DETERMINATION OF DEGRADATION RATES OF TRANSFER AND RIBOSOMAL RIBONUCLEIC-ACIDS IN CULTURED RAT HEPATOCYTES BY MEASURING N-6-THREONINOCARBONYLADENOSINE, DIHYDROURIDINE, AND PSEUDOURIDINE IN MEDIUM USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Modified ribonucleic acid catabolites excreted into the medium by prim ary cultures of rat hepatocytes (2.3 +/- 0.42 x 10(6) cells/dish) duri ng a 24-h cultivation period were quantified by reversed-phase high-pe rformance liquid chromatography (fmol/10(3) cells): 613 +/- 81 dihydro uridine, 46 +/- 6 N-6-threoninocarbonyladenosine, 1879 +/- 220 pseudou ridine. On the basis of these excretion rates and the average frequenc y of occurrence of these modified ribonucleosides per cytoplasmic tran sfer ribonucleic acid (residues: 2.6 dihydrouridine, 0.22 N-6-threonin ocarbonyladenosine, 3 pseudouridine) as well as per cytoplasmic riboso mal ribonucleic acid (residues: 95 pseudouridine), the degradation rat es of transfer and ribosomal ribonucleic acids were calculated. The de gradation rate of transfer ribonucleic acid (fmol/10(3) cells/24 h) wa s 236 +/- 31 (via dihydrouridine) and 211 +/- 28 (via N-6-threoninocar bonyladenosine) and that of ribosomal ribonucleic acid (fmol/10(3) cel ls/24 h) was 13.1 +/- 1.7 (via pseudouridine and N-6-threoninocarbonyl adenosine). (C) 1997 Academic Press.