Coordination of ribosome content and polysome formation during estradiol stimulation of vitellogenin synthesis in immature male chick livers.

Publisher Website
Google Scholar
Abstract
To elucidate the mechanisms by which protein synthesis is affected by estradiol, cockerel liver polysomal profiles were characterized during hormone induction and withdrawal. A method is described for isolating intact polysomes which results in preparations that are stable even after storage in solution at 10.degree. for 16 h. In addition, the procedure eliminates the necessity for starving animals prior to experiments. Recovery of radioactive polysomes indicated that yield is about 90% and that the polysomal preparations appear to represent polysome distribution in vivo. Using this approach estradiol injection stimulates ribosome content 6-fold and formation of polysomes is coincident with the induction of vitellogenin synthesis. The size and number of polysomes increase and decrease in a coordinated fashion with the rate of vitellogenin synthesis. The kinetics of ribosome synthesis and the fact that at least 80% of the newly synthesized ribosomes are directly recruited into polysomes indicate that ribosomes might be limiting the rate of protein synthesis during the stimulatory phase of the hormone cycle.