Pancreatic islet blood flow and its measurement

Endothelin-1 (ET-1) is a potent endothelium-derived vasoconstrictor, which also stimulates insulin release. The aim of the present study was to evaluate whether exogenously administered ET-1 affected pancreatic islet blood flow in vivo in rats and the islet arteriolar reactivity in vitro in mice. Furthermore, we aimed to determine the ET-receptor subtype that was involved in such responses. When applying a microsphere technique for measurements of islet blood perfusion in vivo, we found that ET-1 (5 nmol/kg) consistently and markedly decreased total pancreatic and especially islet blood flow, despite having only minor effects on blood pressure. Neither endothelin A (ETA) receptor (BQ-123) nor endothelin-B (ETB) receptor (BQ-788) antagonists, alone or in combination, could prevent this reduction in blood flow. To avoid confounding interactions in vivo, we also examined the arteriolar vascular reactivity in isolated, perfused mouse islets. In the latter preparation, we demonstrated a dose-dependent constriction in response to ET-1. Administration of BQ-123 prevented this, whereas BQ-788 induced a right shift in the response. In conclusion, the pancreatic islet vasculature is highly sensitive to exogenous ET-1, which mediates its effect mainly through ETA receptors.

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Duct ligation and pancreatic islet blood flow in rats: physiological growth of islets does not affect islet blood perfusion

Acta Endocrinologica ◽

10.1530/eje.1.01966 ◽

2005 ◽

Vol 153 (2) ◽

pp. 345-351 ◽

Cited By ~ 6

Author(s):

Leif Jansson ◽

Birgitta Bodin ◽

Örjan Källskog ◽

Arne Andersson

Keyword(s):

Blood Flow ◽

Pancreatic Islet ◽

Serum Insulin ◽

Blood Perfusion ◽

Islet Function ◽

Sprague Dawley ◽

Islet Mass ◽

Islet Blood Flow ◽

Sprague Dawley Rats ◽

Duct Ligation

Objectives: The aim of this study was to evaluate islet blood-flow changes during stimulated growth of the islet organ without any associated functional impairment of islet function. Design: A duct ligation encompassing the distal two-thirds of the pancreas was performed in adult, male Sprague–Dawley rats. Methods: Pancreatic islet blood flow was measured in duct-ligated and sham-operated rats 1, 2 or 4 weeks after surgery. In some animals studied 4 weeks after surgery, islet blood flow was also measured also during hyperglycaemic conditions. Results: A marked atrophy of the exocrine pancreas was seen in all duct-ligated rats. Blood glucose and serum insulin concentrations were normal. An increased islet mass was only seen 4 weeks after surgery. No differences in islet blood perfusion were noted at any time point after duct ligation. In both sham-operated and duct-ligated rats islet blood flow was increased during hyperglycaemia; the response was, however, slightly more pronounced in the duct-ligated part of the gland. Conclusions: Normal, physiological islet growth does not cause any major changes in the islet blood perfusion or its regulation. This is in contrast to findings during increased functional demands on the islets or during deteriorated islet function, when increased islet blood flow is consistently seen.

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Increased islet blood flow in obese rats: role of the autonomic nervous system

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.262.5.e736 ◽

1992 ◽

Vol 262 (5) ◽

pp. E736-E740 ◽

Cited By ~ 8

Author(s):

N. Atef ◽

A. Ktorza ◽

L. Picon ◽

L. Penicaud

Keyword(s):

Blood Flow ◽

Insulin Secretion ◽

Pancreatic Islet ◽

Ventromedial Hypothalamus ◽

Zucker Rats ◽

Islet Blood Flow ◽

Obese Rats ◽

Increased Sensitivity ◽

Obese Zucker Rats

Hyperinsulinemia, a main feature of both human and animal obesity, has been demonstrated to be due to both an increased sensitivity to nutrient secretagogues and an impairment of the nervous regulation of insulin secretion. Recent studies have shown that pancreatic islet blood flow increases under conditions associated with an enhanced insulin secretion. The aim of this study was to determine whether or not changes in islet blood flow are present in hyperinsulinemic obese rats. Using the nonradioactive microsphere technique, we were able to show a significantly higher islet blood flow in obese rats either of the Zucker strain or Wistar rats after lesion of the ventromedial hypothalamus than in their respective lean controls. Subdiaphragmatic vagotomy had no significant effect on basal islet blood flow of lean rats, whereas it decreased significantly that of obese Zucker rats. Conversely, clonidine, an alpha 2-adrenergic agonist, induced a higher decrease of islet blood flow in obese than in lean Zucker rats. The injection of an intravenous bolus of glucose (375 mg/kg iv) increased significantly more islet blood flow in obese than in lean Zucker rats. It is concluded that obese rats present an increased pancreatic islet blood flow, which may result, at least in part, from exaggerated parasympathetic activity and lower than normal sympathetic activity. This could participate in the hyperinsulinemia observed in these rats.

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