DIFFERENTIAL ALTERATIONS OF COMMON CAROTID AND FEMORAL-ARTERY DISTENSIBILITY IN 12-WEEK-OLD SPONTANEOUSLY HYPERTENSIVE RATS

Objective In essential hypertension, the mechanical properties of the radial artery have been shown to be largely unaltered, whereas more co ntroversial and less reliable data have been obtained for the common c arotid artery. We therefore examined the distensibility/pressure relat ionships of the predominantly elastic common carotid artery and of the predominantly muscle-type femoral artery in 12-week-old normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Met hods Eleven 12-week-old SHR and 10 age-matched WKY rats were anestheti zed with sodium pentobarbitone. Blood pressure and pulse rate were mea sured by catheters inserted in the common carotid and in the femoral a rteries, while contralateral arterial diameter was continuously record ed via an echo-tracking device. Arterial compliance was derived accord ing to the Langewouters formula, and its values were normalized for th e diameter, to obtain distensibility/pressure curves and to calculate the distensibility index. The Peterson elastic modulus was also calcul ated in order to obtain a pressure-independent estimate of arterial me chanical properties. Results Femoral artery distensibility/pressure cu rves and distensibility index were similar in the two groups of rats, the latter being 1.13 +/- 0.13 mm/mmHg10(-3) in SHR and 1.28 +/- 0.15 mm/mmHg10(-3) in WKY rats (means +/- SEM; NS). In contrast, in SHR, co mmon carotid artery mechanical properties were clearly impaired, as sh own by a marked reduction in distensibility index (2.55 +/- 0.16 mm/mm Hg10(-3) in SHR versus 3.4 +/- 0.3 mm/mmHg10(-3) in WKY rats; P < 0.05 ), and by a significant increase in the Peterson elastic modulus. Conc lusions In the SHR model, high blood pressure alters the mechanics of large arteries even in the relatively early stage of the disease; howe ver, the alterations are not homogeneous inasmuch elastic-type vessels are affected to a much greater extent than muscle-type vessels. (C) R apid Science Publishers ISSN 0263-6352.