Systemic thyroid hormone is necessary and sufficient to induce ultraviolet-sensitive cone loss in the juvenile rainbow trout retina

J C Raine; A B Coffin; C W Hawryshyn

doi:10.1242/jeb.036301

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Systemic thyroid hormone is necessary and sufficient to induce ultraviolet-sensitive cone loss in the juvenile rainbow trout retina

Journal article

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Systemic thyroid hormone is necessary and sufficient to induce ultraviolet-sensitive cone loss in the juvenile rainbow trout retina

J C Raine, A B Coffin and C W Hawryshyn

Journal of experimental biology, Vol.213(3), pp.493-501

02/01/2010

DOI: https://doi.org/10.1242/jeb.036301

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https://hdl.handle.net/2376/107392

PMID: 20086135

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Abstract

Immunohistochemistry

Oncorhynchus mykiss - metabolism

Retinal Cone Photoreceptor Cells - radiation effects

Propylthiouracil - administration & dosage

Thyroxine - administration & dosage

Aging - drug effects

Fish Proteins - metabolism

Thyroxine - blood

Aging - radiation effects

Reverse Transcriptase Polymerase Chain Reaction

Oncorhynchus mykiss - blood

Gene Expression Regulation - drug effects

Propylthiouracil - pharmacology

Fish Proteins - genetics

Animals

Ultraviolet Rays

Thyroid Hormones - metabolism

Retinal Cone Photoreceptor Cells - pathology

Gene Expression Regulation - radiation effects

Retinal Cone Photoreceptor Cells - drug effects

Retinal Cone Photoreceptor Cells - metabolism

Oncorhynchus mykiss - anatomy & histology

Thyroxine - pharmacology

Aging - metabolism

Rainbow trout possess ultraviolet-sensitive (UVS) cones in their retina that degenerate naturally during development. This phenomenon can be induced with exogenous thyroxine [T4, a thyroid hormone (TH)] treatment. However, the previous T4 exposure experiments employed static water immersion; a method that could introduce confounding stress effects on the fish. Because of this, it was uncertain if T4 alone was sufficient to induce retinal changes or if stress-related hormones were also necessary to initiate this process. Furthermore, it was unclear whether endogenous T4 was the factor responsible for initiating natural UVS cone loss during development. The current study examined the role of systemic T4 on the juvenile rainbow trout retina using a slow-release implant. Exogenous T4 treatment resulted in SWS1 opsin downregulation and UVS cone loss after four weeks of exposure, signifying that T4 is sufficient to induce this process. Blocking endogenous T4 production with propylthiouracil (PTU, an anti-thyroid agent) attenuated SWS1 downregulation and UVS cone loss in the retina of naturally developing rainbow trout, suggesting that endogenous T4 is necessary to initiate retinal remodelling during development. Quantitative real-time RT-PCR analysis demonstrated that several TH-regulating components are expressed in the trout retina, and that expression levels of the TH receptor isoform TRbeta and the type 2 deiodinase (D2) change with T4 treatment. This suggests that T4 may act directly on the retina to induce UVS cone loss. Taken together, these results demonstrate that systemic TH is necessary and sufficient to induce SWS1 opsin downregulation and UVS cone loss in the retina of juvenile rainbow trout.

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Title: Systemic thyroid hormone is necessary and sufficient to induce ultraviolet-sensitive cone loss in the juvenile rainbow trout retina
Creators: J C Raine - Department of Biology, Queen's University, Kingston, Ontario, Canada, K7L 3N6
A B Coffin
C W Hawryshyn
Publication Details: Journal of experimental biology, Vol.213(3), pp.493-501
Academic Unit: Integrative Physiology and Neuroscience, Department of
Publisher: England
Identifiers: 99900547020701842
Language: English
Resource Type: Journal article