Therapeutic approach for metabolic disorders and infertility in women with PCOS.

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder affecting 5-10% of women of reproductive age. It generally shows with oligo/amenorrhea, anovulatory cycles, clinical o biochemical hirsutism, polycystic ovaries and, in a significant percentage of cases, insulin resistance. PCOS is defined as a multifactorial pathology, determined by the association of many factors: genetic, endocrine and environmental. The first and most effective treatment of PCOS is to change life-style and lose weight. The use of oral contraceptives has been shown effective in reducing acne and hirsutism and regulates the menstrual cycle. For women with severe hirsutism, the addition of antiandrogens to estrogen-progestin therapy has significantly improved the results. In cases of anovulatory infertility, the drug of first choice is clomiphene citrate, followed by low-dose gonadotropins. Recently, insulin-sensitizing drugs have been widely prescribed for PCOS patients. They are particularly effective in reducing insulin resistance and improving ovulatory performance. Besides insulin-sensitizing drugs, natural substances, such as inositol, seems to have good efficacy, similar to metformin with fewer side effects. New substances that could be used include statins and natural statins, such as monakolin, alone or combined with myo-inositol. These substances do not have side effects and greatly reduce the hyperandrogenic component in these patients.

Genetic, hormonal and metabolic aspects of PCOS: an update.

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder affecting 5-10 % of women of reproductive age. It generally manifests with oligo/anovulatory cycles, hirsutism and polycystic ovaries, together with a considerable prevalence of insulin resistance. Although the aetiology of the syndrome is not completely understood yet, PCOS is considered a multifactorial disorder with various genetic, endocrine and environmental abnormalities. Moreover, PCOS patients have a higher risk of metabolic and cardiovascular diseases and their related morbidity, if compared to the general population.

Control of carbapenemase-producing Klebsiella pneumoniae: a region-wide intervention.

Starting in 2010, there was a sharp increase in infections caused by Klebsiella pneumoniae resistant to carbapenems in the Emilia-Romagna region in Italy. A region-wide intervention to control the spread of carbapenemase-producing K. pneumoniae (CPKP) in Emilia-Romagna was carried out, based on a regional guideline issued in July 2011. The infection control measures recommended to the Health Trusts (HTs) were: phenotypic confirmation of carbapenemase production, active surveillance of asymptomatic carriers and contact isolation precautions for carriers. A specific surveillance system was activated and the implementation of control measures in HTs was followed up. A significant linear increase of incident CPKP cases over time (p<0.001) was observed at regional level in Emilia-Romagna in the pre-intervention period, while the number of cases remained stable after the launch of the intervention (p=0.48). Considering the patients hospitalised in five HTs that provided detailed data on incident cases, a downward trend was observed in incidence after the release of the regional guidelines (from 32 to 15 cases per 100,000 hospital patient days). The spread of CPKP in Emilia-Romagna was contained by a centrally-coordinated intervention. A further reduction in CPKP rates might be achieved by increased compliance with guidelines and specific activities of antibiotic stewardship.

Protein modification as oxidative stress marker in follicular fluid from women with polycystic ovary syndrome: the effect of inositol and metformin.

PURPOSE: The purpose of this study was to evaluate the oxidative stress status (OS) of follicular fluid (FF) and the oocyte quality in women with polycystic ovary syndrome (PCOS) undergoing different ovarian stimulation protocols. METHODS: FF samples were collected after gonadotropin administration in association or not with metformin or D-chiro-inositol (DCI). OS status was then evaluated by checking the follicular fluid protein oxidation profile after specific labeling of aminoacidic free-SH groups, and two-dimensional electrophoresis followed by qualitative and semiquantitative analysis. Oocyte quality was assessed by international morphological criteria. RESULTS: Our data indicated that both treatments, even if to different extent, recovered a significantly high level of free-SH groups in FF proteins of PCOS women clearly indicating a decrease of OS level with respect to that found in FF samples from gonadotropins alone treated women. A higher number of good quality MII oocytes was also observed in DCI (P < 0.05) or metformin (P < 0.05) study groups in comparison to untreated control group. CONCLUSION: A natural supplement and a drug both showed a statistically significant positive effect on follicular milieu by decreasing the oxidative damage on FF proteins, as well as in recovering good quality oocytes.

[Evaluation of a new association between insulin-sensitizers and α-lipoic acid in obese women affected by PCOS]. / Valutazione di una nuova associazione tra insulino-sensibilizzanti e acido α-lipoico in donne obese affette da PCOS.

