Giant nucleoplasmic RNA in the switch-on of compensatory renal growth.

Heterogeneous RNA (HnRNA) (ca. 10S-70S) labeled for ten minutes with (3)H-uridine was identified by polyacrylamide-gel electrophoresis in the nucleoplasm of kidney cells. In the region >28S several discretely migrating species were present. Ten minutes after the removal of one kidney, labeled HnRNA >28S ("giant" HnRNA) in the remaining kidney began to decrease, and by 60 minutes it had fallen drastically. The presence of labeled giant HnRNA during a pulse label after uninephrectomy and its disappearance after longer labeling suggest that the decrease is a consequence of faster processing. Accelerated processing of giant HnRNA is antecedent to the increased synthesis of renal cytoplasmic RNA that follows uninephrectomy.