Purinergic Signalling (2012) 8 (Suppl 1):S61–S79 the development of drugs in order to enhance the reverse cholesterol transport [38]. Low-intensity pulsed ultrasound (LIPUS) is a noninva- sive technique used to stimulate the healing process of bone fractures. The only known molecular event involved in LIPUS treatment is the release of purines from osteoblasts. P2 receptors were pharmacologically detected in osteo- blasts. Activation was monitored by calcium mobilization which was abolished upon the addition of inhibitors of endoplasmic reticulum calcium release. Although all P2Y receptor subtypes tested were detected in indirect flow cytometry experiments using their respective Alomone Labs antibodies (Fig. 5), P2Y1 seems to have a prominent role upon LIPUS treatment as inhibitors of this receptor abolished the proliferation of osteoblasts [41]. Melanoma is a tumor originating from melanocyte. These tumors express P2Y1 and P2Y2 receptors, among others [42]. Immunocompromised mice were injected with melanoma cells, and the role of purinergic agonists on tumor size and development was examined. Following ATP administration, the tumors had a necrotic appearance. Immunohistochemistry studies using Alomone Labs anti- bodies showed that the expression of P2Y1 increased in the areas adjacent to the necrotic region, strongly suggesting that ATP can be used as a treatment for melanoma. Achondroplasia is a pathology causing dwarfism. It is caused by a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene, leading to the constitutive activation of the FGFR3 signaling pathway. In addition, the mutant form of the receptor is unable to mobilize calcium, suggesting that calcium mobilization (or lack of) plays a role in the development of the pathology. P2Y receptors have been described in chondrocytes (cells in the S69 endochondral bone growth in mammals) [43]; however, their presence and function in achondroplastic chondrocytes have been examined in the presented study [44]. Using confocal microscopy, immunoreactivity against P2Y1, P2Y2, P2Y6, and P2Y11 was detected using Alomone Labs antibodies, while that of P2Y4 was not present in achondroplastic chondrocytes. The results were also con- firmed by Western blot analysis. Treating these cells with dinucleotide polyphosphates gave rise to an increase in intracellular calcium concentrations. This effect was elim- inated (to various extents) by applying different P2 antagonists. Treating chondrocytes with FGF9, the natural ligand of FGFR3, promoted calcium mobilization which was not observed when treating achondroplastic condro- cytes with the same ligand, due to the constitutively active FGFR3 signaling cascade. However, when treating these cells with dinucleotide polyphosphates prior to FGF9 treatment, the calcium mobilization was restored by a mechanism that is yet still not understood. The study suggests that the activation of P2Y receptors may be a useful pharmacological tool to reset the modified biochem- ical process observed in achondroplasia. In the next section, we discuss the many uses of our antibodies directed against ionotropic P2X receptors. P2X receptors The P2X receptors are a family of ligand-gated, non- selective cation channels that open in response to extracel- lular ATP. In vertebrates, the family comprises seven members termed P2X1–P2X7 that share 40–50% sequence homology. The P2X receptors have a topology that includes Fig. 5 Expression of P2Y receptors in osteoblasts. Using flow cytometry analysis, P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, and P2Y13 receptors were detected in osteoblasts using their respective Alomone Labs antibodies (open histograms). Incubating the antibody with the control peptide antigen was used as a negative control (filled histograms). Adapted from reference 41 with permission of Elsevier