Spontaneously hypertensive rats exhibited longer mechanical refractory periods and more prominent aftercontractions than normotensive controls, likely representing genetic differences.
Differences in cardiac contractile properties between spontaneously hypertensive rats and normotensive controls likely represent genetic strain differences rather than direct consequences of hypertension.
Contractile properties of isolated papillary muscles from three age groups of spontaeously hypertensive rats (SHRs) were compared to those from age-matched Wistar-Kyoto rats (WKYs) to assess whether there were differences between the strains preceding and during the course of the hypertension. In all three age groups (7, 12, and 50 wk), the mechanical refractory periods (MRP) were longer and aftercontractions more prominent after paired pulse stimulation in preparations from SHRs than from age-matched WKYs. Other isometric twitch properties of SHR papillary muscles at Lmax were not different from WKYs, with the exception of a shorter half-relaxation time in the youngest SHR group. Although hypertension and cardiac hypertrophy increased in SHRs with age, aging had similar influences on most cardiac contractile properties in both strains. None of the isometric properties of papillary muscles from rats made hypertensive by Doca treatment were different from those in normotensive control preparations. This suggests that differences seen between SHRs and WKYs probably represent genetic differences between these strains and are not directly caused by the hypertension.
Lois Jane Heller (Sat,) conducted a other in Hypertension. Spontaneous hypertension (SHR strain) and Doca treatment vs. Age-matched Wistar-Kyoto rats (WKYs) and normotensive controls was evaluated on Contractile properties of isolated papillary muscles (mechanical refractory periods, aftercontractions, isometric twitch properties). Spontaneously hypertensive rats exhibited longer mechanical refractory periods and more prominent aftercontractions than normotensive controls, likely representing genetic differences.