Aberrant sodium absorption has been linked to the development of hypertension in both renal disease and diabetes. Efficient absorption depends on co-ordination of cellular activity across the entire epithelium via cell-to-cell coupling. In the current study we have utilized a model human collecting duct cell line (HCD) to assess the role of connexin-43 (Cx-43) mediated gap-junctions in the transfer of intracellular calcium transients within coupled cell clusters. HCD-cells express Cx-43 mRNA and protein, as well as that for the mechano-sensitive transient receptor potential receptor (TRPV4). Mechanical stimulation of individual cells within a cluster evoked a transient rise in cytosolic calcium ([Ca²⁺]_i) that propagated between cells via a heptanol-sensitive mechanism. The rise in [Ca²⁺]_i was dependent on both store release and Ca²⁺-influx pathways. Lucifer Yellow dye transfer and Cx-43 knockdown experiments confirmed direct cell-to-cell communication. Application of the Ca²⁺-ionophore ionomycin, or an increase in glucose (5-to-25mM), produced a time-dependent (48 hours) increase in Cx-43 protein expression. The transmission rate of touch-evoked Ca²⁺-transients between coupled cells was accelerated following exposure to high glucose, providing a functional correlate to increased Cx-43 expression. These data suggest a pivotal role for Cx-43 mediated gap-junctions in the synchronization of activity between cells of the human collecting duct in response to stimuli that mimic osmotic and physical changes. Cx-43 expression and cell-to-cell communication increased in response to high glucose and may protect the collecting duct from renal damage associated with more established diabetic nephropathy.