Studies on a stable, mild diabetes induced by streptozotocin in rats

A stable, mild diabetes in rats maintained on a normal laboratory diet was induced by a single i.p. injection of streptozotocin. Irreversible damage of the pancreatic islet B cells was complete by 3 days after treatment and plasma immunoreactive insulin was undetectable throughout the remaining 12-week period of investigation. The diabetes was characterized by hyperglycaemia of over 30 mM and a constant elevation of plasma alanine and branch-chain amino acids throughout the 12 weeks. In contrast to severe diabetes, plasma free fatty acids rose only gradually from normal values to reach 1.5 mM by week 12, ketone bodies were only slightly elevated (0.7 mM maximum) and liver glycogen was maintained throughout at around 30% of the normal, fed value. Starvation for up to 40 h caused only slight changes (in contrast with non-diabetic animals) and in particular no changes in free fatty acid or ketone bodies were found. These metabolic results are discussed in relation to the mechanisms thought to control those processes.