SALIVARY GLAND SECRETORY MECHANISMS DURING NORMAL AND ALTERED FUNCTIONAL STATES

口腔的健康是由唾液分泌物维持的。公关

The health of the oral cavity is maintained by salivary secretions. The pr cipal function of salivary glands is to produce these complex fluids. We utilize n vitro dispersed cells of salivary glands to understand mechanisms controlling sal a formation. We have focused our studies on neurotransmitter regulation of secretory eve s and associated signalling mechanisms. During this reporting period the primary ocus of study continues to be muscarinic receptors (mAChRs) in rat parotid gland acinar c ls and their coupling to functional responses via specific G proteins. We have also ini ated studies of alpha-adrenergic receptors (alpha1-ARs) in these cells. In parotid cell stimulation of mAChRs results in the generation of inositol phosphates via the activati of a phosphatidylinositol 4,5-bisphosphate specific phospholipase C. Subsequent this response leads to the elevation of cytosolic Ca2+ levels and fluid secretio Additionally, mAChRs can mediate the inhibition of agonist induced cAMP for tion. We have characterized the binding of a subtype non-selective antagonist (quinu idinyl benzilate, QNB) to mAChRs in intact rat parotid cells. Specific binding is aturable, time- and temperature-dependent (Bmax approximately 80 fmol/mg protein; Kd proximately 100 pM). Also, we have assessed the relationship between mAChR occupancy a second messenger formation, determining that a moderate population (approximately -40%) of spare receptors exist for inositol trisphosphate (IP3) formation. We previ sly reported that rat parotid M3-mAChRs couple to two different signal transducing G pro ins. This year we determined the nucleotide sequence encoding the region of this rece or gene involved in G-protein coupling and we observed that it is virtually identic to other reported 3 sequences. Thus, the mAChR itself is unlikely to be responsibl for the divergent coupling. Additionally, we have shown that the alpha1-adrenergic eceptor subtype involved in the fluid secretory response is alpha1A.