The effects of glucocorticoids on thymidine kinase and nucleoside phosphotransferase during development of chicken embryo retina

Abstract

Thymidine kinase in chick embryo retina reaches its highest values on the B-10th day of development, then declines reaching the lowest value at hatching. The rate of DNA synthesis essentially follows this activity while, in contrast, nucleoside phosphotransferase increases progressively during development. Glucocorticoids at 5 x low6 M lower the level of thymidine kinase in isolated retinas of chick embryo. The most effective steroid was hydrocortisone. The effect was observed in retinas from 8-18-day-old chick embryo and, except on the 8th day, was always of the same magnitude. We suggest that a glucocorticoid can be the natural factor responsible for the marked fall in thymidine kinase during deveIopment. Brief periods of exposure to steriods increase nucleoside phosphotransferase activity in isolated chick embryo retinas. When the exposure was longer than 3 h this activity was also clearly decreased. We conclude that other factors are responsible for the natural increment which occurs for this activity during development. Thymidine kinaseGlucocorticoid ~eveia~men t Retina Nucleoside ~hos~hoiru~sferuse

Influence of Hydrocortisone on Chick Embryo Retina Development

“…The mixture was incubated for 15 min at 37°C and the reaction was stopped by addition of 200 PI of 10% trichloroacetic acid. Thymidylic acid (TMP) production was measured as described by Tesoriere et al (1983). Control assays without enzyme or ATP were done, and preliminary studies established that the enzyme assay was performed under conditions where thymidine kinase activity was linear with time and proportional to the amount of homogenate present.…”

“…The highest levels of enzyme activity occur on days 8-9 after fertilization, when the tissue is still engaged in rapid cell proliferation; there is then a decline as the tissue differentiates and matures (Tesoriere et al, 1983). As hydrocortisone decreases the activity of thymidine kinase in isolated retinas of chick embryos (Tesoriere et al, 1983), we thought it possible that injected glucocorticoids would also influence retinal development before the pituitary regulation of 1694 R. VENT0 ET AL.…”

“…This has been seen with the thymus of adult animals, erythropoietic cells of fetal rat liver (Greengard and Machovich, 1972), and lymphosarcoma P1798 cells (Cavanaugh and Thompson, 1983). Thymidine kinase activity vanes greatly during growth and differentiation (Machovich and Greengard, 1972;Hyndman and Zamenhof, 1978), and in developing chick retina, there is a close correlation with the rate of DNA synthesis (Tesoriere et al, 1983). The highest levels of enzyme activity occur on days 8-9 after fertilization, when the tissue is still engaged in rapid cell proliferation; there is then a decline as the tissue differentiates and matures (Tesoriere et al, 1983).…”

“…Thymidine kinase activity vanes greatly during growth and differentiation (Machovich and Greengard, 1972;Hyndman and Zamenhof, 1978), and in developing chick retina, there is a close correlation with the rate of DNA synthesis (Tesoriere et al, 1983). The highest levels of enzyme activity occur on days 8-9 after fertilization, when the tissue is still engaged in rapid cell proliferation; there is then a decline as the tissue differentiates and matures (Tesoriere et al, 1983). As hydrocortisone decreases the activity of thymidine kinase in isolated retinas of chick embryos (Tesoriere et al, 1983), we thought it possible that injected glucocorticoids would also influence retinal development before the pituitary regulation of 1694 R. VENT0 ET AL.…”