Increased resistance and impaired maximal vasodilation in normotensive vascular beds of rats with coarctation hypertension.

Abstract

SUMMARY To study the resistance of normotensive vascular beds in coarctation hypertension, we measured perfusion pressures of pump-perfused (blood), innervated, isolated hindlimbs of 12 rats (Group A) with 4 weeks of hypertension due to partial constriction of the abdominal aorta above the renal arteries, and of three control groups: 11 normotensive rats (Group B) with aorta sham-constricted, nine normotensive rats (Group C) with slight (5%) hindquarters atrophy due to partial constriction of the abdominal aorta below the renal arteries, and six rats with two-kidney, one clip Goldblatt hypertension (Group D). After aortic constriction, measured femoral arterial pressures in Group A rats remained normotensive. In hypertensive rats of Groups A and D, compared to normotensive Group B or C rats, hindlimb pressure-flow curves were displaced toward the pressure axis (p < 0.05). Compared to normotensive rats, drop in hindlimb resistance after acute local nerve section was increased in rats with coarctation hypertension. Residual resistance after maximal vasodilation with intraarterial sodium nitroprusside remained elevated in hypertensive rats of Groups A and D (p < 0.05), as compared to normotensive Group B or C rats; compared to Group B rats, this residual resistance in the coarcted rats of Group A was increased by 9%. Thus, in normotensive vascular beds of rats with chronic hypertension caused by aortic coarctation, resistance is elevated. The neurogenic component contributes to this high resistance, and structural vascular changes, indicated by impaired maximal vasodilation, may also contribute to the elevated resistance. It is most unlikely that these resistance changes are attributable to elevated hindlimb intravascular pressures. (Hypertension 1: 78-85, 1979 not be said to be merely secondary to increased intramodel for examining the effects of intravasvascular pressure. We have previously reported incular pressure on vascular structure and creased salt and water content in the walls of arteries function in hypertension, because the vascular beds from these normotensive vascular beds in rats with below the coarctation are not exposed to elevated coarctation hypertension. 1 It has been suggested that levels of pressure. Thus, abnormalities observed could such "waterlogging" of arterial walls increases vascular resistance and responses.

Overall hemodynamic pattern in coarctation of the abdominal aorta in conscious rats.

“…Although the differences in placement of the coarctation may cause different physiological effects, the overall clinical differences are small when the coarctation is either thoracic or abdominal and is located proximal to the renal arteries. Bell and Overbeck 21 did hindlimb perfusion studies in the rat and observed increased vascular resistance in these beds. However, the rats were anesthetized during the study, and no direct flow measurements were made.…”

Pressure-independent increases in vascular resistance in hypertension: role of sympathoadrenergic influences.

“…Then, after administration of supplemental anesthesia (chloralose 37.5 or 50 mg/kg and pentobarbital 2.2-3mg/kg i.v. ), we used previously described techniques 2 to measure perfusion pressure in the vascularly isolated, innervated, pumpperfused hindlimb vascular bed. Respiration was natural.…”

Nitroprusside-induced vascular relaxation in DOCA hypertensive rats.

“…To determine if the effects of nitroprusside are specific to the kidney, an entirely different vascular preparation (isolated strips from tail arteries) was also used. Antonaccio, et al 3 Triner, et al/ Hutchins, et al 6 Bell, et al 8 Godfraind and Dieu 7 Shibata and Cheng 1 Deragon, et al 8 Fink and Brody 9 Castro-Tavares 10 Folkow, et al 13 Specter, et al 11 Deragon, et al 8 Hutchins, et al 8 Hollenberg, et al 12 Cohen, et al 14 -" Control rats received implantations of Silastic strips without DOCA. The implantations were made in the left flank while the rats were under ether anesthesia.…”