CHANGES IN P2Y(1) NUCLEOTIDE RECEPTOR ACTIVITY DURING THE DEVELOPMENTOF RAT SALIVARY-GLANDS

Experiments that used dispersed salivary gland cells from 1-day-old ra ts indicated the presence of the P2Y nucleotide receptor subtype, P2Y( 1), based on the agonist potency profile for mobilization of intracell ular free Ca2+ [2-methylthio-ATP > ADP > adenosine 5'-O-(2-thiodiphosp hate) > ATP, with UTP ineffective] and sequence analysis of reverse tr anscription-polymerase chain reaction (RT-PCR) products obtained with P2Y(1) receptor-specific primers. P2Y(1) receptor activity appears to be developmentally regulated, since Ca2+ mobilization in response to t he P2Y(1)-selective agonist, 2-methylthio-ATP, decreased as animal age increased, with the maximal response of 129 +/- 23 nM obtained in 1-d ay-old animals, decreasing to 30 +/- 3 nM in 4-wk-old animals. However , the abundance of P2Y(1) receptor mRNA, assessed by semiquantitative RT-PCR, did not change over this time period, suggesting that receptor activity is regulated by some mechanism other than changes in steady- state levels of P2Y(1) receptor mRNA. These findings indicate that fun ctional P2Y(1) nucleotide receptors are expressed in immature salivary glands and that receptor activity decreases as the glands mature, sug gesting that P2Y(1) receptors may have an important role during saliva ry gland development.