Relationship of Aortic Wall and Baroreceptor Properties during Development in Normotensive and Spontaneously Hypertensive Rats

We studied the relationship between aortic baroreceptor function and aortic wall properties in normotensive (NTR) and spontaneously hypertensive (SHR) rats 10-20 weeks old. Baroreceptor discharge, static pressure-volume (P-V), and pressure-radius relationships were measured in excised aortic segments. Histological studies of wall thickness and receptor numbers also were made. Circumferential wall stress and strain were calculated, as was the incremental elastic modulus (EINC). EINC in NTR's at 100 mm Hg was similar to values reported for in vivo human, dog, and rat aortas. At 10 weeks, SHR's had significantly elevated blood pressure, but SHR and NTR aortas had similar relationships among pressures, volumes, strains, and EINC's. Differences arose subsequently and, at 20 weeks, NTR aortas had larger volumes, larger strains, and smaller EINC's at equivalent pressures, whereas SHR aortas were unchanged. Thus the reduced distensibility of SHR relative to NTR aortas, rather than being due to retrogressive chang...