Pancreatic islet blood flow and its measurement

Abstract

Pancreatic islets are richly vascularized, and islet blood vessels are uniquely adapted to maintain and support the internal milieu of the islets favoring normal endocrine function. Islet blood flow is normally very high compared with that to the exocrine pancreas and is autonomously regulated through complex interactions between the nervous system, metabolites from insulin secreting β-cells, endothelium-derived mediators, and hormones. The islet blood flow is normally coupled to the needs for insulin release and is usually disturbed during glucose intolerance and overt diabetes. The present review provides a brief background on islet vascular function and especially focuses on available techniques to measure islet blood perfusion. The gold standard for islet blood flow measurements in experimental animals is the microsphere technique, and its advantages and disadvantages will be discussed. In humans there are still no methods to measure islet blood flow selectively, but new developments in radiological techniques hold great hopes for the future.

Keywords: Blood flow measurements; islet blood flow; microspheres; pancreatic islets.

Figure 1.

Blood flow values in exocrine and endocrine pancreatic parenchyma. Modified from Jansson and Carlsson (15).

Figure 2.

Estimation of intra-islet insulin concentrations based on previously published data on insulin release (168) and islet blood flow (87).

Figure 3.

Correlation between islet blood flow (IBF) and total pancreatic blood flow (PBF) on anesthetized normoglycemic Sprague-Dawley rats. Data are based on 36 recent control experiments. (Pancreatic blood flow =0.0466 + (0.0158 × islet blood flow)). P < 0.001.

Figure 4.

A: Pancreatic islet being perfused after cannulation with a glass pipette. The islet has a diameter of 250 μm. B: A close-up of the arteriole showing two rows of vascular smooth muscle. The diameter of the arteriole is 34 μm.