Carnitine in the streptozotocin-diabetic rat.

Rats made moderately diabetic by streptozotocin (decreased growth without decreased body mass, blood glucose, 588-840 mg/dl) and nondiabetic rats were either fed a purified diet with no measurable carnitine (diet 1), the same diet supplemented with carnitine (44.5 nmol/g food, diet 2), or a closed formula, nonpurified diet (3.3 nmol/g food, diet 3). Levels of total carnitine (free + acyl) were lower (P less than 0.05) in plasma, heart, soleus, extensor digitorum longus and kidney of rats fed diet 1 compared to those fed diet 2. Liver carnitine in diabetic animals was 2.6- to 4.4-fold higher than in nondiabetic animals with urinary carnitine of rats fed diet 1 being four times greater in diabetic than in nondiabetic rats. Other changes in tissue total carnitine were less pronounced. Compared to diabetic rats, insulin-treated diabetics had lower urinary excretion of carnitine and blood glucose levels (P less than 0.05), and tissue carnitine approximating nondiabetic levels. Significant catabolism of carnitine was not found. Apparent carnitine biosynthesis (diet 1) showed no difference between nondiabetic and diabetics (31.5 +/- 1.6 and 31.2 +/- 2.2 nmol/g of body weight per day, respectively) suggesting elevated liver levels resulted from redistribution.