Contractile responses to ouabain and K+-free solution in aorta from hypertensive rats.
This study characterizes isometric force development in response to ouabain and K+-free solution in isolated aortic strips from spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. SHR aortas were more sensitive to ouabain than those from WKY (threshold: SHR, 3.1 X 10(-5) M; WKY, 25.6 X 10(-5) M), and force development in response to 10(-3) M ouabain was greater in SHR (SHR, 586 +/- 51 mg; WKY, 245 +/- 24 mg). Monensin, a Na+ ionophore, potentiated contractile responses to ouabain, whereas amiloride, a Na+ channel blocker, and low Na+ solutions depressed contractile responses to ouabain. Contractile responses of SHR aortic strips to K+-free solution were faster than those of WKY aortic strips [time to half-maximal response (t1/2): SHR, 24 +/- 5 min; WKY, 47 +/- 4 min]. Maximal force development by aortic strips from SHR in response to K+-free solution was not different from that of WKY aortic strips (SHR, 808 +/- 34 mg; WKY, 750 +/- 37 mg). Monensin (10(-5) M) increased the rate of force development to K+-free solution to a greater extent in WKY aortic strips than in those from SHR (t1/2: SHR, 3 +/- 1 min; WKY, 4 +/- 2 min). Amiloride and low Na+ solution depressed contractile responses to K+-free solution in both SHR and WKY aortic strips. These observations demonstrate that SHR aortas are more responsive to ouabain and K+-free solution compared with WKY aortas. Contractile responses to ouabain and K+-free solution were sensitive to experimental interventions that alter transmembrane Na+ movements.(ABSTRACT TRUNCATED AT 250 WORDS)
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D008985:Monensin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology*; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011919:Rats, Inbred Strains / Q000502:physiology*; D012964:Sodium / Q000502:physiology
D010042:Ouabain; D000584:Amiloride; D008985:Monensin; D012964:Sodium; D011188:Potassium