To determine the events leading to cardiac fibrosis in aldosterone-salt hypertensive rats, we studied protein and mRNA accumulation of procollagens I and III for 60 days. After 3 and 7 days of treatment systolic pressure was normal, and no histological or biochemical changes were seen in rat hearts. At day 15 arterial pressure was raised (+40%) and left ventricular hypertrophy was +15%. Cardiac examination after hemalun-eosin staining and immunolabeling with anticollagen I and III antibodies showed no structural alterations, but an 83% increase in right ventricular type III procollagen mRNA levels was found. At 30 and 60 days we found progressive cardiac fibrosis, with inflammatory cells, myocyte necrosis, and elevation of both types I and III procollagen mRNA levels in both ventricles. To determine whether aldosterone had effects on Na,K-ATPase that might lead to ionic disturbances and induce myocyte necrosis, we studied the major cardiac Na,K-ATPase isoform genes. Although Na,K-ATPase alpha 1- and beta 1-subunit mRNA levels were elevated in kidney at day 1, neither of these cardiac transcripts nor the specific alpha 2 isoform was altered between 1 and 15 days. These results show that accumulation of procollagen mRNAs occurs before collagen deposition. Cardiac alterations are late and not preceded by changes in Na,K-ATPase cardiac gene expression, precluding a direct modulation of cardiac collagen synthesis and Na,K-ATPase by aldosterone.

The L-type calcium current was investigated in normal and hypertrophied rat ventricular myocytes as a possible cause of the action potential lengthening that has been reported during hypertrophy. Regulation of the calcium current (lCa) by a ,B-adrenergic agonist (isoproterenol) was also analyzed since P-agonist-induced positive inotropy is less marked in hypertrophied

Annexins are a family of 13 proteins known to bind phospholipids (PL) in a Ca(2+)-dependent way. They are ubiquitous proteins and share a similar structure characterized by a conserved C-terminal domain with Ca(2+) binding sites and a variable N-terminal domain. Depending on Ca(2+) concentration, they have been reported to participate in a variety of membrane-related events such as exocytosis, endocytosis, apoptosis and binding to cytoskeletal proteins. They have also been reported to regulate protein activities. This review will focus on annexins in the heart, and particularly on annexins A2, A5, A6 and A7. Annexin A2 has been found in endothelial cells and reported to play a central role in control of plasmin-mediated processes. Annexin A5 is mainly localized in cardiomyocytes. However, it could be relocated to interstitial tissue in ischemic and failing hearts or it could be externalized and exhibit a proapoptotic effect in cardiomyocytes. Annexin A6 is the most abundant annexin in the heart, and has been localized in various cell types including myocytes. Overexpression of annexin A6 has underlined physiological alterations in contractile mechanics leading to dilated cardiomyopathy, whereas knockout has been found to induce faster changes in Ca(2+) transient and increased contractility, suggesting a negative inotropic role for annexin A6. Annexin A7 is expressed in heart and skeletal muscle. In annexin A7 null mutant mice decreases in the force-frequency relationship were observed in adult cardiomyocytes, consistent with regulation of Ca(2+) handling. In conclusion, while annexin A2 was involved in regulation of fibrin homeostasis, alterations in expression and activity of annexins A5, A6 and A7 have been associated with regulation of Ca(2+) handling in the heart, but the target of each annexin has not yet been identified.

SUMMARY:Annexins II, V, and VI belong to a family of Ca 2ϩ -dependent phospholipid-binding proteins that have been involved mainly in signal transduction, differentiation, membrane trafficking events, or binding to the extracellular matrix, or that might be effective as Ca 2ϩ -channels. They are abundant in the mammalian myocardium and might play a role in ventricular remodeling and altered calcium handling during heart failure. To test this hypothesis, we compared the expression and distribution of these annexins in nonfailing (n ϭ 9) and failing human hearts with idiopathic dilated cardiomyopathy (n ϭ 11). Northern blot and slot blot analysis were used to determine the annexin mRNA levels and Western blots were used to quantify the amounts of annexin proteins. Distribution of annexins was studied by immunohistofluorescence labeling and compared with that of a sarcolemmal marker (Na ϩ /K ϩ -ATPase) and of a myofibrillar protein (␣-actinin). We showed that nonfailing hearts contained a higher amount of annexin VI than of annexin V or II (13.5 Ϯ 1.8, 3.7 Ϯ 0.2, and 2.5 Ϯ 0.5 g/mg protein, respectively). In failing hearts, there was a parallel increase in both mRNA and protein levels of annexin II (146% and 132%, p Ͻ 0.05, respectively) and annexin V (152%, p Ͻ 0.01, 147%, p Ͻ 0.005, respectively); the protein level of annexin VI was also increased (117%, p Ͻ 0.05), whereas the increase of its mRNA level was statistically insignificant. We observed a predominant localization of annexin II in interstitium, and of annexins V and VI in cardiomyocytes at the level of the sarcolemma, T-tubules, and intercalated disks in nonfailing hearts, whereas in failing hearts enlarged interstitium contained all three annexins. Furthermore, annexin V staining at the level of cardiomyocytes almost disappeared. In conclusion, we showed that heart failure is accompanied by marked overexpression of annexins II and V, as well as translocation of annexin V from cardiomyocytes to interstitial tissue. The data suggest that annexins may contribute to ventricular remodeling and annexin V to impaired Ca 2ϩ handling in failing heart. (Lab Invest 2000, 80:123-133).