AIM: Polycystic ovary syndrome (PCOS) is a multifactorial pathology affecting 7-10% of the female population. Usually occurs with oligo/amenorrhea, anovulation, hirsutism, polycystic ovaries. Hyperinsulinemia associated with insulin resistance has been causally linked to all features of the syndrome. It has been demonstrated that by reducing hyperinsulinemia, in particular with the administration of metformin, insulin-lowering agents might improve endocrine and reproductive abnormalities in PCOS patients. METHODS: Original association between myo-inositol and alpha-lipoic acid, has recently been successfully administered in women with PCOS. The α-lipoic acid is a powerful natural antioxidant and an enzyme cofactor of the mitochondrial respiratory chain, is found to be a substance capable of improving glycemic control in patients with type II diabetes. In our study we compared two groups: group A, treated with metformin (3 g) and group B treated with metformin (1.7 g), myo-inositol and alpha-lipoic acid. RESULTS: The results of this study demonstrated a good efficacy of both treatments, although in the group treated with the combination of metformin/myo-inositol/alpha-lipoic acid improvement in hyperandrogenism, BMI and HOMA index were significantly better. CONCLUSION: Thus, the association metformin/myo-inositol/alpha-lipoic acid represents an excellent therapy choice to suggest to those obese women affected by PCOS who do not want to take hormones and neither to have any severe side effect.

[Evaluation of the myo-inositol-monacolin K association on hyperandrogenism and on the lipidic metabolism parameters in PCOS women]. / Valutazione dell'associazione myo-inositolo-monacolina K sull'iperandrogenismo e sui parametri del metabolismo lipidico in donne con PCOS.

AIM: Polycystic ovary syndrome (PCOS) is a multifactorial pathology affecting 5-10% of the female population. Usually occurs with oligo/amenorrhea, anovulation, hirsutism, polycystic ovaries. Hyperinsulinemia associated with insulin resistance has been causally linked to all features of the syndrome. It has been demonstrated that by reducing hyperinsulinemia, in particular with the administration of metformin, insulin-lowering agents might improve endocrine and reproductive abnormalities in PCOS patients. METHODS: A new molecule with insulin-sensitizing properties, myo-inositol, has recently been successfully administered in women with PCOS. New associations between natural substances like myo-inositol and other components have been proposed to improve the therapeutical efficacy. Among these substances, the monacolin K, a natural statin appeared to have important actions in cholesterol synthesis. In this article we study the effect of inositol alone and the association between myo-inositol and monacolinin K in the treatment of PCOS with insulin resistance, menstrual irregularities and hirsutism. RESULTS AND CONCLUSION: The results of this study demonstrated a good efficacy of both treatments, although in the group treated with the combination of myo-inositol/monacolin K improvement in lipids and hyperandrogenism were significantly better.

[Evaluation of the treatment with D-chiro-inositol on levels of oxidative stress in PCOS patients]. / Valuzione del trattamento con D-chiro-inositolo dui livelli di stress ossidativo nelle pazienti con PCOS.

AIM: Recent studies on the pathophysiology of infertility have shown that oxidative stress (OS) can be one of the causal factors. The OS is, by definition, an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense systems. It seems that oxidative stress plays an important role in almost all phases of human reproduction. In fact, ROS are involved in the modulation of a large spectrum of reproductive functions such as oocyte maturation, ovarian steroidogenesis, corpus luteum functions and are involved in the processes of fertilization, embryo development and pregnancy, but also in some diseases that cause infertility. Polycystic ovary syndrome (PCOS) has recently been associated with increased oxidative stress, often put in relation to the syndrome's typical metabolic disorder. Inositol is an intracellular mediator of insulin, currently much used as a therapeutic agent in PCOS. While its main action takes place via insulin sensitization, little is known about the possible effects of other disorders, such as oxidative stress, associated with PCOS. The purpose of this study was therefore to assess the effect of D-chiro-inositol on the state of oxidative stress in the follicular fluid of women with PCOS. METHODS: Follicular fluids were obtained from women who have turned to the Center for Diagnosis and Treatment of Sterility of Obstetrics and Gynecology of the University Hospital of Siena and Modena diagnosed with PCOS. The women were treated with D-chiro-inositol (500 mg x 2 per day) for 3 months before being subjected to cycles of in vitro fertilization (IVF). The state of oxidative stress was measured by marking of free thiol groups of proteins in the follicular fluid with 3-(N-Maleimidopropionyl)-biocytin. RESULTS: In our study we obtained a lesser presence of free thiol protein groups equal to 77.8% in the follicular fluid of women with PCOS not treated with D-chiro-inositolo, compared to patients who instead have carried out such treatment. CONCLUSION: These results suggest that in PCOS women there is an increase of the oxidation of thiol groups of proteins follicular, correlated to a progressive increase of the oxidative stress and that the administration of D-chiro-inositol in patients with this disease seems to reduce the oxidation of thiol groups.

