The blood supply of the islets of Langerhans in the Mongolian gerbil.

Ink injection studies and point counting have been used to follow and quantify the development of vascularity in the islets of Langerhans of the Mongolian gerbil. Vascularization is essentially a postnatal event in this species. Initially, islet capillaries form part of the general capillary bed of the gland, but subsequently they develop a direct arteriolar supply and venous drainage. The capillary connections with the exocrine bed are retained to form the basis of an insulo-acinar portal system. The volume fraction of islet vascularity remains constant at 19% from birth to adulthood, while the volume fraction of the intra-insular capillaries increases gradually in the first week; it accounts for half the total islet vascularity by day 14 and two thirds of total islet vascularity in the adult.