RELATIVE ACTIVITIES OF THYMIDYLATE SYNTHETASE AND THYMIDINE KINASE IN RAT-TISSUES

  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (3) , 744-750
Abstract
The activities of thymidylate synthetase and thymidine kinase were compared in tissues of normal (adult and developing), cortisol-injected and tumor-bearing rats to determine whether the activities of these 2 enzymes, which catalyze reactions leading to the same metabolic intermediate, changed proportionately, reciprocally or independently under different physiological conditions. Both enzymes had high activities in fetal tissues. Thymidine kinase concentrations decreased shortly before or immediately after birth; in several tissues, transient postnatal peaks in thymidine kinase activities appeared within the 1st 3 wk after birth. Thymidylate synthetase activities declined gradually after parturition and showed no significant postnatal rises. In sucklings given injections of cortisol, thymidine kinase activities were reduced substantially in 8 tissues while thymidylate synthetase decreased only in lung and thymus of 11 day old rats. In tumor-bearing rats, thymidine kinase activity increased dramatically in spleen, whereas thymidylate synthetase activities only doubled. In host liver, rises in thymidine kinase activities were not always matched by increases in thymidylate synthetase. In the tumors, both activities were higher than in most normal adult tissues. Thymidylate synthetase and thymidine kinase were closely correlated in tissues of untreated animals. The Spearman rank correlation coefficient for 112 tissues was 0.895, while the correlation coefficient between the standard scores of the activities was 0.839. The activities of the 2 enzymes did not appear to be reciprical or compensatory during normal differentiation or during dedifferentiation associated with tumor bearing, but their potentials for activity were independent of each other.