The oral administration of sodium fluoride (NaF) (40 mumol/100 body weight [bw]) to fasting rats produced an immediate fall in insulin levels and the consequent increase in glycemia. These phenomena were observed with plasma fluoride concentrations 5-15 microM. Glycemia and insulin returned to normal levels within 4-5 hours, together with the washing out of fluoride from plasma and soft tissues. The insulin secretion of isolated Langerhans islets, perifused with solutions containing 5, 10, or 20 microM fluoride, was found to be significantly inhibited as a function of fluoride levels, both with basal and stimulatory concentrations of glucose. One hour after the intake of 60 mg of NaF, fasting human volunteers showed increased fluoride (5-15 microM) together with a significant fall of plasma insulin levels.

No abstract

Rats fed a bicarbonate-enriched diet become alkalotic during their feeding period (ca. 10 h/day). Alkalosis produced a significant reduction in the plasmatic concentration of ionized calcium and increased parathyroid hormone secretion confirmed by concurrent hypophosphatemia and increased urinary excretion of cAMP. Three weeks of treatment produced, however, a significant reduction of bone Ca resorption. The increased endogenous fecal excretion of calcium counteracted the enhancement of true calcium absorption. No significant change in the skeletal calcium mass was observed. Thyroparathyroidectomized rats fed the alkaline diet reduced further their rate of bone Ca resorption and increased significantly their skeletal calcium mass.