title: Prolonged isobaric relaxation time in small mesenteric arteries of the spontaneously hypertensive rat.
abstract: Prolonged isometric relaxation in hypertensive aortic and caudal arterial smooth muscle has been demonstrated; however, isobaric relaxation in resistance arteries is more pertinent to studies in hypertension. A comparative study of mesenteric arterial isobaric relaxation times was made using spontaneously hypertensive rats (SHR), normotensive Wistar-Kyoto rats (WKY), and MK-421 treated SHR (treatment commenced at 8 weeks of age and was maintained until sacrifice). Relaxation rates of vessels constricting against a range of pressures and achieving different degrees of narrowing or changes in circumference were analyzed. Comparisons were made between SHR, WKY, and MK-421 treated SHR arteries that had constricted from the same initial circumference and against the same magnitude of pressure. The SHR mesenteric arteries relaxed at a slower rate than did the WKY vessels. The normotensive MK-421 treated SHR showed the same prolonged relaxation rate as did the untreated SHR preparations. Thus the slower rate of relaxation in SHR arteries does not appear to be a consequence of the hypertension. Such prolonged time for narrowing would function to increase the average peripheral resistance and thus may contribute to the initiation and maintenance of increased blood pressure.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004558:Electric Stimulation; D004656:Enalapril / Q000494:pharmacology*; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D007700:Kinetics; D008638:Mesenteric Arteries / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
chemical_list: D004656:Enalapril