Abstract
Summary
Insulin content and peptidase activity were determined in microdissected rat islet tissue at various intervals following a single diabetogenic dose of streptozotocin. The islet insulin content was decreased to approximately 53% of the normal control value at 12 hr and to 4% at 24 hr after the administration of the drug. The plasma insulin levels in general paralleled the islet insulin content.
Islet peptidase activity showed significant changes following streptozotocin administration. After 12 hr the enzyme activity was considerably decreased, but after 24 hr there was a sharp increase in the peptidase activity. When the values for insulin content and peptidase activity of islet tissue obtained from rats made diabetic with alloxan and streptozotocin were compared, it was evident that the proteolytic enzyme was elevated at about the same time that islet insulin had completely disappeared.
When either drug was injected in the rats and an hour later a load of glucose was administered intraperitoneally, the plasma insulin levels were not altered. By contrast, the saline-injected animals responded to glucose administration with a significant elevation of plasma insulin. This indicated that the two diabetogenic agents affected the sensitivity of the B-cells to hyperglycemia. Since alloxan is reported to alter the permeability of B-cell membrane, it is concluded that streptozotocin may also affect the B-cell permeability.
It is indeed a pleasure to acknowledge the excellent technical assistance given by Mrs. Gayle Walz.
Get full access to this article
View all access options for this article.