title: Differential freezing tolerance of rat pancreatic islets depending on their size variation.
abstract: We have investigated the freezing tolerance of rat pancreatic islets. Freshly isolated rat pancreatic islets were divided into three groups based on their longest diameter (small; 100 - 200 microns, medium; 201 - 300 microns, large; > 300 microns). They were then cryopreserved at a slow cooling rate (-0.3 degrees C/min) in the presence of dimethyl sulfoxide (Me2SO) or ethylene glycol (EG). After storage at -196 degrees C for 1 - 4 weeks, they were thawed and their ability to secrete insulin in response to fluctuations in glucose concentration was examined during three consecutive static incubations in vitro (1st; 2.8 mM, 2nd; 16.7 mM, 3rd; 2.8 mM). Morphological examination of the beta-granule population was determined by image analysis, and correlation with islets size was analyzed. The amount of insulin released from large-sized islets was significantly suppressed in EG (p < 0.05) and Me2SO (p < 0.01) groups compared to unfrozen islets. However, the mean volume of the large-sized islets isolated from one rat accounted for 43.0% of the total volume. On the other hand, the amount of insulin released from small- and medium-sized islets did not differ from those of unfrozen islets, and their mean volumes were 13.2 and 43.8% respectively. The percentage of cells with beta-granules was significantly correlated with size in both EG (r = -0.52) and Me2SO (r = -0.35) groups, but no significant correlation was observed in the unfrozen islets groups. These findings suggest that large-sized islets are more susceptible to freezing injury than small- or medium-sized islets. Moreover, the volume distribution of isolated islets indicated that it may be important to retain the ability of insulin secretion from the large-sized islets.
authors.affiliation: Department of Veterinary Surgery, Yamaguchi University, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Sakonju
authors.forename: Y
authors.initials: Y
authors.lastname: Taura
authors.forename: K
authors.initials: K
authors.lastname: Mamba
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Takimoto
authors.forename: M
authors.initials: M
authors.lastname: Nakaichi
authors.forename: S
authors.initials: S
authors.lastname: Nakama
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods / Q000592:standards*; D003451:Cryoprotective Agents / Q000592:standards; D004121:Dimethyl Sulfoxide / Q000592:standards; D004305:Dose-Response Relationship, Drug; D005026:Ethylene Glycols / Q000592:standards; D005260:Female; D005947:Glucose / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000033:anatomy & histology* / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D003451:Cryoprotective Agents; D005026:Ethylene Glycols; D007328:Insulin; D005947:Glucose; D004121:Dimethyl Sulfoxide