Thyrotropin-releasing hormone-like material in the rat retina: changes due to environmental lighting.

Abstract

Material reacting with an antibody to thyrotropin-releasing hormone (TRH) was present in the rat retina. The compound present in the retina cochromatographed with authentic TRH and most of its activity was lost when incubated with pyroglututmate aminopeptidase (L-pyroglutamyl-peptide hydrolase, EC 3.4.11.8), an enzyme that degrades TRH. The TRH-like activity in the rat retina was low during the night and high during the day. There was a 4 h lag period after the lights were turned on before peak TRH levels were attained. A decrease in TRH was seen after 2 h of darkness and level of TRH was lowest after 4 h of darkness. Retinal TRH is elevated by environmental lighting regardless of the time of the day. TRH may be involved in retinal photoreceptive mechanisms.