No distinction was made among the 5 transgenic lines lines carrying from 1-2 to 230-240 copies of the same construct; the authors state there were no significant differences among them, whether or not results were normalized to copy number. It was noted that baseline luciferase expression varied inversely with transgene copy number. Mean basal luciferase activities in heart, skeletal muscle and adipose tissue of 4 to 5-week old transgenic mice were 4- to 38-fold higher than in tissues of mice bearing transgenes containing 254 base pairs of the HK2 promoter. Insulin induction in 5 to 6-week old transgenic mice by 4 consecutive glucose injections did not significantly increase luciferase activity in heart or skeletal muscle.