Abstract-During pregnancy, the heart develops a reversible physiological hypertrophic growth in response to mechanical stress and increased cardiac output; however, underlying molecular mechanisms remain unknown. Here, we investigated pregnancy-related changes in heart structure, function, and gene expression of known markers of pathological hypertrophy and cell stretching in mice hearts. In late pregnancy, hearts show eccentric hypertrophy, as expected for a response to volume overload, with normal left ventricular diastolic function and a moderate reduction in systolic function. Pregnancy-related physiological heart hypertrophy does not induce expression changes of known markers of pathological hypertrophy like: ␣-and ␤-myosin heavy chain, atrial natriuretic factor, phospholamban, and sarcoplasmic reticulum Ca 2ϩ -ATPase. Instead, it induces the remodeling of Kv4.3 channel and increased c-Src tyrosine kinase activity, a stretch-responsive kinase. Cardiac Kv4.3 channel gene expression was downregulated by Ϸ3-to 5-fold, both at the mRNA and protein levels, and was paralleled by a reduction in transient outward K ϩ currents, a longer action potential and by prolongation of the QT interval. Downregulation of cardiac Kv4.3 transcripts was mimicked by estrogen treatment in ovariectomized mice, and was prevented by the estrogen receptor antagonist ICI 182,780. c-Src activity increased by Ϸ2-fold in late pregnancy and after estrogen treatment. We propose that, in addition to mechanical stress, the rise of estrogen toward the end of pregnancy contributes to pregnancy-related heart hypertrophy by increased c-Src activity and that the rise of estrogen is one factor that down regulates cardiac Kv4.3 gene expression providing a molecular correlate for a longer QT interval in pregnancy. Key Words: heart hypertrophy Ⅲ pregnancy Ⅲ estrogen Ⅲ I to Ⅲ Kv4.3 channel D uring pregnancy, the heart undergoes hypertrophic growth to compensate for the increased cardiac output. Cardiac hypertrophy has been defined as an increase in cardiomyocyte size that can be beneficial and adaptive (physiological) or a maladaptive (pathophysiological) phenomenon to compensate for the hemodynamic stress resulting from pressure or volume overloads. Pressure overload induces concentric hypertrophy characterized by wall thickening without significant chamber enlargement. Volume overload, as in pregnancy, induces eccentric hypertrophy characterized by chamber enlargement with a proportional change in wall thickness. 1 Physiological hypertrophy is reversible and occurs during maturation, pregnancy, and exercise without morbid effects on cardiac function. [2][3][4] Despite the growing knowledge of the molecular changes that can occur during pathological heart hypertrophy, 1 the underlying molecular mechanisms of pregnancy-related heart hypertrophy are unknown.In pathological heart hypertrophy, expression of a set of genes has been reported to be altered and, therefore, can be used as markers for this class of hypertrophy. Examples are, ␣-, ␤-myosin heavy c...

Drosophila melanogaster is a valuable model system for the neural basis of complex behavior, but an inability to routinely interrogate physiologic connections within central neural networks of the fly brain remains a fundamental barrier to progress in the field. To address this problem, we have introduced a simple method of measuring functional connectivity based on the independent expression of the mammalian P2X2 purinoreceptor and genetically encoded Ca 2ϩ and cAMP sensors within separate genetically defined subsets of neurons in the adult brain. We show that such independent expression is capable of specifically rendering defined sets of neurons excitable by pulses of bath-applied ATP in a manner compatible with high-resolution Ca 2ϩ and cAMP imaging in putative follower neurons. Furthermore, we establish that this approach is sufficiently sensitive for the detection of excitatory and modulatory connections deep within larval and adult brains. This technically facile approach can now be used in wild-type and mutant genetic backgrounds to address functional connectivity within neuronal networks governing a wide range of complex behaviors in the fly. Furthermore, the effectiveness of this approach in the fly brain suggests that similar methods using appropriate heterologous receptors might be adopted for other widely used model systems.

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The process of parturition involves the complex interplay of factors that change the excitability and contractile activity of the uterus. We have compared the relative gene expression profile of myometrium from rats before parturition (21 days pregnant) and during delivery, using high-density DNA microarray. Of 8,740 sequences available in the array, a total of 3,782 were detected as present. From the sequences that were significantly altered, 59 genes were upregulated and 82 genes were downregulated. We were able to detect changes in genes described to have altered expression level at term, including connexin 43 and 26, cyclooxygenase 2, and oxytocin receptor, as well as novel genes that have been not previously associated with parturition. Quantitative real-time PCR on selected genes further confirmed the microarray data. Here we report for the first time that aquaporin5 (AQP5), a member of the aquaporin water channel family, was dramatically downregulated during parturition (approximately 100-fold by microarray and approximately 50-fold by real-time PCR). The emerging profile highlights biochemical cascades occurring in a period of approximately 36 h that trigger parturition and the initiation of myometrium reverse remodeling postpartum. The microarray analysis uncovered genes that were previously suspected to play a role in parturition. This regulation involves genes from immune/inflammatory response, steroid/lipid metabolism, calcium homeostasis, cell volume regulation, cell signaling, cell division, and tissue remodeling, suggesting the presence of multiple and redundant mechanisms altered in the process of birth.

The localization of sarcolemmal proteins within the membrane can have a dramatic effect on excitation-contraction coupling. We examine the localization of the Na + -Ca 2+ exchanger, the dihydropyridine receptor, and other proteins involved in excitation-contraction coupling in rat heart using biochemical and immunolocalization techniques. Specifically, we assess the distribution of proteins within the lipid raft fraction of the sarcolemma. We find that the distribution of proteins in lipid raft fractions is very dependent on the solubilization technique. A common technique using sodium carbonate/pH 11 to solubilize non-lipid raft proteins was inappropriate for use with sarcolemmal membranes. Use of Triton X-100 was more efficacious as a solubilization agent. A large majority of the Na + -Ca 2+ exchanger, Na + /K + -ATPase, and plasma membrane Ca 2+ pump are not present in lipid rafts. In contrast, most adenosine A 1 receptors and dihydropyridine receptors were in lipid raft fractions. Most of the adenosine A 1 receptors could be co-immunoprecipitated with caveolin indicating a localization to caveolae (a subclass of lipid rafts). In contrast, the dihydropyridine receptors could not be co-immunoprecipitated with caveolin. Most biochemical data were confirmed by high resolution immunolocalization studies. Using correlation analysis, only a small fraction of the Na + -Ca 2+ exchangers colocalized with caveolin whereas a substantial fraction of dihydropyridine and adenosine A 1 receptors did colocalize with caveolin. The most pertinent findings are that the Na + -Ca 2+ exchanger and the dihydropyridine receptor are in separate sarcolemmal subcompartments. These spatial relationships may be relevant for understanding excitation-contraction coupling.