Nitric oxide synthase mRNA levels correlate with gene expression of angiotensin II type-1 but not type-2 receptors, renin or angiotensin converting enzyme in selected brain areas.

Recent data suggest that there is interaction between peripheral angiotensin II and nitric oxide. However, sparse information is available on the mutual interaction of these two compounds in the brain. The potential intercourse of nitric oxide with brain neuropeptides needs to be substantiated by assessing its local production and gene expression of the synthesizing enzymes involved. The aim of the present study was to evaluate whether the gene expression of brain nitric oxide synthase (bNOS) is related to the sites of gene expression of different components of the rat brain renin angiotensin system (renin, angiotensin converting enzyme (ACE) or angiotensin receptors of AT1 and AT2 subtypes). The levels of corresponding mRNAs were measured and correlated in nine structures of adult rat brain (hippocampus, amygdala, septum, thalamus, hypothalamus, cortex, pons, medulla and cerebellum). As was expected, positive correlation was observed between renin and angiotensin-converting enzyme mRNAs. Moreover, a significant correlation was found between brain NO synthase and AT1 receptor mRNAs, but not with mRNA of the AT2 receptor, ACE and renin. Parallel distribution of mRNAs coding for bNOS and AT1 receptors in several rat brain structures suggests a possible interaction between brain angiotensin 11 and nitric oxide, which remains to be definitely demonstrated by other approaches.

Effect of nicotinic acid adenine dinucleotide phosphate on ryanodine calcium release channel in heart.

Nicotinic acid adenine dinucleotide phosphate (NAADP), a molecule derived from nicotinamide adenine dinucleotide phosphate (NADP+), is a recently identified nucleotide that activates Ca2+ release from intracellular stores in invertebrate eggs and in mammalian cells. NAADP could function as an intracellular messenger for mobilizing internal Ca2+ stores, however the targets and nature of NAADP-induced Ca2+ release are unknown. We report here that NAADP (3-10 microM) induces Ca2+ release from rat heart microsomes and that NAADP (1-10 microM) activates single ryanodine receptor/calcium release channels (RyR2) from dog heart incorporated into bilayer lipid membranes. The results indicate that NAADP may play a role in cardiac excitation-contraction coupling by acting on RyR2 channels.

Identification of type 1 IP(3) receptors in the rat kidney and their modulation by immobilization stress.

Inositol 1,4,5-trisphosphate receptor (IP(3)-receptor) is a calcium channel, transporting calcium from intracellular stores to the cytoplasm. In kidney, IP(3)-receptors are involved in the signal transduction of various hormones. In our work we studied the effect of immobilization stress on the IP(3)-receptor's protein content in renal cortex and the medulla of normotensive and hypertensive rats. We detected both mRNA and type 1 IP(3)-receptor protein in medulla, but not in renal cortex. We found that this receptor was approximately twice as abundant in normotensive as in genetically hypertensive rat kidney. Immobilization stress decreased the amount of type 1 IP(3)-receptor in the renal medulla of normotensive rats approximately five times, while no effect due to single and/or repeated stress was observed in the renal medulla of spontaneously hypertensive rats. The results indicate that expression of type 1 IP(3)-receptor in renal medulla is modulated by hypertension and immobilization stress.

[Structure and function of selected Ca(2+) transport systems in cardiac cells]. / Struktúra a funkcia vybraných Ca(2+)-transportných systémov v srdcových bunkách.

Transport systems, which transfer calcium across the plasma membrane or from the intracellular stores belong to important modulators of the intracellular calcium concentration. It is well known that the maintenance of the calcium homeostasis becomes the basis of the proper function of the heart muscle and its impairment leads to the development of the pathophysiological changes which may end in the cell death. Diversity of the calcium transport systems is given not only by their function (transfer of calcium across the plasma membrane in both direction) but also by their location (in the plasma membrane or in membranes of the intracellular stores). This review summarizes the current knowledge about the structure and function of selected calcium systems in the cardiac cells. We focused mainly on the L-type calcium channel, which is involved in the process of excitation and contraction coupling, and on the Na/Ca exchanger, which is considered to be an important system for the calcium extrusion from the heart cells.

Increased expression of the Na(+)/Ca(2+) exchanger in the rat heart after immobilization stress is not induced by cortisol.

Calcium homeostasis is crucial for the proper function of cardiac cells. Since the Na(+)/Ca(2+) exchanger is an important modulator of calcium homeostasis especially in the heart, the objective of this study was to investigate the effect of immobilization stress on the high capacity Na(+)/Ca(2+) exchanger in rat heart ventricles and atria. Repeated immobilization stress increased both the mRNA and the protein level and the activity of the Na(+)/Ca(2+) exchanger in the left, but not the right ventricle of rat heart. Since corticosterone is rapidly increased during the stress stimulus, it might be assumed that mRNA of the Na(+)/Ca(2+) exchanger is increased through a glucocorticoid responsive element. However, we have found that cortisol did not change the Na(+)/Ca(2+) exchanger at the mRNA or protein levels. These results clearly show that this effect of stress is not mediated via cortisol.

Study of in vitro conditions modulating expression of MN/CA IX protein in human cell lines derived from cervical carcinoma.

In an effort to better understand the biological significance of MN/CA IX human tumor-associated protein, we have investigated its expression in human cervical carcinoma cell lines in vitro. SiHa cells that naturally express MN/CA IX were used as a model for expression study at the protein level. In addition, we have transfected MN/CA9 gene-negative but transcription-competent C33A cells with a plasmid carrying CAT reporter gene under a control of MN/CA9 promoter. By this way, we have generated a stable cell line C33A/MNP-CAT that was employed in analysis of MN/CA9 regulation at the level of promoter activity as estimated by CAT protein abundance. For the purpose of our study, we have chosen experimental conditions relevant to growth characteristics and phenotypic features of malignantly transformed cells. Both the level of MN/CA IX protein and the gene promoter activity were found to be substantially elevated either in culture of high density or when the adherent carcinoma cells grew in suspension, but were not markedly affected by diminished serum concentration and in the cell cycle progression. These observations support the involvement of MN/CA IX protein in aberrant cell-cell and cell-matrix interactions that facilitate loss of contact inhibition and anchorage independence of cancer cells.