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Experimental diabetes: alterations in circulating dopamine-beta-hydroxylase and norepinephrine
Summary
Serum dopamine-beta-hydroxylase (DBH) levels significantly increase in diabetic rats, persisting for months. This elevation appears linked to diabetes itself, not norepinephrine levels, suggesting further investigation into sympathetic nervous system activity or DBH turnover.
Area of Science:
- Biochemistry
- Endocrinology
- Physiology
Background:
- Diabetes mellitus is a complex metabolic disorder with various physiological consequences.
- Dopamine-beta-hydroxylase (DBH) is a key enzyme in catecholamine synthesis, primarily norepinephrine.
- Alterations in DBH activity have been observed in various physiological and pathological conditions.
Purpose of the Study:
- To investigate the activity and levels of dopamine-beta-hydroxylase (DBH) in the serum of rats with experimentally induced diabetes.
- To explore the relationship between DBH activity, diabetes, and circulating catecholamine levels.
Main Methods:
- Experimental diabetes was induced in rats using Streptozotocin or Alloxan.
- DBH activity was measured in serum.
- Maximal velocity of the enzyme reaction and immunoprecipitation studies were performed.
- Hormone concentrations (thyroxin, triiodothyronine) were measured.
- Effects of adrenalectomy, insulin administration, and hormone replacement were assessed.
- Circulating norepinephrine levels were measured in arterial and venous blood.
Main Results:
- DBH activity in serum was increased at least 5-fold in diabetic rats, persisting for 7 months.
- Increased DBH activity correlated with increased maximal velocity and DBH protein levels.
- Thyroxin and triiodothyronine levels were reduced in diabetic rats, but hormone replacement did not normalize DBH activity.
- Adrenalectomy or insulin administration prevented both diabetes and elevated circulating DBH.
- Elevated norepinephrine levels were transient and only observed in venous blood early in diabetes.
- Circulating DBH levels did not correlate with norepinephrine levels.
Conclusions:
- Experimental diabetes in rats leads to a significant and persistent increase in circulating dopamine-beta-hydroxylase (DBH) activity and levels.
- The elevation in DBH is linked to the diabetic state, independent of norepinephrine levels, and is preventable by managing diabetes through insulin or adrenalectomy.
- Further research is needed to elucidate whether increased sympathetic nervous system activity or altered DBH turnover underlies these findings.