Measurement of blood flow in pancreatic islets of the rat: effect of isoproterenol and norepinephrine

Abstract

Blood flow to the pancreatic islets of the anesthetized rat has been measured by application of microspheres, intravital staining of the endocrine tissue by Dithizon, and induction of organ transparency by incubation in glycerol. Thus the microspheres could be counted separately in the islet tissue and in the remaining organ. The total pancreatic blood flow in the rat amounted to 0.48 +/- 0.04 ml.min-1.g-1 and the flow fraction of the islet tissue to 1.22 +/- 0.09%, corresponding to a flow rate through the pancreatic islets of 5.42 +/- 0.63 microliters/min. When isoproterenol was applied (0.1 and 1.0 micrograms.kg-1.min-1 iv for 15 min), total pancreatic blood flow rose to 0.60 +/- 0.08 and 0.98 +/- 0.10 (P less than 0.01) ml.min-1.g-1, whereas the flow fraction to the islets decreased to 0.82 +/- 0.08 (P less than 0.01) and 0.61 +/- 0.07% (P less than 0.01). The absolute islet perfusion remained nearly unchanged. Norepinephrine (2.0 and 5.0 micrograms.kg-1.min-1 for 15 min) similarly increased total blood flow to 0.78 +/- 0.08 (P less than 0.01) and 0.64 +/- 0.08 ml.min-1.g-1) while reducing the islet flow fraction to 1.15 +/- 0.13 and 0.83 +/- 0.05% (P less than 0.01). The absolute flow rate through the islet tissue did not change significantly. The conclusion may be drawn from these experiments that changes in total pancreatic blood flow are not necessarily accompanied by corresponding changes in the perfusion rate of the endocrine islet tissue.

Hypoglycaemia induces decreased islet blood perfusion mediated by the central nervous system in normal and Type 2 diabetic GK rats

“…Compared to most studies on islet blood flow in adult rats [1,10,12,31,32] one group [14] obtained a considerably lower value (~2% vs 7-20%) for the control rats. Such low islet blood flow values have previously only been recorded in very young animals [16,33,34]. Another group [15] used an elegant technique with repeated injections of microspheres in conscious rats and showed no influence of insulin-induced hypoglycaemia on islet blood flow.…”

“…Influence on islet blood flow has been shown to be exerted by vagal [4], sympathetic [3,6,33,38], as well as peptidergic [39] nerves. Activation of all these nervous systems also seems to occur in the pancreas and its islets in response to hypoglycaemia [40].…”

The life story of the pancreatic B cell

“…The regulation of islet blood flow has become accessible to investigation relatively recently. The prerequisite of this has been the introduction of the microsphere method combined with various techniques for the differential counting of microspheres in the endocrine and exocrine pancreas [36][37][38]. The application of these techniques in the rat has confirmed the previous anatomical observation of a rich vascular supply to the islets in showing that not less than 10%-15% of the total pancreatic blood flow is diverted to the islets [39, 401.…”

The pancreatic islets in spontaneously hypertensive rats: islet blood flow and insulin production

“…Previous experiments have demonstrated that the islet vasculature responds to epinephrine with vasoconstriction (15), but there is some controversy with regard to the receptors involved (cf. 15,46). It should also be noted in this context that plasma catecholamines in SHR and WKY of different ages do not differ, but the increment seen after stress is greater in SHR (10).…”