Studies in Spiny Mice (Acomys Cahirinus): Metabolic State and Pancreatic Insulin Release in Vitro

Abstract

Incidence of diabetes, serum immunoreactive insulin (IRI) levels, and pancreatic IRI content have been studied in a colony of some 700 spiny mice (Acomys cahirinus) held under laboratory conditions with unlimited access to food. The overall incidence of diabetes was about 15 %. Three types of diabetic syndrome could be defined: 1. Intermittent diabetes, where gross glycosuria or hyperglycemia persisted for several months but disappeared spontaneously. 2. Non-ketotic diabetes, usually occurring between 9 and 14 months of age and evolving to ketotic diabetes within 1 to 6 months after discovery. 3. Ketotic diabetes. Only "intermittent" diabetes appeared to be associated with obesity. Gross congenital hyperplasia of the islets of Langerhans occurred in all animals, irrespective of the incidence of diabetes. In non-diabetic spiny mice, both mean serum IRI and pancreatic IRI content were higher than in other strains of mice, variation between individuals being considerable. Serum IRI concentrations were highest in intermittent diabetic animals and lowest in ketotic diabetics. Pancreatic IRI content of intermittent diabetic animals was higher than that observed in any other obese hyperglycemic syndrome studied thus far. In relation to pancreatic IRI content, serum IRI of spiny mice - irrespective of the metabolic state - was lower than that of Swiss mice, NZO or obob mice. Preliminary studies of insulin secretion from pieces of pancreas perifused in vitro suggest that decreased responsiveness of Acomys pancreas to known stimulators of insulin release may be characteristic of our strain of this species. 1 Supported in part by the Fonds National Suisse de la Recherche Scientifique (Grant Nr. 4848.3) Berne, Switzerland,and by a grant-in-aid from Sandoz Pharmaceuticals, Basel, Switzerland.