Sex differences in myocardial contractility in the rat

Abstract

We examined the intrinsic contractile performance of papillary muscles removed from the left ventricle of male and female Wistar rats. Muscles were studied isometrically and isotonically, stimulated at 0.1 Hz, perfused with Tyrode's solution having an external calcium concentration = 2.4 and maintained at 30 ~ In addition, we examined muscle response to changes in external calcium, added norepinephrine or verapamil and alterations in contraction frequency. No significant change in peak isometric development tension was observed between male and female preparations. However, muscles from male rats showed a significantly greater isometric time-to-peak tension and time to 89 relaxation with a depression of both the maximum rate of tension rise and maximum rate of tension decay. Isotonically, although peak shortening showed no difference between male and female preparations, the maximum velocities of shortening and relaxation" were significantly depressed in muscles from male rats. Muscles from male animals also displayed significant prolongation of the time-to-peak shortening and time-to-peak velocity of shortening. These differences in papillary muscle performance were found over a wide range of muscle lengths, stimulus frequencies and bath concentrations of calcium, norepinephrine and verapamil. Thus differences in the intrinsic contractile performance between papillary muscle from male and female rats have been characterized.

Sex‐specific characteristics of cardiac function, geometry, and mass in young adult elite athletes

“…A number of studies have shown that healthy premeno- pausal women have higher ejection fractions when compared to healthy age-matched men (40,41) or to postmenopausal women (42). Similarly, papillary muscles from female rats have higher rates of shortening than male (43) and than gonadectomized female rats (44). The absence of sex-specific adaptive functional changes in our study suggests that this estrogen effect may be important for baseline cardiovascular characteristics, but not for adaptive functional cardiac changes due to exercise training.…”

Differential patterns of dynamic cardiovascular regulation as a function of task

“…Females have greater heart weight per body weight and greater aortic flow than males (Berg & Harmison, 1955;Shreiner, Weisfeldt & Shock, 1969). Moreover, in vitro studies of intrinsic myocardial contractile performance have revealed that females exhibit greater velocity of fiber shortening and shorter time to peak tension than males, even though no sex differences were observed in myocardial elasticity or in the peak tension developed (Capasso, Remily, Smith, & Sonnenblick, 1983). This evidence suggests that sex-related differences in myocardial contractile function may exist.…”

Steroid-induced cardiac contractility requires exogenous glucose,glycolysis and the sarcoplasmic reticulum in rainbow trout

“…Evidence suggests that there are sex differences in (1) intrinsic contractile properties (Capasso et al, 1983); (2) the positive inotropic response to Ca 2+ o (Wang et al, 1998); (3) Ca 2+ channels in the heart (Ishii et al, 1988) and (4) hormone responsiveness (Capasso et al, 1983;Schwertz et al, 1999). Whether there are sex differences in [Ca 2+ o ] or cardiac sensitivity to Ca 2+ in fishes is not known.…”

“…Thus, in contrast to sex steroids, it appears that the positive inotropy observed with Epi and Ca 2+ o in the ventricle of rainbow trout is mediated predominantly through trans-sarcolemmal Ca 2+ influx. (Capasso et al, 1983), including higher sensitivity to Ca 2+ in atria from female rat hearts compared with male hearts (Wang et al, 1998;Schwertz et al, 1999). In addition, Vizgirda et al hypothesized that SR Ca 2+ uptake via Ca…”