Cardiovascular diseases are often considered to be a predominantly male health problem, and it has been suggested that testosterone exerts deleterious effects on cardiovascular function; however, few experimental studies support this suggestion. Moreover, the cellular and molecular mechanism(s) underlying vascular responses to testosterone is unknown. The present study has investigated the acute effects of testosterone on porcine coronary artery smooth muscle at the tissue and cellular levels. Contractile studies demonstrated that testosterone or dihydrotestosterone (a nonaromatizable metabolite) relaxed these arteries by an endothelium-independent mechanism involving potassium efflux. Direct evidence from patch-clamp studies confirmed that testosterone opened K(+) channels in single coronary myocytes, and further analysis identified this protein as the large-conductance, calcium- and voltage-activated potassium (BK(Ca)) channel. Moreover, inhibiting BK(Ca) channel activity significantly attenuated testosterone-induced coronary relaxation. These findings indicate that testosterone relaxes porcine coronary arteries predominantly by opening BK(Ca) channels in coronary myocytes, and this response may be associated with accumulation of cGMP. This novel mechanism may provide a better understanding of testosterone-induced vasorelaxation reported in recent experimental and early clinical studies.

Recent studies have established that testosterone (Tes) produces acute (nongenomic) vasorelaxation. This study examined the structural specificity of Tes-induced vasorelaxation and the role of vascular smooth muscle (VSM) K+ channels in rat thoracic aorta. Aortic rings from male Sprague-Dawley rats with (Endo+) and without endothelium (Endo-) were prepared for isometric tension recording. In Endo- aortas precontracted with phenylephrine, 5-300 microM Tes produced dose-dependent relaxation from 10 microM (4 +/- 1%) to 300 microM (100 +/- 1%). In paired Endo+ and Endo- aortas, Tes-induced vasorelaxation was slightly but significantly greater in Endo+ aortas (at 5-150 microM Tes); sensitivity (EC(50)) of the aorta to Tes was reduced by nearly one-half in Endo- vessels. Based on the sensitivity (EC(50)) of Endo- aortas, Tes, the active metabolite 5alpha-dihydrotestosterone, the major excretory metabolites androsterone and etiocholanolone, the nonpolar esters Tes-enanthate and Tes-hemisuccinate (THS), and THS conjugates to BSA (THS-BSA) exhibited relative potencies for vasorelaxation dramatically different from androgen receptor-mediated effects observed in reproductive tissues, with a rank order of THS-BSA > Tes > androsterone = THS = etiocholanolone > dihydrotestosterone >> Tes-enanthate. Pretreatment of aortas with 5 mM 4-aminopyridine attenuated Tes-induced vasorelaxation by an average of 44 +/- 2% (25-300 microM Tes). In contrast, pretreatment of aortas with other K+ channel inhibitors had no effect. These data reveal that Tes-induced vasorelaxation is a structurally specific effect of the androgen molecule, which is enhanced in more polar analogs that have a lower permeability to the VSM cell membrane, and that the effect of Tes involves activation of K+ efflux through K+ channels in VSM, perhaps via the voltage-dependent (delayed-rectifier) K+ channel.

Estrogens can either relax or contract arteries via rapid, nongenomic mechanisms involving classic estrogen receptors (ER). In addition to ERα and ERβ, estrogen may also stimulate G protein-coupled estrogen receptor 1 (GPER) in nonvascular tissue; however, a potential role for GPER in coronary arteries is unclear. The purpose of this study was to determine how GPER activity influenced coronary artery reactivity. In vitro isometric force recordings were performed on endothelium-denuded porcine arteries. These studies were augmented by RT-PCR and single-cell patch-clamp experiments. RT-PCR and immunoblot studies confirmed expression of GPER mRNA and protein, respectively, in smooth muscle from either porcine or human coronary arteries. G-1, a selective GPER agonist, produced a concentration-dependent relaxation of endothelium-denuded porcine coronary arteries in vitro. This response was attenuated by G15, a GPER-selective antagonist, or by inhibiting large-conductance calcium-activated potassium (BK(Ca)) channels with iberiotoxin, but not by inhibiting NO signaling. Last, single-channel patch-clamp studies demonstrated that G-1 stimulates BK(Ca) channel activity in intact smooth muscle cells from either porcine or human coronary arteries but had no effect on channels isolated in excised membrane patches. In summary, GPER activation relaxes coronary artery smooth muscle by increasing potassium efflux via BK(Ca) channels and requires an intact cellular signaling mechanism. This novel action of estrogen-like compounds may help clarify some of the controversy surrounding the vascular effects of estrogens.

