CHANGES IN USNRNA BIOSYNTHESIS DURING RAT-LIVER REGENERATION (VOL 131, PG 67, 1994)

Partial hepatectomy (P.H.) induces a partially synchronized growth res ponse of liver under normal regulation of growth. In this phase change s in cellular morphology, radial distribution pattern of cells and oth er biological as well as major biochemical changes are well documented [24]. Here, we have shown that the cellular content of UsnRNAs altere d during this proliferative phase as well. The level of spliceosomal U snRNAs (U1, U2, U4-U6) gradually decreased by 30-50% upto 48 hrs of P. H. followed by gradual increase to reach the normal level within one m onth of P.H. The U3 snRNA level on the other hand, was nearly equal to that in normal liver at 48 hrs of P.H. but in 24 and 72 hrs of P.H. i ts level was high (4 fold) in contrast to that in other UsnRNAs. Thus, it is clear from our data that the level of all the six UsnRNAs decre ased during 48 hrs of P.H. compared to that after first 24 hrs. This h as been correlated in the kinetics of UsnRNAs' synthesis (in terms of labelling) in isolated hepatocytes, where the rate of labelling of all the six UsnRNAs increased 20-30% in 24 hrs regenerating hepatocytes ( R.H.) followed by sharp decrease by 30-50% within next 24 hrs, compare d to that in the normal hepatocytes. But from 72 hrs onwards in R.H. t he rate of labelling of all the six UsnRNAs again increased by 30-50% (compared to that in normal hepatocytes) followed by decrease of their labelling-rate to reach the normal level in R.H. within one month of P.H. Thus, it may be concluded that the changes in UsnRNAs' level duri ng the proliferative phase of liver regeneration may be either due to the alteration in the rate of synthesis (in terms of labelling) or alo ng with it differential turn over rate; this phenomenon may have some consequences with the regenerative process of liver.