Thyroid Hormone Signalling Genes Are Regulated by Photoperiod in the Hypothalamus of F344 Rats
Figure 6
Effects of melatonin, photosuppression and photoinduction on thyroid hormone signalling genes.
(A–D) Graphs are results of in situ hybridizations that show effects of SD10∶14 (SD) and melatonin injection into LD14∶10 (LD + mel) on TSHβ, Dio2, Dio3 and Oatp1c1 levels of gene expression respectively, compared to LD14∶10 (LD) at 3d and 14d time points. TSHβ, Dio2 and Oatp1c1 mRNA levels are suppressed by melatonin injection after 3d (TSHβ p = 0.015, Dio2 and Oatp1c1, p<0.001) and suppressed further by 14d (TSHβ, Dio2 and OATP1c1, all p<0.001). Dio3 in contrast was induced by melatonin injection after 3d (p<0.001) and by both melatonin and SD10∶14 after 14d (p<0.001). (E–H) Graphs show the effects of transfer of rats from SD10∶14 to LD14∶10 on gene expression levels of TSHβ, Dio2, Dio3 and Oatp1c1 respectively, after 3 and 14d. TSHβ, Dio2 and Oatp1c1 gene expression are significantly induced whilst Dio3 is inhibited at 3d (TSHβ, Dio2 and Oatp1c, p<0.001; Dio3 p<0.015). For Dio2, Oatp1c1 and Dio3, these responses were sustained at 14d (Dio2 and OATP1c, p<0.001; Dio3 p<0.01) whilst the magnitude of the response for TSHβwas further increased by 14d (TSHβ p<0.001). Bars with different letters are significantly different. Data are mean ± SE.