Effect of NaF on cAMP Accumulation, cAMP-dependent Protein Kinase Activity in, and Amylase Secretion from, Rat Parotid Gland Cells

Stimulation of amylase secretion from parotid glands by beta-adrenergic agonists is mediated by the activation of adenylate cyclase and the resultant increase in cellular cAMP. Since NaF is known to increase adenylate cyclase activity and cAMP accumulation in intact cells, we investigated whether it would stimulate amylase secretion from isolated rat parotid gland cells. The results provide evidence that the addition of NaF (0.01 - 10 mmol/L) increased cAMP concentration (1.5-2.8-fold) in, and amylase secretion (16-93%) from, isolated parotid gland acinar cells. NaF was found to increase cAMP-dependent protein kinase activity ratios (51-84%) in a concentration-and time-dependent manner. The data suggest that the stimulation of amylase secretion from parotid gland cells by NaF may be mediated by an increase in the cellular cAMP concentration, which exerts its effect, at least in part, by increasing the activity of cAMP-dependent protein kinase.</jats:p

Effect of NaF on Rat Parotid Gland Amylase Activity and cAMP Concentration in vitro and in vivo

The effect of NaF on the cAMP concentration in and amylase secretion from rat parotid glands in vitro and in vivo was investigated. In vitro, NaF (0.05 to 10 mmol/1 ) was found to increase significantly amylase secretion and cAMP concentration in parotid gland slices. In vivo, male rats injected intraperitoneally with 15 mg Flkg body weight as NaF had a significantly lower glandular amylase activity and higher plasma amylase activity than did the control rats injected with 0.9% NaCl. The fluoride concentration both in the parotid gland and plasma was highest at 30 min after injection and decreased with time in the fluoride-injected group. The concentration of the parotid gland cAMP in the fluoride-injected group was significantly higher than that in the control group. On the basis of these results, it is suggested that NaF, both in vitro and in vivo, increases the cAMP concentration, which subsequently stimulates amylase secretion from rat parotid glands. </jats:p

Topical Fluorides: Effects on Physiologic and Biochemical Processes

The ingestion of fluoride from dentifrices or mouthrinses can contribute substantially to the total daily intake of the ion, even in communities that provide optimally fluoridated drinking water. It is concluded that the frequent and unsupervised use of these products by children six years of age or younger, especially those living in areas with water fluoridation, places them at risk of dental fluorosis. Recommendations to reduce the risk are presented. The use of 1.23% (12,300 ppm) APF gels, particularly in the absence of suctioning during the application and expectoration after the application, is associated with the swallowing of relatively large quantities of fluoride. The resulting increases in plasma fluoride levels may be sufficient to cause dental fluorosis, as judged by studies with laboratory animals, and a reduction in the kidney's ability to concentrate the urine, as judged by studies with both laboratory animals and humans. The epigastric distress experienced by some patients during or after APF gel applications appears to be due, at least in part, to a direct toxic effect of fluoride on the gastric mucosa. Data from studies with humans and laboratory animals indicate that there may also be associated changes in plasma and tissue cAMP levels, glucose metabolism, and salivary amylase secretion. There is an immediate need for the dissemination to the dental profession of standardized methods for gel application that will minimize the quantities of fluoride available for ingestion and systemic absorption. </jats:p