. Gender differences in the expression of heat shock proteins: the effect of estrogen. Am J Physiol Heart Circ Physiol 285: H687-H692, 2003.. First published April 24, 2003 10.1152/ajpheart.01000. 2002The heat shock proteins (HSPs) are an important family of endogenous, protective proteins that are found in all tissues. In the heart, HSP72, the inducible form of HSP70, has been the most intensely studied. It is well established that HSP72 is induced with ischemia and is cardioprotective. Overexpression of other HSPs also is protective against cardiac injury. Recently, we observed that 17␤-estradiol increases levels of HSPs in male rat cardiac myocytes. We hypothesized that there were gender differences in HSP72 expression in the heart secondary to estrogen. To test this hypothesis, we examined cardiac levels of HSP72 by ELISA in male and female Sprague-Dawley rats. In addition, three other HSPs were assessed by Western blot (HSP27, HSP60, and HSP90). To determine whether estrogen status affected HSP72 expression in other muscles or tissues, two other muscle tissues, slow twitch muscle (soleus muscle) and fast twitch muscle (gastrocnemius muscle), were studied as well as two other organs, the kidney and liver. Because HSP72 is cardioprotective, and females are known to have less cardiovascular disease premenopause, the effects of ovariectomy were examined. We report that female Sprague-Dawley rat hearts have twice as much HSP72 as male hearts. Ovariectomy reduced the level of HSP72 in female hearts, and this could be prevented by estrogen replacement therapy. These data show that the expression of cardiac HSP72 is greater in female rats than in male rats, due to upregulation by estrogen.hormones; cardiovascular diseases; ischemia THE HEAT SHOCK PROTEINS (HSPs) are an important family of endogenous, protective proteins that are found in all tissues. In the heart, HSP72, the inducible form of HSP70, has been the most intensely studied. It is well established that HSP72 is upregulated with ischemia and is cardioprotective (11,12,18,21,22,26,29). Overexpression of other HSPs also is protective against cardiac injury (3,16,19). Recently, we observed that 17␤-estradiol increases levels of HSP72 in male rat cardiac myocytes but has no effect on HSP27, HSP60, or HSP90 (14). We hypothesized that there were gender differences in HSP72 expression related to estrogen. To test this hypothesis, we examined cardiac levels of HSP72 by ELISA. In addition, three other HSPs were compared by Western blot (HSP27, HSP60, and HSP90). To determine whether gender differences were found in other tissues, skeletal muscle [slow twitch muscle (STM; soleus muscle) and fast twitch muscle (FTM; gastrocnemius muscle)] as well as the kidney and liver were studied.Because HSP72 is cardioprotective, and females are known to have less cardiovascular disease premenopause, the effects of ovariectomy were compared with estrogen replacement on HSP72. We report that female Sprague-Dawley rat hearts have twice as much HSP72 as male hearts. Ovariectomy r...

October 7, 2009; doi:10.1152/ajpregu.00178.2009.-The risk for cardiovascular disease (CVD) increases with advancing age; however, the age at which CVD risk increases significantly is delayed by more than a decade in women compared with men. This cardioprotection, which women experience until menopause, is presumably due to the presence of ovarian hormones, in particular, estrogen. The purpose of this study was to determine how age and ovarian hormones affect flowinduced vasodilation in the coronary resistance vasculature. Coronary arterioles were isolated from young (6 mo), middle-aged (14 mo), and old (24 mo) intact, ovariectomized (OVX), and ovariectomized ϩ estrogen replaced (OVE) female Fischer-344 rats to assess flowinduced vasodilation. Advancing age impaired flow-induced dilation of coronary arterioles (young: 50 Ϯ 4 vs. old: 34 Ϯ 6; % relaxation). Ovariectomy reduced flow-induced dilation in arterioles from young females, and estrogen replacement restored vasodilation to flow. In aged females, flow-induced vasodilation of arterioles was unaltered by OVX; however, estrogen replacement improved flow-induced dilation by ϳ160%. The contribution of nitric oxide (NO) to flow-induced dilation, assessed by nitric oxide synthase (NOS) inhibition with N G -nitro-L-arginine methyl ester (L-NAME), declined with age. L-NAME did not alter flow-induced vasodilation in arterioles from OVX rats, regardless of age. In contrast, L-NAME reduced flowinduced vasodilation of arterioles from estrogen-replaced rats at all ages. These findings indicate that the age-induced decline of flowinduced, NO-mediated dilation in coronary arterioles of female rats is related, in part, to a loss of ovarian estrogen, and estrogen supplementation can improve flow-induced dilation, even at an advanced age.endothelial nitric oxide synthase; Akt; nitric oxide; ovariectomy THE RISK FOR CARDIOVASCULAR disease (CVD) and heart failure increase with advancing age; however, sexual dimorphism exists in the chronological development of these risks (22,47). Although the chronological rate of aging is independent of sex, mechanisms that regulate the cardiovascular system across the lifespan may differ dramatically between men and women. The risk for CVD in men begins to increase at approximately the same age that flow-mediated vasodilation begins to decline (5). Women also exhibit this age-related impairment of flow-mediated vasodilation; however, significant reduction of flow-mediated dilation becomes apparent at the age of menopause, more than a decade later than in men (5). The cardioprotection that women experience until menopause is presumably due to the presence of ovarian estrogen and results in a sex-related delay of the expression of CVD (49). Chronic estrogen treatment has been shown to enhance endothelial function in a number of vascular beds (27, 31, 39), in part, through a pathway involving activation of Akt/PKB and subsequent phosphorylation of endothelial nitric oxide synthase (eNOS) (3,10,15,43,44). Endothelium-dependent vasodilation to a...