Impaired Vascular Dynamics in Normotensive Diabetic Rats Induced by Streptozotocin: Tapered T-tube Model Analysis

This study is to explore the changes of arterial mechanical properties in streptozotocin (STZ)-diabetic rats, based on the exponentially tapered T-tube model. Rats given STZ 65 mg kg−1i.v. are compared with untreated weight- and age-matched controls. A high-fidelity pressure sensor and electromagnetic flow probe measured pulsatile pressure and flow waves in the ascending aorta, respectively. Diabetic rats exhibit isobaric vasodilatation that is characterized by an increase in cardiac output and no significant changes in aortic pressure. Total peripheral resistance of diabetic rats is lower than that of weight- and age-matched controls. Diabetic rats have higher total peripheral compliance (2.86±0.70 μl mm Hg−1) than do weight- (1.77±0.34 μl mm Hg−1) and age-matched (1.87±0.69 μl mm Hg−1) controls. Aortic characteristic impedance is reduced from 0.017±0.003 mm Hg min kg ml−1in weight- and 0.020±0.004 mm Hg min kg ml−1in age-matched controls to 0.010±0.004 mm Hg min kg ml−1in diabetic rats. Moreover, diabetic rats show shorter wave transit time in lower body circulation (17.86±1.91 ms) than do weight- (20.45±1.91) and age-matched (23.05±2.04 ms) controls. Under isobaric vasodilatation, the decreased resistance and increased compliance in peripheral circulation suggest that the contractile dysfunction of the smooth muscle cells may occur in resistance arterioles in diabetes. With unaltered aortic pressure, an impairment in aortic distensibility of STZ-diabetic rats is manifest on the reduced wave transit time rather than on the diminished aortic characteristic impedance.