Presence of functional oxytocin receptors in cultured human myoblasts

In the present report, we provide for the first time evidence that functional oxytocin receptors (OTRs) are present in human myoblasts obtained from clonal cultures of postnatal satellite cells. First, binding studies performed with a non selective vasopressin (AVP) and oxytocin (OT) radioligand indicated the presence of a single class of binding sites. Second, OTR mRNA was detected by RT-PCR analysis whereas transcripts for AVP V1a, V1b or V2 receptors (V1aR, V1bR and V2R respectively) were not detected. Third, the presence of functional OTRs was evidenced by showing that agonist substances having a high affinity for the human OTR, namely OT, AVP and LThr4,Gly7]OT, increased the rate of myoblasts fusion and myotubes formation in the cultures, whereas F180, a V1aR selective agonist, and dDAVP, a V2R agonist had no significant effect on the fusion process. In addition, we show by RT-PCR and immunocytochemistry that the OT gene is expressed in cultured myoblasts. Taken together, our data suggest that OT may act as a paracririe/autocrine agent that stimulates the fusion of human myoblasts in vitro. In vivo, OT may be involved in the differentiation. of human skeletal muscle during postnatal growth, and possibly its regeneration following injury.