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 s treptozotocin (STZ)-diabetic rats, based on the exponentially tapered T-tub e model. Rats given STZ 65 mg kg(-1) i.v. are compared with untreated weigh t- and age-matched controls. A high-fidelity pressure sensor and electromag netic flow probe measured pulsatile pressure and flow waves in the ascendin g aorta, respectively. Diabetic rats exhibit isobaric vasodilatation that i s 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 to tal peripheral compliance (2.86 +/- 0.70 mu l mmHg(-1)) than do weight- (1. 77 +/- 0.34 mu l mmHg(-1)) and age-matched (1.87 +/- 0.69 mu l mmHg(-1)) co ntrols. Aortic characteristic impedance is reduced from 0.017 +/- 0.003 mmH g min kg ml(-1) in weight- and 0.020 +/- 0.004 mmHg min kg ml(-1) in age-ma tched controls to 0.010 +/- 0.004 mmHg min kg ml(-1) in diabetic rats. More over, diabetic rats show shorter wave transit time in lower body circulatio n (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 resi stance 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 ao rtic distensibility of STZ-diabetic rats is manifest on the reduced wave tr ansit time rather than on the diminished aortic characteristic impedance. ( C) 2000 Academic Press.