Neonatal rats were treated with MSG (4G/Kg daily for 7 days). Glucose tolerance tests (GTT) were performed at 32, 65 and 70 weeks. After one year there was evidence of Type II diabetes, and the blood glucose levels were significantly greater than the controls for several points in the GTT; islet beta-cells were unchanged, cataracts were often present and there was central obesity.
The amines in the heart, proximal tail artery, kidneys and adrenals were extracted after decapitation and analysed using HPLC. At 32 weeks of age there were no significant differences between MSG-treated and control rats in the GTT and in amine concentrations, except that the renal level of adrenaline (ADR) and serotonin (SER) increased by around 50% in the experimental group.
At 65 weeks of age, 3 out or 5 points in the GTT were significantly different from controls. There were significant reductions in cardiac noradrenaline (NA), ADR, 5-hydroxyindoleacetic acid (HIAA) and dopamine (DOP), and in arterial NA, ADR, DOP and SER. Adrenal NA, ADR and SER increased significantly. Renal SER remained significantly increased, but adrenaline fell.
At 70 weeks of age, 5 out of 5 points in the GTT were significantly greater than controls. Cardiac NA fell, but not significantly, and DOP and HIAA were significantly less than controls; arterial NA, SER and DOP also fell significantly. Adrenal NA and ADR were significantly increased compared with the controls. Renal SER remained high, and DOP fell significantly.
There is evidence of a decline of [NA] in the heart and artery, no change in the kidney and an increase in the adrenal after Type II diabetes become established. At the same time, [DOP] in heart and artery also fell. These findings may be of relevance to autonomic neuropathy and cardiovascular control in Type II diabetes.