Sodium requirement in secretory processes regulated through muscarinic receptors in rat parotid glands

In rat pdrotid glands. the chohnergc stunulatlon through the rnuscaruuc receptor enhances amylase secretion dnd potdssiunl efflux [l-4] Both responses require calcluni in the extracellular medium [1.2,4] The chohnerglc effects are mlmlcked by lonophore A 23 187 which introduces Ca” into the acmar cell [5,6] and mhlblted by antagonists of Ca*+movements like lanthanum [7,7] The chohnerglc agomst stlmulates 45CaZ’ uptdke m rat parotid glands and this effect 1s also abolished by lanthanum [7,8] Therefore the pnmary event of chohnerglc stunulatlon could be Ca2+ entry mto the cell On the other hand the muscarmlc stlmulatlon also produces an increased turnover of the phosphomowtol group m phosphdtldylmosltol [7,9] However this last effect IS independent of exogenous Cd*+ and IS not mmilcked by lonophore A 23187 [5,10] By using lanthanum we have demonstrated a relatlonshlp between the phosphohpldlc effect induced by chohnerglc agonist (Independent of calcium), the Cd*+ upt‘lhe and the secretory processes (dependent on extracellular Cd”) [7] As opposed to the role of Cd*‘. the lole of Na’ IS not well hnown Chohnerglc dgomsts have been shown to enhance Na’ uptake m rat parotid glands [ 1 l] However this latter effect IS also dependent on a Cd*+ entry This work was undertahen to study the unportance of the vallatlons of NJ’ concentration gradient between extraand mtracellular medium m relation