Several investigators have shown an acute administration of NaF in rats can induce a hyperglycemia. The current study was undertaken to determine if acute injections of NaF would alter the serum insulin levels since LIN et al., Horm. Metab. Res 8, 353-358, 1976 had shown that NaF could inhibit the synthesis and release of insulin from isolated pancreatic islets and that a lowering of serum insulin could result in hyperglycemia. Male Wistar rats (8 per group) were fasted for 16-24 hours prior to receiving an ip injection of NaCl (control) or NaF (0.5 to 20 mg F/kg body weight). The rats were anesthesized and blood collected by heart puncture 30 min after the injection of NaCl or NaF. The serum was analyzed for insulin (radio-immunoassay), glucose, and fluoride. There was a significant increase in serum glucose (120% increase), and serum fluoride (10 to 700 fold) 30 min after the injection of NaF. The serum insulin levels ere also significantly reduced 30 min after injection of NaF. The insulin levels were 60%, 66%, 75% and 45% of the control values after injection of 0.5, 1.6, 5, and 20 mg F/kg. The data for the first time showed that acute administration of fluoride may inhibit insulin release in 24 hr fasted rats as reflected by significantly lower serum insulin level. It is concluded that the NaF induced hyperglycemia could be due in part to the reduction of serum insulin which would decrease the uptake of glucose by muscle and adipose. It should be noted that the lowest dose of NaF (0.5 mg/kg) is in the range of fluoride ingestion observed following a topical application of APF gel. Thus it is conceivable that normal ingestion of F following an APF application could alter several metabolic processes.
This research was supported in party by a NIDR grant 04387, Grace M. Showalter Trust fund and DRTC – AM 20542.