Effect of a Low Calcium Diet on the Levels of Protein Kinases Activity in Rat Parotid Glands

Abstract

The adult human body contains approximately 1kg of calcium (Ca), 99% of which is stored in bones and teeth as hydroxyapatite crystals . Although the Ca in bone appears to be in a static condition , it can be mobilized into the blood when necessary. The mobilization of Ca plays an important physiological role in many processes including hormone secretion , muscle constriction, and blood coagulation. Previous studies have shown that Ca also plays an important role in bone tissue formation, and that a diet deficient in this element adversely affects the growth and development of the jaw bone1). Therefore, it is natural to suspect that consuming a Ca-deficient diet will lead to dysfunction in the oral cavity. Although extensive studies on the effect of Ca on bones have been reported, relatively little is known about the effect of a protein-deficient diet2) or Cadeficient diet3,4) on salivary gland function. The proteins in acinar cells undergo three processes, synthesis, packaging, and storage and release. Each process is regulated by phosphorylation, a protein tyrosine kinase (PTK) and cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA)5-7). Therefore, cAMP stimulates the transcription of genes encoding salivary proteins. cAMP also stimulates post-translational modification such as glycosylation. Finally, cAMP stimulates exocytosis. Thus, an increase in the level of cAMP within a cell stimulates every step involved in protein secretion. In addition to PKA, acinar cells contain numerous other protein kinases including protein kinase C (PKC), that are involved in different aspects of protein synthesis and release6,7).