Active and passive mechanical properties of isolated arterioles from STZ-induced diabetic rats. Effect of aminoguanidine treatment.

Studies were performed to examine the effect of experimental diabetes (4-6 weeks duration) on both the passive elastic and active myogenic properties of isolated skeletal muscle arterioles. Studies were conducted on untreated streptozotocin (60 mg/kg)-induced diabetic rats and in similar rats treated daily with either amino-guanidine (25 mg/kg) or methylguanidine (25 mg/kg). First-order cremaster muscle arterioles were isolated, cannulated, and pressurized in the absence of intraluminal flow. Video microscopy was used to determine relationships between arteriolar diameter and intraluminal pressure both in the active and passive (o mmol/l Ca(2+)-2 mmol/l EGTA superfusated) tes. The measurements were used to calculate active myogenic responses, arteriolar distensibility, and stress-strain relationships. Under passive conditions, arterioles from untreated diabetic animals appeared to be stiffer and less distensible compared with similar arterioles from control animals. Under active conditions, i.e., in the presence of extracellular Ca2+, arterioles from the untreated diabetic group showed impaired myogenic reactivity as evidenced by a significant (P < 0.001) reduction in the negative slope of the pressure-diameter relationship over a physiological range of intraluminal pressures. Chronic treatment with aminoguanidine prevented the diabetes-induced changes in the active and passive properties of the isolated arterioles while treatment with methylguanidine appeared ineffective. Vasodilator responses to topically applied acetylcholine (10(-8) to 5 x 10(-6) mol/l) were significantly impaired in diabetic animals irrespective of treatment with aminoguanidine. The data indicate that experimental diabetes is associated with a decreased passive distensibility, or stiffening, of skeletal muscle arterioles that, in addition, may contribute to impaired active myogenic responses.