A consistent model of insulin-dependent diabetes mellitus hypertension

Hypertension is frequently seen in insulin-dependent diabetes mellitus (IDDM), but the mechanism of the hypertension is unknown. An animal model of IDDM hypertension could be helpful in determining the mechanism, but experimental IDDM has been infrequently and irregularly associated with hypertension. In an attempt to develop a consistent model of IDDM hypertension, we superimposed streptozotocin (STZ)-induced IDDM on surgical reduction of renal mass (RRM) in Wistar rats. Seven groups of rats were studied: 1) 60% RRM receiving 65 mg/kg body weight (BW) STZ; 2) 60% RRM receiving 40 mg/kg BW STZ; 3) 25% RRM receiving 65 mg/kg BW STZ; 4) two kidney normal rats receiving 65 mg/kg BW STZ; 5) 60% RRM receiving vehicle (control for group 1); 6) 60% RRM receiving vehicle (control for group 2); and 7) 25% RRM receiving vehicle. STZ produced diabetes and hypertension within 1 to 2 weeks in all three groups of RRM rats but blood pressure was unaffected by 60% or 25% RRM alone. STZ alone had no effect on blood pressure until the 5th week when the blood pressure increased slightly. Progressive weight loss resulted from 65 mg/kg BW STZ combined with 60% RRM; the animals had to be terminated after 5 weeks. In only 60% of animals with 40 mg/kg BW STZ plus 60% RRM was IDDM produced. On the other hand, 65 mg/kg BW STZ in rats with 25% RRM regularly produced IDDM and hypertension without excessive loss of body weight. In these rats, albuminuria developed in 2 weeks. Extracellular fluid volume was elevated and plasma renin activity was depressed. The animals were healthy and hypertensive when killed at the 13th week. We suggest that the 25% RRM rat receiving 65 mg/kg BW STZ is a consistent model of IDDM hypertension, which may be useful in probing the mechanism of this type of hypertension.