Thoracic Aorta Of Male Rats Research Articles

Acute administration of oestradiol or progesterone in a spinal cord ischaemia–reperfusion model in rats

Despite research into protective pharmacological adjuncts, paraplegia persists as a dreaded complication after thoracic and thoracoabdominal aortic interventions. Reports on gender-related neurological outcomes after ischaemic and traumatic brain injuries have led to increased interest in hormonal neuroprotective effects and have generated other studies seeking to prove the neuroprotective effects of the therapeutic administration of 17β-oestradiol and of progesterone. We hypothesised that acute administration of oestradiol or progesterone would prevent or attenuate spinal cord ischaemic injury induced by occlusion of the descending thoracic aorta. Male rats were divided into groups receiving 280 µg/kg of 17β-oestradiol or 4 mg/kg of progesterone or vehicle 30 min before transitory endovascular occlusion of the proximal descending thoracic aorta for 12 min. Hindlimb motor function was assessed by a functional grading scale (that of Basso, Beattie and Bresnahan) for 14 days after reperfusion. On the 14th day, a segment of the thoracolumbar spinal cord was harvested and prepared for histological and immunohistochemical analyses. There was significant impairment of the motor function of the hindlimb in the 3 study groups, with partial improvement noticed over time, but no difference was detected between the groups. On Day 1 of assessment, the 17β-oestradiol group had a functional score of 9.8 (0.0-16.5); the progesterone group, a score of 0.0 (0-17.1) and the control group, a score of 6.5 (0-16.9); on the 14th day, the 17β-oestradiol group had a functional score of 18.0 (4.4-19.4); the progesterone group had a score of 7.5 (0-18.5) and the control group had a score of 17.0 (0-19.9). Analysis of the grey matter showed that the number of viable neurons per section was not different between the study groups on the 14th day. Immunostaining of the spinal cord grey matter was also similar among the 3 groups. Acute administration of oestradiol or of progesterone 30 min before transitory occlusion of the proximal descending thoracic aorta of male rats could not prevent or attenuate spinal cord ischaemic injury based on an analysis of functional and histological outcomes.

Comparative effects of castration and antiandrogen treatment on the aortas of hypertensive and normotensive male rats.

Lowering androgen levels by gonadectomy or inhibiting circulating androgen by administration of the antiandrogen, BOMT, did not affect morphological or compositional changes induced by hypertension in the thoracic aorta of male rats. However, treatment with cyproterone acetate, another antiandrogenic drug, did result in the maintenance of total elastin and collagen at levels the same as those for the normotensive group and significantly lower than those for other treated and untreated hypertensive groups. In rapidly growing normotensive rats, neither castration nor administration of an antiandrogenic drug had any detectable effect on aortic wall morphology or composition regardless of whether the latter was expressed in absolute or relative terms. These findings suggest that growth and hypertension result in the accumulation of connective tissue proteins, elastin, and collagen in the blood vessel wall by different, independent mechanisms.

Long-term effects of hypertension on the rat aortic wall and their relation to concurrent aging changes. Morphological and chemical studies.

The effects of long-term (16 months) hypertension on the thoracic aorta of male rats were compared to previously reported short-term (2.5 months) changes and to concurrent aging changes. Hypertension was produced by clipping a renal artery. Although short-term hypertension was characterized by a disproportionate increase in noncollagenous alkali-soluble proteins, which have been attributed primarily to vascular smooth muscle, with long-term hypertension there was no further increase in these proteins but instead there were striking increases in mural accumulations of elastin and collagen. Chronically elevated wall tension in hypertensive vessels was associated with a progressive increase in wall thickness which resulted in a value for wall stress no different from that of control vessels. Concurrent aging changes were qualitatively similar to, but much less pronounced than, those seen with hypertension and were attributed to an increase in wall tension in controls resulting from a combination of significant increases in diameter and systolic blood pressure with age. This study of the interaction of vessel structure and function has revealed common features of what appears to be a diverse group of vascular alterations.