Uridine kinase activities in developing, adult and neoplastic rat tissues

Abstract

Uridine kinase activities were found chiefly in the soluble fractions of rat tissues. In normal adults the activities ranged from 13 munits/g in skeletal muscle to 178 munits/g in colon. Enzyme activities in several rat neoplasms were significantly higher (e.g. in a fibrosarcoma, mammary carcinoma, renal carcinoma, pancreatic carcinoma and lymphocytic lymphoma, but not in a fast-growing Morris hepatoma). The activities were not related to tumour growth rates or sizes. In normal foetal liver, lung, brain, heart and kidney, uridine kinase concentrations equalled or exceeded those in the adult homologous tissue, but maximal activities in liver were reached 3--5 days post partum. In suckling rats the intestinal activity decreased substantially immediately after birth and normally did not rise again until late in the third postnatal week. Premature upsurges could be evoked by an injection of cortisol or by starvation of the pups overnight. Pancreatic activity was absent from 1-day-old rats, and only about 5% of the adult activity was reached by day 20; adult activities were attained rapidly after weaning. In pancreas, precocious formation or uridine kinase was elicited by overnight starvation of 2-week-old rats.

Arginine metabolism: nitric oxide and beyond

“…Glucocorticoids precociously induce activities of several of the enzymes in the intestines of immature animals [98][99][100][101], indicating that these hormones probably play a role in the developmental maturation of this pathway, as is the case for many other developmentally regulated pathways in this organ [102]. This may explain why dexamethasone increases plasma concentrations of ornithine, citrulline and arginine in pre-term infants [103].…”

Substrate specificity and phosphorylation of antiviral and anticancer nucleoside analogues by human deoxyribonucleoside kinases and ribonucleoside kinases

“…UCK activity demonstrates no close correlation with cell proliferation (Sköld, 1960b;Weichsel et al, 1972). UCKs are widely distributed and have been purified from mammalian liver, lung, brain, heart, kidney, pancreas, spleen, thymus, bone marrow, testis, skeletal muscle, and small intestine (Herzfeld & Raper, 1979;Shen et al, 1998). Mouse UCK1 mRNA has previously been shown to be expressed in brain tissue (Ropp & Traut, 1996) and human UCK2 mRNA in human testis (Ozaki et al, 1996).…”

The Ontogeny of Thymidine Kinase in Tissues of Man and Rat

“…The high hepatic activities in the early postnatal period represent a considerable concentration of the enzyme in the cytosol because at that time the amount of cytoplasm per hepatocyte is still small (30% of that in the adult) (16). The elevated neonatal hepatic thymidine kinase activity coincided with that of uridine kinase (18) and was independent of the conceptual age of the rat (Table 2); it occurred equally in prematurely and normally delivered fetuses. Hepatic thymidine kinase appeared to be regulated sequentially by thyroxine (which lost its capacity to delay the normal drop after birth) and cortisol which partially accelerated the normal decrease in fetal liver and arrested thymidine kinase activity almost completely after birth (Table 3; Ref.…”

“…impermanent neonatal declines [e.g., uridine kinase (EC 2.7.1.48) (18) and pyrroline-5-carboxylate reductase (EC 1.5.1.2) (20)] are re-elicited during this quiescent period by an injection of cortisol or an 18-hr period of starvation (18,20). Neither treatment evoked changed thymidine kinase levels in liver or intestine of the same rats.…”