Whole Pancreatic Blood Flow and Islet Blood Flow in Hypovolemic Hypotension in Rats

Abstract

The blood volume of adult, male rats was reduced with 5 ml (approximately 30% of the total blood volume) by bleeding, which reduced the mean arterial blood pressure (MAP) to 50 mm Hg. This hemorrhagic hypotension caused an increase in both serum glucose and serum insulin concentrations when compared with either normotensive control animals or with rats infused with nitroprusside to obtain an MAP similar to that of the bled animals. The blood perfusion of the whole pancreas was reduced in both groups of hypotensive animals but more markedly in those with hemorrhagic hypotension. The islet blood flow was reduced only in the bled animals. The percentage fraction of blood diverted through the islet organ was markedly increased in bled rats compared to the control animals, whilst this increase was less pronounced in the nitro-prusside-infused rats. The vascular conductance in the nitro-prusside-treated rats was unchanged for the whole gland, but increased for the islets. Both these values in bled animals were decreased. It is concluded that the blood flow regulation differs between the endocrine and exocrine parts of the pancreas in hypovolemic hypotension.

Autoregulation of Islet Graft Blood Flow Follows the Implantation

“…Previous studies on endogenous islets have suggested that they possess a strong autoregulation [5,16], which is similar to what is seen also in other endocrine organs such as the pituitary gland [17]. This is functionally important, since the capillaries in these blood vessels should impose only minor restrictions to the passage of hormones by containing fenestrated endothelial cells which may otherwise become damaged by barotrauma or fail to provide an adequate transport of the islet hormones [18,19].…”

Neuronal nitric oxide synthase and splanchnic blood flow in anaesthetized rats

“…The approximately 35–40% reduction in mean arterial blood pressure has previously been shown to have very little effect on islet and pancreatic blood flow in experiments where systemic blood pressure was reduced (Kvietys et al. 1982, Jansson 1992). We therefore deem it unlikely that the observed unchanged flow values depend on changes in blood pressure.…”

KATP Channels and Pancreatic Islet Blood Flow in Anesthetized Rats

“…However, it can be estimated, assuming an islet volume of 1-2%, that it is increased to the same degree as that to the whole pancreas. Thus, it seems as if opening of the K ATP channels induces most pronounced blood flow effects on islets and whole pancreas, despite the low blood pressure, which, nevertheless, is within the limits of autoregulation for the rat pancreas (29) and islets (30). Diazoxide had its most pronounced effects on total pancreatic blood perfusion, as manifested by the decreased fractional islet blood flow (i.e., a lowering of the fraction of blood diverted through the islets).…”