Metformin doses and body mass index: clinical outcomes in insulin resistant polycystic ovary syndrome women.

OBJECTIVE: PCOS is the most common endocrinopathy among reproductive age women. Approximately 60% of PCOS women have insulin resistance. While the efficacy of metformin in reducing insulin resistance and decreasing androgen level has been widely validated, there is no agreement on the dose of metformin to be used. PATIENTS AND METHODS: Prospective non-randomized cohort study of 108 insulin resistant, overweight and obese PCOS women, aged between 22 and 35 years. All patients received 1500 mg of metformin (500 mg x 3 times/day) for the first 6 months. At the end of this period, the patients' HOMA index was evaluated. In subjects, who did not demonstrate normalization of the HOMA index, the dose was increased to 2500 mg/day (500 mg at breakfast and 1000 mg at lunch and dinner) for additional 6 months. The hormonal blood profile, fasting insulin and fasting glucose levels, HOMA index, anthropometric assessment, pelvic ultrasound, FAI index and cholesterol were evaluated. RESULTS: Overall results showed a good response to metformin therapy in insulin-resistant PCOS patients with BMI >25, while in patients with higher BMI (31.15 ± 0.40), no normalization of HOMA was found. At the higher dose of metformin, obese patients achieved a good response to therapy, with improvement in BMI, menstrual pattern, cholesterol levels and hyperandrogenism. CONCLUSIONS: Our results demonstrate a correlation between the required dose of metformin, BMI and hyperandrogenism. The dose of metformin should be adjusted to patients' BMI in order to obtain significant results in terms of clinical, metabolic and hormonal responses.

Natural molecules for the therapy of hyperandrogenism and metabolic disorders in PCOS.

OBJECTIVE: Polycystic ovary syndrome (PCOS) is the most common endocrinopathy of women of reproductive age and a complex endocrine condition, due to its heterogeneity and uncertainty about its etiology. However, PCOS is also associated with other metabolic abnormalities such as insulin resistance, impaired glucose tolerance, and diabetes. There are few medications that are approved for the most common symptoms of PCOS, leading to the off-label use of medications that were approved for other indications. One of the most common medications being used off label for PCOS is metformin. Research of other effective therapeutic options has included the utility of inositol. PATIENTS AND METHODS: A systematic literature search of PubMed was performed using the following combination of terms: 'PCOS', 'hyperandrogenism' 'inositol', 'natural molecules'. Only papers published between 2000 and 2016 were included in our analysis. The present review analyzes all aspects of the choice of natural molecules in the treatment of hyperandrogenism and metabolic disorders in PCOS women. RESULTS: The rationale underlying the use of inositols as a therapeutic application in PCOS derives from their activities as insulin mimetic agents and their salutary effects on metabolism and hyperandrogenism without side effects. CONCLUSIONS: In this review will discuss the role of a number of natural associations between inositol and different substances in the treatment of hyperandrogenic symptoms in PCOS women.

[Metabolic acidosis in patients with chronic kidney diseases: why and when to treat it?]. / Acidosi nell'insufficienza renale: perche' e quando trattarla.

Metabolic acidosis is a common complication in patients with advanced chronic renal diseases and dialytic treatments are unable to correct it completely. In hemodialysis (HD) patients, severe metabolic acidosis is associated with an increased risk of death. Evidence from several experimental studies suggests that even mild metabolic acidosis is associated with systemic effects. Acidosis is implicated in endocrine changes and has negative repercussions on bone and protein metabolism. In addition, recent observations suggest that acidosis triggers inflammation and accelerates the progression of chronic kidney diseases. As a contradictory finding, acidosis can reduce circulating leptin. Clinical studies on the nutritional effects of metabolic acidosis correction have shown mildly favorable effects. Taking into account the systemic effects of metabolic acidosis it is suggested that even mild metabolic acidosis is corrected. However, the new findings concerning the systemic effects of acidosis must be evaluated in controlled trials.

