Synthesized prosequences from insulin.

Studies of the cellular effects of C-peptide have shown that it binds specifically in a nanomolar concentration range to a G-protein coupled membrane receptor, with subsequent activation of Ca²⁺-dependent intracellular signaling pathways. This resulted in stimulation of both Na⁺-K⁺-ATPase, and endothelial nitric oxide synthase activities. Administration of C-peptide to streptozotocin induced diabetic rats elicited a substantial increase in whole-body glucose turnover.