Insulin Recovery in Pancreas and Host Organs of Islet Grafts^*

Abstract

The method of insulin determination is a useful tool for detecting surviving beta cells in the pancreas of diabetic animals and in organs used as sites of islet graft. Therefore, we have studied the insulin recovery in tissue homogenates. The data show that a high recovery rate of insulin (more than 95%) was reached, when the phosphoric acid-alcoholic tissue extract was stored at -20 degrees C and diluted with RIA buffer immediately before radioimmunoassay. When acid-ethanol supernatants were neutralized the recovery rate was diminished to 73.4 +/- 4.0% in pancreas and to 61.0 +/- 6.2% in liver homogenates, respectively. Glucagon was degraded when diluted extracts were stored at -20 degrees C for different periods of time. The diabetogenic action of streptozotocin (STZ) could be demonstrated for doses ranging between 30 and 55 mg/kg body weight. STZ caused a dose-dependent decrease of pancreatic insulin whereas the glucagon content was significantly enhanced in diabetic animals. The glucagon content was not normalized when normoglycemia was achieved by syngeneic islet transplantation. Insulin extracted from spleen used as a site for transplantation of 900 neonatal rat islets showed a high biological variation ranging from 0.7 to 6.4 nmol insulin per spleen, 10-100% of the content of the equivalent number of freshly isolated islets these animals received.

Spontaneous Recovery of Streptozotocin Diabetes in Mice

“…The whole pancreas or only the ventral part of the tissue was prepared, immediately frozen, weighed and stored at 20°C until extraction for estimation of the pancreatic insulin content. The extraction was carried out with acidic ethanol (Ziegler et al, 1985a) using glass potter homogenisators with two different luminaries. Insulin content of the extract was analysed by RIA (Beech et al, 1984).…”

Efficacy of the dipeptidyl peptidase IV inhibitor isoleucine thiazolidide (P32/98) in fatty Zucker rats with incipient and manifest impaired glucose tolerance

“…A pancreatic biopsy of approximately 30 mg wet weight was obtained. The tissue was quickly frozen in liquid nitrogen and stored until acid extraction and radioimmunological estimation of insulin content [20].…”

Prospective Investigations of Long-term Normoglycaemic BB/OK-rats: Serial Determination of Glucose Tolerance, Insulitis, B-cell Volume Density and Pancreatic Insulin Content

“…The blood glucose was measured using a Beckman glucose analyzer (Beckman Instruments, Fullerton CA, USA). The pancreatic part to be extracted was weighed, quickly frozen in liquid nitrogen and stored at 25 °C until acid extraction, which was performed as described in detail earlier (Ziegler et al, 1985). The extracted insulin was radioimmunologically measured (Gottschling et al, 1978).…”