| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 1980. Medicine Bibliography: leaves 95-112. The elevation of arterial blood pressure in the spontaneously hypertensive rat (SHR) has been postulated to be the result of increased vascular resistance and that such an augmentation of vascular resistance may be due, at least in part, to changes of the vessel wall. The present study is designed to examine this hypothesis. -- Animals from each strain of SHR, WAR and WKY were sacrificed at 2, 4, 5, 6, 7, 8, 12 and 18 weeks of age. Blood pressures from each group were obtained by intra-arterial cannulation. The volume fractions of SMC, collagen and elastin in the media of the abdominal aorta and of the left renal artery of 2, 4, 8, 12 and 18 weeks old animals were estimated by stereological analysis at the EM level. The estimated values of these components in the SHR were compared with those obtained from the WAR and the WKY controls. -- The systolic blood pressure in the SHR rose to a significant level from 5 weeks and further increased to a hypertensive level by 18 weeks of age, as compared with the controls. As revealed by stereological analysis of the medial composition of the abdominal aorta and the left renal artery of the SHR, no significant difference was observed when comparing these parameters with those of the controls. -- The results of the present study indicate that the medial components of the arteries studied were not significantly different among the three strains of rat, up to 18 weeks of age, while the systolic blood pressure of the SHR was elevated significantly from 5 weeks of age. -- The elevation of arterial blood pressure during the development of the SHR therefore appears not to be the result of morphological changes in the media of the abdominal aorta and the renal artery.
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