Influence of ovariectomy on ventricular myocyte contraction in simulated diabetes

We studied the effect of ovariectomy (OVX) on cardiac contraction in myocyt es maintained under a 'diabetes-simulated high-glucose' environment. Female rats were ovariectomized or sham operated (SHAM) and kept for 6 weeks. Iso lated myocytes were maintained in a diabetes-simulated high [glucose] mediu m (HG; 25.5 mM) for 24 h before mechanical properties were measured. Contra ctile indices analyzed included peak shortening (PS), time to PS (TPS), tim e to 90% relengthening (TR90), maximal velocity of shortening and relengthe ning (+/- dL/dt), intracellular Ca2+ fura-2 fluorescence intensity and deca y rate (tau). Nitric oxide synthase (NOS) activity was also evaluated. OVX myocytes displayed a longer TR90, slower +/- dL/dt, lower fluorescence inte nsity and higher tau (slower decay rate) when compared to SHAM myocytes. in the SHAM group, HG exerted diabetes-like contractile dysfunctions, includi ng depressed PS, prolonged TR90, reduced fluorescence intensity, higher tau and enhanced NOS activity when compared to myocytes maintained in low [glu cose] medium (5.5 mM). Interestingly, the HG-induced mechanical alterations were significantly exaggerated (TPS, TR90 and tau), reversed (PS and NOS) or lost (+/- dL/dt and fluorescence intensity) in the OVX group. These data suggest that ovarian hormones play a role in the regulation of cardiac con tractile function, and may have potentially protective effects against diab etes-associated cardiac dysfunction. Copyright (C) 2001 National Science Co uncil, ROC and S. Karger AG, Basel.