Polycystic ovary syndrome (PCOS) and hyperandrogenism: the role of a new natural association.

AIM: Polycystic ovary syndrome (PCOS) affects 5-10% of women of childbearing age and manifests itself through oligomenorrhea, anovulation, hirsutism, micro-polycystic ovaries. Insulin resistance is a characteristic of PCOS patients and is more pronounced in obese patients. Insulin resistance and consequent hyperinsulinemia are related to many aspects of the syndrome such as hyperandrogenism, reproductive disorders, acne and hirsutism. In the long-term it may increase the risk of cardiovascular disease and negatively affect lipid profile and blood pressure. Changes in lifestyle and diet can partially improve these aspects. The use of insulin-sensitizing drugs such as metformin often normalises the menstrual cycle, improving hyperandrogenism and, subsequently, the response to ovulation induction therapies. New molecules have recently been marketed, that produce the same results, but without the side-effects. One of these is myo-inositol, a new insulin-sensitizing molecule which has been successfully administered to women suffering from PCOS. Associations between inositol and other compounds that can increase the therapeutic effect have been proposed. Of these, we found to be interesting the association with monacolin K, a natural statin that reduces cholesterol levels starting point of the synthesis of steroids, including androgens, and lipoic acid, known for its anti-inflammatory, antioxidant and insulin-sensitizing activity. We decided to assess the efficacy of the product. METHODS: We recruited 30 women aged between 24 and 32 years suffering from PCOS with insulin resistance, HOMA index>2.5 and no other endocrine diseases. The following were assessed: Body Mass Index (BMI), characteristics of menstrual cycles, lipid profile (total cholesterol, and HDL), androgens (total testosterone and androstenedione). The patients were also assessed for the degree of hirsutism using the Ferriman-Gallwey Score>8. The subjects were divided into two groups: Group A, treated with an association of 1 g myo-inositol, 5 mg monacolin K and 400 mg lipoic acid for 6 months; Group B, treated with a double dosage of 2 g myo-inositol, 10 mg monacolin K, 800 mg lipoic acid for 6 months. RESULTS: The results have shown good efficacy of both dosages, although women treated with a double dosage of myo-inositol, monacolin K and lipoic acid showed a significantly greater improvement in terms of lipid parameters and those connected with hyperandrogenism. CONCLUSION: This new myo-inositol, monacolin K and lipoic acid association contains appropriate substances to contrast various etiopathogenic elements responsible for the onset of PCOS and the symptoms of hyperandrogenism and dyslipidemia related to it.

[Evaluation of the efficacy of a new nutraceutical product in the treatment of postmenopausal symptoms]. / Valutazione dell'efficacia di un nuovo preparato nutraceutico nel trattamento dei disturbi delle donne in postmenopausal.

The onset of vasomotor symptoms in postmenopausal women represents the beginning of a hard period from the emotional point of view which involves some of the most important neurotransmitters. Hot flushes and insomnia associated with a state of anxiety that affect postmenopausal women are included in an index known as the Kupperman Index. The use of nutraceuticals in Italy is increasingly widespread, and only 6-8% of women currently choose to take hormone replacement therapy. The action of these natural supplements primarily depends on the selection of substances and the dose of each single ingredient. Moreover, it also depends on the range of vasomotor symptoms (from mild to moderate/severe). The aim of this study was to test the action of a new product without phytoestrogens containing Cimicifuga racemosa, chasteberry (Vitex agnus-castus), hyaluronic acid, zinc and ginger (ElleN®) in two different groups of women: one with mild and the other with moderate/severe menopausal symptoms. All women received a dose of one tablet per day of ElleN® for three months. Results showed a significant reduction in the Kupperman Index in both groups. The treatment was particularly effective against hot flushes associated with night insomnia and anxiety. The product was well tolerated, did not cause any side effects, and none of the subjects dropped out of the study. In conclusion, it can be stated that the supplement evaluated in the present study is able to reduce moderate/severe menopause symptoms.

Liver and brain thiamin depletion and neurologic signs in pigeon athiaminosis.

Blood pyruvate and free and phosphorylated thiamin contents of liver and brain were measured in pigeons during diatary thiamin deficiency. Neurologic signs (opisthotonus and ataxia) appeared in the course of thiamin deficiency or did not appear at all during the entire athiaminosis period. As compared to respective controls, which never exhibited any neurologic abnormalities in spite of thiamin deficiency, the symptomatic animals had a higher pyruvate level in blood and a significantly lower phosphorylated thiamin content in both liver and brain. A hypothesis on relationship between phosphorylated thiamin content of liver and brain and occurence of nervous symptoms was expressed.

