P2Y1 Receptor Activation Enhances the Rate of Rat Pinealocyte-Induced Extracellular Acidification via a Calcium-Dependent Mechanism

Pineal gland G-protein coupled P2Y₁ receptors potentiate noradrenaline-induced N′-acetylserotonin production, a long term response which occurs after 5 h incubation. In the current study we show that a short-term effect of stimulation of P2Y₁ receptors is the increase in extracellular acidification rate (ECAR), which is mediated by an increase in intracellular calcium concentration ([Ca²⁺]_i). The pD₂ values for ATP (3.06 ± 0.12)-induced ECAR increase was significantly smaller (p < 0.01) than that for ADP (3.64 ± 0.18), 2MeSATP (3.56 ± 0.02) and 2MeSADP (3.65 ± 0.13). The selective P2Y₁ receptor antagonists A3′P-5′P and A3′P-5′PS inhibited the increase in ECAR-induced by ADP. Clamping [Ca²⁺]_i with BAPTA (30 and 50 µmol/l) led to inhibition of ADP-induced increase in ECAR. Agonist and antagonist data indicate P2Y₁ activation leads to a [Ca²⁺]_i-dependent acidification of the extracellular medium.