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 ± 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 (t( 1/2 )): 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 (t( 1/2 ); 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. The results are consistent with the hypothesis that vascular smooth muscle cells of SHR aortas have increased membrane permeability to Na+ and enhanced Na+ pump activity.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|State||Published - Jan 1 1986|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)