, adequacy of dialysis, and inflammation were collected.

RESULTS

Mean smell scores were 34.9 +/- 1.4 for controls, 33.5 +/- 3.3 for patients with SGA score of 7, 28.3 +/- 5.8 for patients with SGA score of 5 to 6, and 27.9 +/- 4.4 for patients with SGA score of 3 to 4 (P < 0.001 comparing healthy patients with all patients with ESRD). There was no difference in mean smell scores for healthy controls and patients with SGA score of 7. However, patients with lower smell scores had significantly lower SGA scores (P = 0.02) and higher C-reactive protein levels (P = 0.02). Neither smell score nor nutritional status was associated with levels of retained uremic solutes.

LIMITATIONS

Small sample size, only cross-sectional associations can be described.

CONCLUSIONS

Our results suggest an association between poor nutritional status and impaired olfactory function in patients with ESRD. Additional research is needed to discover the uremic toxins mediating these processes.

Impact of neonatal hypothyroidism on reproduction in the male hamster, Mesocricetus auratus

Thyroid hormones play an important role in brain development. In the present study, we examined the influence of transient postnatal hypothyroidism on reproductive neuroendocrine and behavioral outcomes in the male Syrian (golden) hamster. Hamster pups were rendered hypothyroid following exposure to the goitrogen, 6-n-propyl-2-thiouracil (PTU), between postnatal (PN) day 0 (birth) and PN25 (weaning). By 15 days after cessation of PTU, exposure (PN40) serum thyroxine levels had returned to control levels. The testes of treated males were approximately 30% heavier than controls and daily sperm production was increased by 73%. Immunocytochemistry for GnRH revealed that the total number of GnRH neurons did not vary between groups; however, a shift in the distribution of GnRH neurons was observed in treated males such that more GnRH immunoreactive neurons were found in the caudal portion of their normal distribution. The shift in GnRH distribution was associated with a significant reduction (40-50%) in pituitary gonadotropin secretion. Behaviorally, treated males took significantly longer to investigate the anogenital region and then mount a receptive female. A corresponding reduction in the total number of anogenital investigations and mounts was observed. This difference between treated males and controls was reduced, but not eliminated, over successive trials and by the third trial the number of intromission was similar between treated and control males. We conclude that the full complement of adult reproductive functions observed in the male golden hamster requires thyroid hormones during the early postnatal period. The severity of the effects induced by early hypothyroidism in this species varies from transient to permanent, depending on the endpoint.

Localization and characterization of glutathione-s-transferase isozymes alpha, mu, and pi within the mouse vomeronasal organ

The nasal cavity of vertebrates contains a variety of xenobiotic metabolizing enzymes that possess a broad range of substrate specificity ranging from metabolism of drugs, carcinogens, and steroid hormones, to dietary components and environmental pollutants. This investigation sought to localize the cellular expression and distribution of glutathione-s-transferase (GST) alpha, mu, and pi detoxifying enzymes, and to study GST activity toward different substrates in the mouse vomeronasal organ (VNO). Immunohistochemistry was used to identify GST alpha, mu and pi in the non-sensory and sensory layer of the VNO. Western blot analysis of cytosolic proteins revealed a qualitatively higher enzyme expression of GST alpha and mu in the main olfactory tissue (OE) in comparison to VNO tissue, whereas the GST pi isozyme was equally expressed in both. Total GST metabolism of 1-chloro-2, 4-dinitrobenzene (CDNB) revealed a higher activity level in the OE when compared to the VNO. In contrast, thin-layer chromatographic analysis of GST conjugation of the odorant, trans-2-hexenal (t-hex) (10 mM) showed more conjugate formed per unit protein in the VNO than the OE. The analysis of GST expression and enzyme activity within the VNO parallels the reported localization of phase I metabolizing enzymes and suggests that GST isozymes play independent roles that characterize multiple processes within VNO chemosensitivity.