Retinal growth hormone in the chick embryo

Area of Science:

• Ophthalmology
• Endocrinology
• Developmental Biology

Background:

• The presence of growth hormone (GH) and its messenger RNA (mRNA) in embryonic chick eyes remains controversial.
• Previous studies have yielded conflicting results regarding ocular GH expression.

Purpose of the Study:

• To investigate the presence and localization of GH and GH mRNA in embryonic chick neural retinas.
• To determine the functional significance of GH in retinal development and ocular function.

Main Methods:

• RT-PCR was used to generate GH cDNAs from neural retina mRNA.
• Immunoreactivity for GH was assessed using specific antibodies.
• In situ hybridization localized GH mRNA.
• Cultured embryonic retinas were treated with GH to measure IGF-1 mRNA levels.

Main Results:

• Full-length GH cDNAs and GH mRNA were detected in embryonic chick neural retinas.
• GH immunoreactivity was primarily associated with 15 and 16 kDa proteins, with minimal monomeric GH.
• GH staining was abundant in retinal ganglion cells (RGCs) and surrounding areas.
• GH treatment significantly increased IGF-1 mRNA in cultured embryonic retinas, indicating GH action.

Conclusions:

• This study confirms the presence of GH mRNA and specific GH protein forms in the embryonic chick neural retina.
• GH is localized to RGCs and exhibits biological activity within the retina.
• These findings suggest previously unrecognized roles for GH in embryonic eye development and function.