Glutamine synthetase in cultured whole retinas from the embryonic chick. Role of protein and RNA syntheses in 4 degrees C storage enhancement.
Glutamine synthetase (GS) activity is enhanced in cultured whole retinas when a 72 h incubation at 37 degrees C is preceded by storage at 4 degrees C for 2-24 h. This enhancement occurs even in the absence of glucocorticoids and is maximal in retinas from 11 to 14 d embryos. In comparison, cortisol-induced increases in retinal GS activity at 37 degrees C are optimal in retinas from 8 to 12 d embryos. This study, using cycloheximide (an inhibitor of protein synthesis) and cordycepin (an inhibitor of RNA synthesis), indicates that both protein and RNA synthesis are required for the 4 degrees C storage enhancement of GS activity. The necessary RNA synthesis occurs within the first 48 h following transfer to 37 degrees C and does not require concomitant protein synthesis. Uridine uptake, but not incorporation into trichloroacetic acid-precipitable material, is increased by initial 4 degrees C storage when compared with whole retina controls incubated at 37 degrees C for the total time. In contrast, both uptake and incorporation of amino acids are increased in 4 degrees C-stored retinas for as long as 72 h subsequent to transfer from 4 to 37 degrees C. This suggests that enhancement GS activity may arise from a combination of elevated general protein synthesis and specific messenger-RNA synthesis following 4 degrees C storage.
D000818:Animals; D002642:Chick Embryo; D003080:Cold Temperature; D046508:Culture Techniques; D003513:Cycloheximide / Q000494:pharmacology; D003839:Deoxyadenosines / Q000494:pharmacology; D005974:Glutamate-Ammonia Ligase / Q000096:biosynthesis / Q000378:metabolism*; D006854:Hydrocortisone / Q000494:pharmacology; D007700:Kinetics; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012160:Retina / Q000201:enzymology*; D013997:Time Factors
D003839:Deoxyadenosines; D012333:RNA, Messenger; D003513:Cycloheximide; D005974:Glutamate-Ammonia Ligase; D006854:Hydrocortisone