Insulin-induced hypoglycemia decreases uptake of 2-[F-18]fluoro-2-deoxy-D-glucose into experimental mammary carcinoma.
OBJECTIVE
To determine, in an animal study, whether insulin-induced hypoglycemia enhances tumor uptake of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) in vivo.


METHODS
Rat mammary tumors were established subcutaneously in Lewis rats. When the tumor was 1-2 cm in diameter, rats were fasted overnight and divided into two groups: control rats (n = 5) that received saline and hypoglycemic rats (n = 5) that received insulin. After 30 minutes, FDG (200 microCi [7.4 MBq]) was given intravenously. One hour after FDG injection (ie, at sacrifice), plasma glucose and insulin levels were measured and F-18 activity in tumor and normal tissues was determined.


RESULTS
Mean glucose level was 32.8 mg/dL (1.8 mmol/L) and mean insulin level was 2,831.1 microU/mL (20,315 pmol/L) in the hypoglycemic animals. As compared with the control value, mean FDG uptake in tumor (percentage of injected dose [per gram of tissue] per kilogram of animal weight) significantly decreased with hypoglycemia (0.117 vs 0.331, P = .0001). Mean FDG uptake in the heart and muscle was 9.75 and 5.18 times higher, respectively, in the hypoglycemic rats (P = .0001). Thus, the tumor/muscle uptake ratio was significantly reduced with hypoglycemia (2.15 vs 31.62, P = .0002).


CONCLUSIONS
Tumor targeting with FDG is impaired, not enhanced, by insulin-induced hypoglycemia.
Torizuka
T
T
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0028, USA.
Fisher
S J
SJ
Wahl
R L
RL
D000818:Animals; D003847:Deoxyglucose / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics*; D019788:Fluorodeoxyglucose F18; D007003:Hypoglycemia / Q000139:chemically induced / Q000150:complications*; D007328:Insulin; D008325:Mammary Neoplasms, Experimental / Q000097:blood / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew
D005462:Fluorine Radioisotopes; D007328:Insulin; D019788:Fluorodeoxyglucose F18; D003847:Deoxyglucose