Arginine Vasopressin (AVP) Glucose-Dependently Modulates Pancreatic Alpha and Beta Cell Activity via `V1b` Receptors

Arginine vasopressin (AVP) is a crucial hormone primarily known for its roles in fluid balance, osmotic regulation, and vascular tone. While its influence on pancreatic α and β cell function has been observed, the precise mechanisms, especially concerning its interaction with plasma glucose levels, remain incompletely understood. This knowledge gap is particularly relevant in the context of diabetes, where osmotic and volume challenges from hyper- and hypoglycemia can significantly impair effective hormonal regulation of metabolism. Understanding AVP's role in glucose-dependent hormone release could unlock novel therapeutic strategies for managing glycemic control.

Researchers investigated the effects of Arginine Vasopressin (AVP) and synthetic peptide receptor agonists/antagonists on α and β cells within pancreatic tissue slices. The primary methodology involved live confocal Ca2+ imaging to monitor cellular activity. The study explored AVP's effects under varying glucose concentrations, both alone and in combination with physiologically or pharmacologically increased cAMP levels. They also assessed the concentration dependence of AVP's effects and utilized specific receptor antagonists to identify the AVP receptor subtypes involved in modulating islet cell function.

Arginine vasopressin (AVP) demonstrated distinct glucose-dependent effects on both alpha and beta pancreatic islet cells. At low glucose concentrations, AVP, when combined with increased cAMP levels (physiological or pharmacological), selectively activated alpha cells without significantly affecting beta cell activity. In contrast, at higher glucose concentrations and pharmacologically elevated cAMP levels, physiological levels of AVP enhanced beta cell activity, leading to increased Ca2+ oscillations and subsequent insulin release. A significant finding was the bell-shaped concentration dependence of AVP's effects in both cell types, where lower AVP concentrations stimulated hormone release, while higher concentrations led to diminished responses, consistent with inositol trisphosphate receptor (IP3R) activation and inactivation properties. > Furthermore, the study definitively showed that AVP acts primarily through V1b receptors in beta cells, with no involvement of V1a, V2, or oxytocin receptors in these observed effects.