Changes in P2Y(1) nucleotide receptor activity during the development of rat salivary glands

Experiments that used dispersed salivary gland cells from 1-day-old rats indicated the presence of the P2Y nucleotide receptor subtype, P2Y(1), based on the agonist potency profile for mobilization of intracellular free Ca2+ [2-methylthio-ATP > ADP > adenosine 5'-O-(2-thiodiphosphate) > ATP, with UTP ineffective] and sequence analysis of reverse transcription-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 the P2Y(1)-selective agonist, 2-methylthio-ATP, decreased as animal age increased, with the maximal response of 129 +/- 23 nM obtained in 1-day-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 functional P2Y(1) nucleotide receptors are expressed in immature salivary glands and that receptor activity decreases as the glands mature, suggesting that P2Y(1) receptors may have an important role during salivary gland development.