In vitro labeling and gold activation autoradiography were used to determine the [3H]thymidine ([3H]TdR)-labeling indices and DNA synthesis times for C3H/He spontaneous mammary tumors. Three variations of the [3H]TdR, [14C]thymidine ([14C]TdR) double-labeling method, together with double-emulsion autoradiography, were used to determine the DNA synthesis times (Ts). Tumors labeled totally in vivo (in vivo-in vivo method) and tumors labeled with [3H]TdR/n vivo and subsequently labeled with [14C]TdR in vitro showed similar Tsvalues. DNA synthesis times for tumors determined totally in vitro by double labeling (in vitro-in vitro method) were significantly longer than those observed in vivo; however, identical samples subjected to Hypaque-Ficoll gradient separation after double labeling showed 7S’s similar to those found in vivo. Furthermore, the interval between [3H]TdR and [14C]TdR administration had no effect on Tsestimates in vitro. Gold activation autoradiography was used in the present experiments to reduce autoradiographic exposure times. This method, together with in vitro labeling, permits [3H]TdR labeling index and Tsdeterminations after 6-hr and 7-day exposures, respectively.
|Original language||English (US)|
|Number of pages||6|
|State||Published - May 1976|
ASJC Scopus subject areas
- Cancer Research