Strict insulin therapy normalises organ nitrogen contents and the capacity of urea nitrogen synthesis in experimental diabetes in rats

Summary

Rats with experimental diabetes due to streptozotocin (75 mg/kg body weight) and free access to food were divided into two groups. One group (n=9) was optimally treated with insulin (glucosuria <4.0 mmol/24 h), using heat treated very long-acting ultralente insulin. The other group (n=10) was poorly treated with insulin (glucosuria 20–30 mmol/24 h).

The nitrogen balance and energy balance of optimally treated diabetic rats was positive and not different from the control group (n=6). In the poorly treated diabetic rats the nitrogen balance was reduced whereas the energy balance was not different from that of control rats. After 4 weeks the fasting glucagon was: 50±21 ng/l (mean±SEM) in control rats, 62±18 ng/l in optimally treated diabetic rats and 249±58 ng/l in poorly treated diabetic rats (p<0.01). The capacity of urea nitrogen synthesis determined during alanine loading was: 9.6±1.0 umol/(min 100 g body weight) in control rats, 10.6±1.7 umol/(min 100 g body weight) in optimally treated diabetic rats and 17.3±1.3 umol/(min 100 g body weight) in poorly treated diabetic rats (p<0.01).

Nitrogen contents of carcass, heart, intestines, liver, and kidneys as determined by Kjeldahl analyses were identical in control rats and optimally treated diabetic rats. In the poorly treated diabetic rats carcass-nitrogen and heart-nitrogen contents were reduced to 89% of the control value (p<0.01), whereas the kidney-nitrogen content was increased to 112% of the control value (p<0.01).

Strict insulin therapy in experimental diabetes leads to a normalisation of nitrogen metabolism and hyperglucagonaemia, whereas less than optimally insulin treated rats show marked abnormalities in nitrogen metabolism as well as hyperglucagonaemia.