Existence of P2-purinoceptors on human and porcine granulosa cells.

This study examines the possible roles of extracellular purine nucleotides in regulating ovarian granulosa cell function. Using luteinized human (L-hGC) and porcine granulosa cells (PGC), we examined the effects of purine nucleotides on intracellular free Ca2+ concentrations ([Ca2+]i), and whether they have any effect on steroidogenesis and cell proliferation. L-hGC and PGC were responsive to ATP and ADP at concentrations ranging from 0.1-100 mumol/L in a dose-dependent manner. There was a difference between L-hGC and PGC in the rank orders of agonist potencies for stimulating [Ca2+]i; for L-hGC, UTP > ATP > ATP gamma s > ADP > AMPPNP >> AMP and adenosine; for PGC, 2-methylthio ADP (2-meS ADP) > ADP > ATP = ATP gamma s = UTP > AMPPNP >> AMP and adenosine. No apparent additivity between the responses elicited by UTP and the purine nucleotides (ATP and ADP) was shown in L-hGC. On the other hand, an apparent additive effect between the responses to ADP and UTP was shown on PGC. Furthermore, ATP was a competitive antagonist of the action of ADP on [Ca2+]i levels in PGC. ATP, ADP, and AMP as well as adenosine stimulated basal progesterone and estradiol secretion from L-hGC, however, UTP had no effect on steroidogenesis in L-hGC. On the other hand, purine nucleotides and UTP as well as adenosine inhibited progesterone and estradiol secretion on PGC. However, 2-meS ADP, the most potent agonist for P2T-purinoceptors, did not affect steroidogenesis in PGC. Purine nucleotides had no influence on cell proliferation of L-hGC and PGC. These results indicate the existence of P2U-purinoceptors on L-hGC and P2U- plus P2T-purinoceptors on PGC, and that the inhibitory effect of purine nucleotides on steroidogenesis in PGC is most likely due to A1-adenosine receptors and also P2U-purinoceptors.