Biomedical subjects

Orjan Källskog

Publications and source records attributed to Orjan Källskog.

6 recordsLinked to original sources

PubMed2005

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

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.

Animals↗

PubMed2005

Marked increase in white adipose tissue blood perfusion in the type 2 diabetic GK rat.

The aim of the present study was to evaluate and cor-relate islet to brown and white adipose tissue (WAT) blood perfusion in one obese rat and one nonobese rat with type 2 diabetes (obese Zucker [OZ] and GK rats, respectively). We measured blood perfusion with a microsphere technique in anesthetized animals and subsequently estimated the blood flow to seven different WAT depots and brown adipose tissue, in addition to the whole pancreas and pancreatic islets. Both GK and OZ rats had higher islet blood perfusion than their respective control strains. Adipose tissue blood flow (ATBF) was similar to or lower than that of controls in the normoglycemic OZ rats. GK rats, however, had 5-10 times higher blood perfusion than control Wistar rats in most WAT depots. Vascular density and macrophage numbers in WAT did not differ between the different strains. The discrepancy in ATBF between the obese-normoglycemic and type 2 diabetic rats opens the intriguing possibility that changes in this blood perfusion may influence and/or modulate the beta-cell dysfunction in type 2 diabetes.

Adipose Tissue↗

PubMed2005

Acute effects of a 50% partial pancreatectomy on total pancreatic and islet blood flow in rats.

OBJECTIVES: The aim of the study was to investigate how an acute increase in functional demand for insulin release affected islet blood perfusion in anesthetized rats. METHODS: We measured total pancreatic and islet blood flow with differently colored microspheres before and 30 minutes after a 50% partial pancreatectomy. RESULTS: The blood glucose concentrations increased in the animals subjected to partial pancreatectomy. The fact that serum insulin concentrations remained unaffected implies that the islets in fact doubled their output of insulin to maintain the same degree of insulinemia. Still, pancreatic islet blood flow was the same as in the sham-operated animals. Likewise, the number of perfused pancreatic islets and the flow distribution between individual islets were not influenced by the partial pancreatectomy. CONCLUSIONS: We conclude that the acute demand for insulin secretion induced by a 50% partial pancreatectomy is not necessarily associated with an acute increase in islet blood perfusion. These findings suggest that basal islet blood flow is high enough to allow for short-term changes in hormone release without simultaneous changes in blood perfusion.

Anesthesia↗

PubMed2004

Promoting islet cell function after transplantation.

Engraftment (i.e., the adaptation of transplanted pancreatic islets to their new surroundings with regard to revascularization, reinnervation, and reorganization of other stromal compartments) is of crucial importance for the survival and function of the endocrine cells. Previous studies suggest that transplantation induces both vascular and stromal dysfunctions in the implanted islets when compared with endogenous islets. Thus the vascular density and the blood perfusion of islet grafts is decreased and accompanied with a capillary hypertension. This leads to hypoxic conditions, with an associated shift toward anaerobic metabolism in grafted islets. An improved engraftment will prevent or compensate for the vascular/stromal dysfunction seen in transplanted islets and thereby augment survival of the islet implant. By such means the number of islets needed to cure the recipient will be lessened. This will increase the number of patients that can be transplanted with the limited material available.

Animals↗

PubMed2002

Glucose-induced islet blood flow increase in rats: interaction between nervous and metabolic mediators.

This study investigated the mechanisms for glucose-induced islet blood flow increase in rats. The effects of adenosine, adenosine receptor antagonists, and vagotomy on islet blood flow were evaluated with a microsphere technique. Vagotomy prevented the islet blood flow increase expected 3, 10, and 20 min after injection of glucose, whereas theophylline (a nonspecific adenosine receptor antagonist) prevented the islet blood flow increase from occurring 10 and 20 min after glucose administration. Administration of selective adenosine receptor antagonists suggested that the response to theophylline was mediated by A1 receptors. Exogenous administration of adenosine did not affect islet blood flow, but local accumulation of adenosine, induced by the adenosine uptake inhibitor dipyridamole, caused a doubling of islet blood flow. In conclusion, the increased islet blood flow seen 3 min after induction of hyperglycemia is caused by the vagal nerve, whereas the increase in islet blood perfusion seen at 10 and 20 min after glucose administration is caused by both the vagal nerve and adenosine.

Adenosine↗

PubMed2002

Multiple injections of coloured microspheres for islet blood flow measurements in anaesthetised rats: influence of microsphere size.

We investigated if coloured microspheres could be used for repeated measurements of pancreatic islet blood flow in rats. An initial injection of 1.0-1.5 x 10(5) microspheres (black colour), with a size of 10 or 15 microm, was made into the ascending aorta, while an arterial reference sample was collected from the femoral artery. Twelve min later, 1 ml of saline or 30% D-glucose was injected intravenously. Three min after this injection a second injection of 10- or 15-microm microspheres (green colour) was given. The animals were then killed, and the pancreas and adrenals were removed and samples (150-200 mg) were secured from the duodenum, ileum, colon, right kidney and liver. The microsphere contents were determined with the aid of a freeze-thawing technique and blood flow values were calculated. Our results suggest that 10-microm microspheres, but not 15-microm microspheres, provide reproducible islet and total pancreatic blood flow measurements when repeatedly injected. Values for the blood flow to the intestines, kidney and liver were less sensitive to the size of the microspheres. We conclude that repeated administration of 15-microm microspheres induces a high risk for erroneous islet and total pancreatic blood flow measurements, whereas two such measurements can be performed if 10-microm microspheres are used.

Animals↗