title: Cerebral artery responses to pressure and flow in uremic hypertensive and spontaneously hypertensive rats.
abstract: Impaired cerebral blood flow autoregulation is seen in uremic hypertension, whereas in nonuremic hypertension autoregulation is shifted toward higher perfusion pressure. The cerebral artery constricts in response to a rise in either lumen pressure or flow; we examined these responses in isolated middle cerebral artery segments from uremic Wistar-Kyoto rats (WKYU), normotensive control rats (WKYC), and spontaneously hypertensive rats (SHR). Pressure-induced (myogenic) constriction developed at 100 mmHg; lumen flow was then increased in steps from 0 to 98 microl/min. Some vessels were studied after endothelium ablation. Myogenic constriction was significantly lower in WKYU (28 +/- 2.9%) compared with both WKYC (39 +/- 2.5%, P = 0.035) and SHR (40 +/- 3.1%, P = 0.018). Flow caused constriction of arteries from all groups in an endothelium-independent manner. The response to flow was similar in WKYU and WKYC, whereas SHR displayed increased constriction compared with WKYU (P < 0.001) and WKYC (P < 0.001). We conclude that cerebral myogenic constriction is decreased in WKYU, whereas flow-induced constriction is enhanced in SHR.
authors.affiliation: Anthony Raine Research Laboratories, St. Bartholomew's Hospital, London EC1A 7BE, United Kingdom. dinew@tiscali.co.uk
authors.forename: D I
authors.initials: DI
authors.lastname: New
authors.forename: A M S
authors.initials: AM
authors.lastname: Chesser
authors.forename: R C
authors.initials: RC
authors.lastname: Thuraisingham
authors.forename: M M
authors.initials: MM
authors.lastname: Yaqoob
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D004730:Endothelium, Vascular / Q000502:physiology; D006973:Hypertension / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D020768:Middle Cerebral Artery / Q000503:physiopathology*; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014511:Uremia / Q000150:complications*; D014661:Vasoconstriction