Thyroid hormone regulation of MHC isoform composition and myofibrillar ATPase activity in rat skeletal muscles.

Myosin heavy chain (MHC) isoform composition and Ca2+ Mg2+ dependent ATPase activity were determined in myofibrils prepared from skeletal muscles (diaphragm, soleus, plantaris and tibialis anterior) of euthyroid (C), hypothyroid (Tx) and hyperthyroid (T3) rats. Direct comparison between T3 and Tx gave an indication of the maximal effect of thyroid hormones. Significant differences in MHC-1 and MHC-2B proportions and in ATPase activity were found in all muscles. The difference in MHC-2A/X proportion was significant only in soleus, diaphragm and plantaris. When T3 and C were compared, significant variations in MHC isoform composition were found only in plantaris and diaphragm. The comparison between Tx and C showed significant differences in MHC isoform distribution and in ATPase activity in most muscles. The differences in ATPase activity among muscles and among thyroid states were consistent with those in MHC isoform distribution. From the correlations between ATPase activity and MHC isoform distribution the enzymatic activities of individual MHC isoforms were calculated. The results indicate that MHC isoform distribution is controlled by thyroid state in all skeletal muscles and that changes in MHC isoforms distribution are accompanied by proportional changes in ATPase activity.

[Combination inositol and glucomannan in PCOS patients]. / Valutazione dell'associazione inositolo-glucomannano nel trattamento di donne affette da PCOS.

AIM: Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies of the reproductive age in women. PCOS is an endocrine-metabolic disorder characterized by insulin resistance. Aim of the study was to evaluate the efficacy of natural substances such as inositol and glucomannan, and their combination in reducing glucose levels and improving insulin sensitivity in PCOS patients. METHODS: Forty women with clinical and endocrinological signs of PCOS were enrolled in the study and divided into three groups, including ten women each. The three groups were respectively treated with the combination inositol and glucomannan (A group), inositol (B group), glucomannan (C group) for a period of 3 months. Plasma levels of glucose and insulin were evaluated before and after treatment in our laboratory. RESULTS: There was a reduction in blood glucose and insulin levels, with particular significance in the group treated with the combination of inositol-glucomannan. CONCLUSION: Present results show that the association-inositol glucomannan may represent a good therapeutic strategy in the treatment of PCOS women with insulin resistance.

Peripheral tissue release of interleukin-6 in patients with chronic kidney diseases: effects of end-stage renal disease and microinflammatory state.

To examine if uremia influences muscle interleukin-6 (IL-6) metabolism we studied the exchange of IL-6 across the forearm in 16 patients with chronic kidney disease (CKD) (stages 3 and 4), in 15 hemodialysis (HD)-treated end-stage renal disease (ESRD) patients (n=15), and in six healthy controls. In addition, we performed an analysis of both IL-6 protein and IL-6 mRNA expression in muscle of CKD (stage 4) patients showing evidence of inflammation and in controls. A release of IL-6 from the forearm was observed in patients with elevated IL-6 plasma levels. Arterial IL-6 was directly related to released IL-6 (r=0.69; P<0.004) in HD patients. Both IL-6 protein and IL-6 mRNA expression were increased in muscle of inflamed CKD patients vs controls (P<0.05). Although muscle net protein balance was similar in all patients, it was significantly more negative in HD patients with high than in those with low IL-6 plasma levels (P<0.05). In addition, net protein balance was related to the forearm release of IL-6 in HD patients only (r=0.47; P<0.038). These data demonstrate that IL-6 expression is upregulated in muscle, and that muscle tissue, by releasing this cytokine, may contribute to the inflammatory response in HD patients. The release of IL-6 from peripheral tissues is associated with an increase in muscle protein loss in HD patients, suggesting that muscle release of IL-6 is linked to protein catabolism in these patients. The release of IL-6 from peripheral tissues may act as a signal for the inflammatory response and contribute to functional dysregulation in uremia.

Oxygen availability, dietary restriction and transport of glucose 3-O-methylglucose and fructose in the isolated small intestine of rat.