Low-flow ischemia does not induce calcium-regulating protein loss in both adult and senescent hearts. The increase in mRNAs coding for calcium-handling proteins and the impairment of myocardial function which occur at a lesser degree of coronary flow reduction in senescent hearts, indicate a higher vulnerability to low-flow ischemia during aging.

Annexins are characterized by Ca2+-dependent binding to phospholipids. Annexin II mainly participates in cell-cell adhesion and signal transduction, whereas annexins V and VI also seem to regulate intracellular calcium cycling. Their abundance and localization were determined in left ventricle (LV) and right ventricle (RV) from hypertensive guinea pigs, during the transition from compensatory hypertrophy to heart failure. Immunoblot analysis of annexins II, V, and VI revealed an increased accumulation (2.6-, 1.45-, and 2.3-fold, respectively) in LV from hypertensive guinea pigs and no modification in RV. Immunofluorescent labeling of annexins II, V, and VI; of Na+-K+-ATPase; and of sarcomeric α-actinin showed that in control LV and RV, 1) annexin II is present in nonmuscle cells; 2) annexins V and VI are mainly observed in the sarcolemma and intercalated disks of myocytes; 3) annexins II, V, and VI strongly label endothelial cells and adventitia of coronary arteries; and 4) annexin VI is present in the media. At the onset of heart failure, the most striking changes are the increased protein accumulation in LV and the very strong labeling of annexins II, V, and VI in interstitial tissue, suggesting a role in fibrosis development and cardiac remodeling.

Summary The lipid composition of five human breast cancer cell lines T47D, was assessed by proton magnetic resonance spectroscopy (MRS) in whole cells and membraneenriched fractions. The proportions of the three main lipid resonances in 1D spectra were different for each cell line. These resonances included mobile methyl and methylene functions from fatty acids of triglycerides and phospholipids and N-trimethyl from choline of phospholipids. T47D and Materials and methods Cell cultureFive human breast carcinoma cell lines were used: MCF-7, MDA-MB 231, T47D, SKBR3 and ZR-75-l (Engel & Young, 1978). All these cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM, Gibco) supplemented with 10% foetal calf serum, as adherent cells.The cells were mass cultured in the same conditions, in 150 cm2 flasks. The cells from three flasks (107 cells) were harvested at confluency with a rubber policeman scraper and centrifuged at 1,000 r.p.m. for 10 min. For whole cell MRS experiments, the cells were washed three times with 2 ml of phosphate-buffered saline (PBS: KH2PO4 0.2 g 1-, KCI 0.2 g 1-', NaCl 8 g 1-', Na2HPO41.15 g 1-') in deuterium oxide (D20). The final pellet was suspended in PBS/D20 to obtain a final volume of 0.5 ml and placed in a 5 mm MRS tube. For cell membrane preparation, the same number of cells were washed in cool PBS and disrupted with a hypotonic Tris (tris[hydroxymethyl]aminoethane) buffer (0.01 M), followed by a freeze-thaw cycle at -20C; finally, polytron was used three times for 5 s. The resulting homogenate was centrifuged at 1,000 g for 10 min and the supernatant was centrifuged at 47,000 g for 30 min (Beckmann TL 100, rotor TL 100-2). For MRS experiments, the final pellet was suspended in PBS/D20 and 0.5 ml of the suspension was placed in a 5 mm MRS tube. The specific Na+/K+ ATPase activity was determined in the presence or absence of digitoxigenin using a coupled assay method previously described (Noel & Godfraind, 1984

This study indicated for the first time that annexin A5 was externalized at a very early stage of apoptosis and could have a proapoptotic effect in cardiomyocytes.