Abstract
Abstract The pyrimidine deoxyribonucleoside kinase activities were very low in the normal mouse parotid gland, while uridine kinase activity was high. Isoproterenol administration increased uridine, deoxycytidine, and thymidine kinase activities 2-, 10-, and 30-fold, the enzymes reaching maximum activity at 12 to 14, 27, and 30 hours after isoproterenol injection, respectively. DNA synthesis was maximal at 27 hours. In control glands 25% of the deoxycytidine and thymidine kinase activities was present in a nuclear fraction and 40% of the uridine kinase activity in the microsomal fraction. Most of the remainder of their activities was present in the high speed supernatant fraction. After isoproterenol injection the activities of these enzymes in the nuclear, mitochondrial, and microsomal fractions changed only slightly, while 97% of the increased activities was present in the cytosol fraction. Sedimentation of crude homogenates on sucrose gradients showed that the nuclear and cytoplasmic forms of the deoxyribonucleoside kinases had the same molecular weights, being 65,000 for deoxycytidine kinase and 70,000 for thymidine kinase. Isoproterenol produced no change in the sedimentation characteristics of deoxycytidine kinase, but three new thymidine kinase species with molecular weights of 55,000, 95,000, and 130,000 were present under varying conditions.
Highlights
In control glands 25 % of the deoxycytidine and thymidine kinase activities was present in a nuclear fraction and 40% of the uridine kinase activity in the microsomal fraction
The animals were killed by ceriical dislocation and the parotid glands removed and chilled in ice-cold Medium A
The homogenate was passed through two layers of cheesecloth and an aliquot retained for the assay of the total homogenate
Summary
The pyrimidine deoxyribonucleoside kinase activities were very low in the normal mouse parotid gland, while uridine kinase activity was high. In control glands 25 % of the deoxycytidine and thymidine kinase activities was present in a nuclear fraction and 40% of the uridine kinase activity in the microsomal fraction. A single intraperitoneal injection of isoproterenol produces, after a lag period of about 20 hours, a marked increase in DNA synthesis in the salivary glands of both rats [1] and mice [2]. This organ is the only one in rodents with the exception of the kidney [3] to respond to isoproterenol with cellular proliferation. The subcellular distribution of the pyrimidine nucleoside kinase activities in the nonstimulated mouse parotid gland and the effect of isoproterenol on both the activity and distribution of these enzymes are described
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