The influences of PO2 of the incubating medium on glucose, 3-O-methylglucose and fructose transport by everted small intestine sacs in semistarved and rats fed ad libitum (controls) was investigated. Moreover fructose uptake and conversion to glucose by intestinal sacs was also studied. The results showed that intestinal sacs from semistarved rats transported larger amounts of glucose and 3-O-methylglucose and took up more fructose than controls, when PO2 of the incubating medium was 150 mm Hg. There was greater fructose conversion to glucose in the intestine of semistarved rats than in controls at all PO2's considered. The greater functional capacity of intestinal tissue of semistarved rats in comparison to controls has been related to larger O2 availability in their intestinal wall.

Effects of amrinone on shortening velocity and force development in skinned skeletal muscle fibres.

The effects of amrinone were studied on single skinned fibres isolated from rat hindlimb muscles. In each fibre a force-velocity relation was determined during maximal calcium activation (pCa = 4.45) in control conditions and in the presence of amrinone. The MgATP concentration was 3.93 mM, close to the physiological value. After the experiment the fibre was classified as fast or slow on the basis of its reactivity with anti-myosin monoclonal antibodies. In fast fibres amrinone (3 mM) potentiated isometric tension (Po) by 13.8 +/- 2.9% (n = 13), reduced maximum shortening velocity (Vmax) by 32.6 +/- 3.2% and the curvature of the force-velocity relation (a/Po) was increased by 98.9 +/- 46.0%. All these effects were less pronounced in slow fibres, where Vmax was reduced only by 11.4 +/- 3.6 (n = 16). The effects of amrinone (0.3-6 mM) on the ATPase activity of myofibrils and myosin prepared from fast (tibialis anterior) and slow (soleus) rat skeletal muscles were studied. Amrinone was found to depress Ca-Mg dependent ATPase activity of myofibrillar preparations of the tibialis anterior (up to 16.6 +/- 2%) and, to a lesser extent, of the soleus (up to 7.2 +/- 1.2%). On the contrary, Ca-stimulated myosin ATPase activity was significantly increased by amrinone in myosin preparations from the tibialis anterior. Experiments were carried out to test whether amrinone (3 mM) might affect the sensitivity of the contractile system to MgATP concentration ([MgATP]). The results obtained showed that (1) the [MgATP] value at which isometric tension reached its maximum was shifted by amrinone from 0.1 mM to 0.3 mM, (2) the slope of the negative relation between [MgATP] and a/Po was made more steep by amrinone, and (3) the Km of the hyperbolic relation between [MgATP] and Vmax was increased from 0.39 to 1.71 mM by amrinone, thus indicating a reduced affinity of myosin for MgATP. These results are in accordance with the hypothesis that amrinone exerts a direct effect on the contractile mechanism.

Maximum speed of shortening and ATPase activity in atrial and ventricular myocardia of hyperthyroid rats.

The kinetic properties of the myofibrillar system of atrial and ventricular myocardia of hyperthyroid rats were analyzed by determining ATPase activity and maximum shortening velocity. Hyperthyroidism was induced by daily subcutaneous injections of triiodothyronine (0.2 mg/kg body wt) for 2 wk. The treatment induced a marked atrial and ventricular hypertrophy and, in ventricular myocardium, an isomyosin shift toward a homogeneous V1 composition. Skinned trabeculae and purified myofibrils were prepared from atrial and ventricular myocardia. Enzymatic assays on the myofibrils showed that both Ca-stimulated ATPase activity and Ca-Mg-dependent ATPase activity had equal values in atrial and ventricular myocardia. In skinned trabeculae during maximal Ca activations, force-velocity curves were determined by load-clamp maneuvers, and unloaded shortening velocity (Vo) was obtained with the slack-test method. Both maximum shortening velocities extrapolated from the force-velocity curves (Vmax) and Vo were significantly higher (+68 and +52%, respectively) in atrial than in ventricular preparations. Developed tension was significantly greater in ventricular preparations. Maximum power output was not significantly different. Previous findings (V. Cappelli, R. Bottinelli, C. Poggesi, R. Moggio, and C. Reggiani. Circ. Res. 65: 446-457, 1989) had led to the conclusion that variations in ATPase activity and shortening velocity of ventricular myocardium can be accounted for by changes in isomyosin composition. In this light, the present results suggest that 1) ATPase activity is equal in atrial and ventricular myocardia as the two tissues contain the same myosin heavy chain isoform, 2) the difference in maximum speed of shortening between atrium and ventricle might be due to the presence of tissue-specific isoforms of myosin light chains.