The aim of this study was to determine whether luteal cells possess functional receptors for lysophosphatidic acid (LPA). We present evidence that [3H]LPA binds to a 38-40 kDa protein in a membrane fraction prepared from luteal cells and that this phospholipid is able to induce tyrosine phosphorylation of several proteins (65-125 kDa). Furthermore, LPA upregulates forskolin- and LH/GTP-stimulated adenylyl cyclase activity by changing its Vmax. Although a pertussis toxin-sensitive G-protein has been reported to transmit the inhibitory signals between the LPA receptor and adenylyl cyclase, the observed upregulation of the enzyme activity in luteal cells is not abolished after pre-treating the cells with the toxin, suggesting that a different mechanism is operative in these cells. According to the pharmacological regulatory pattern it is suggested that the modulated adenylyl cyclase isoform is the enzyme subtype V expressed in luteal cells.
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