Arteriolar changes in developing and chronic stages of two-kidney, one clip hypertension.
Arteriolar internal and external diameters in the cremaster muscle of two-kidney, one clip hypertensive rats (2K1C) were measured in vivo with video microscopy, both before and after the topical application of adenosine (10(-4) M). Arteriolar density was determined by stereologic techniques. Mean arterial blood pressure was significantly elevated in the 2K1C rats, rising to 186 +/- 6 mm Hg by 8 weeks compared with 113 +/- 4 mm Hg in controls. Lumens of larger arterioles showed a structural reduction at 2 weeks of hypertension and remained at the same level through 8 weeks, while arterioles of control rats showed a progressive increase in diameter with age (101 +/- 6 microns in 2K1C vs. 158 +/- 8 microns in controls at 8 weeks after operation). Wall-to-lumen ratios of larger arterioles were significantly increased at 2, 4, and 8 weeks of hypertension, but cross-sectional wall area was significantly reduced at 8 weeks. Medial hypertrophy was not evident at any stage of hypertension. Arteriolar rarefaction of smaller arterioles was functional at 2 weeks and structural at 8 weeks of hypertension. Vascular tone of the smaller arterioles was elevated in the developing and chronic stages of hypertension. At 2 weeks of hypertension when the structural reduction in diameters of larger arterioles was progressing, the increased vasoconstriction and functional rarefaction may have contributed to the elevated resistance. At 8 weeks, the marked diameter reductions of larger arterioles (36% in first-order arterioles and 25% in second-order arterioles) account for most of the increased resistance to flow.
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Department of Physiology, Eastern Virginia Medical School, Norfolk 23501.
Prewitt
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Stacy
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D000005:Abdomen / Q000098:blood supply; D000818:Animals; D001158:Arteries / Q000503:physiopathology*; D001160:Arterioles / Q000503:physiopathology*; D002908:Chronic Disease; D006978:Hypertension, Renovascular / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D009129:Muscle Tonus; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors