Figure 1.

Time course and log dose-response of doxycycline effect on glucokinase level in INS-r3-GK27 cells. (A) Cells were cultured in medium containing 2.5 mM glucose and 1,000 ng/ml doxycycline. They were harvested at the indicated times for enzyme assay of glucokinase activity. (B) Cells were cultured with the indicated doses of doxycycline for 48 h. Cell extracts were subjected to SDS/PAGE in a 9% acrylamide gel, transferred to nitrocellulose, and immunoblotted with an antiserum to glucokinase. Lanes were loaded with 10 μg of soluble protein, except the three rightmost lanes, which received (from right) 0.83, 2.5, and 5 μg of protein, respectively, from cells cultured with 1,000 ng of doxycycline per ml. (C) Linear regression analysis of glucokinase activity assayed in the same samples, as a function of densitometer units of glucokinase band in the immunoblot.