Die Bedeutung funktioneller Proteine des sarkoplasmatischen Retikulums für die Calcium-Homöostase der Herzmuskelzelle

Calcium-Ionen sind für die Kontraktionsfähigkeit des Herzens und die elektromechanische Kopplung der Herzmuskelzelle von entscheidender Bedeutung. Die Calcium-Ionen gelangen über spannungsabhängige Calciumkanäle in die Zelle. Dort werden sie unter dem Einfluß spezieller Calcium-regulierender Proteine im sarkoplasmatischen Retikulum gespeichert und bei Bedarf wieder freigesetzt. In der vorliegenden Arbeit wurden Untersuchungen an isolierten Herzmuskelzellen transgener Mäuse durchgeführt, in denen die Menge an Calcium-regulierenden Proteinen, Triadin 1, Junctin, SERCA 2a und des Inhibitor 2 der Phosphatase 1 vergrößert war. Dabei wurde mit Hilfe von Fluoreszenz-Farbstoffen der dynamische intrazelluläre Calcium- Gehalt (Ca2+-Transient) der Zellen gemessen und hinsichtlich seiner Größe und Eigenschaften untersucht. Desweiteren wurden mittels konfokaler Lasermikroskopie lokale Freisetzungen von Calcium-Ionen (Sparks) innerhalb isolierter Herzmuskelzellen gemessen und deren Intensität und zeitlicher Verlauf analysiert

Effect of Ap 4 A, UTP and Salbutamol on Mucociliary Clearance in a Mouse Model of Cystic Fibrosis (in Situ)

ABSTRACT Cystic fibrosis is a life-threatening, wide spread genetic disease diagnosed in 1 to 3000 livebirths of the Caucasian population. Here a mouse model for this disease is described and optimized using the CFTR-channel selective inhibitor CFTR(inh 172). The target parameter was mucociliary clearance measured using microdialysis of the transported fluorescent dye rhodamine in the mouse trachea in situ. The impact of Ap 4 A (diadenosine tetraphosphate) as a potential drug was investigated. Its inhalation was effective at low concentrations; established compounds such as Salbutamol and UTP increased mucociliary clearance as well. Our data show a functioning model of cystic fibrosis and the effectiveness of the newly tested Ap 4 A

Pressure-independent cardiac hypertrophy in mice with cardiomyocyte-restricted inactivation of the atrial natriuretic peptide receptor guanylyl cyclase-A

Cardiac hypertrophy is a common and often lethal complication of arterial hypertension. Atrial natriuretic peptide (ANP) has been postulated to exert local antihypertrophic effects in the heart. Thus, a loss of function of the ANP receptor guanylyl cyclase-A (GC-A) might contribute to the increased propensity to cardiac hypertrophy, although a causative role in vivo has not been definitively demonstrated. To test whether local ANP modulates cardiomyocyte growth, we inactivated the GC-A gene selectively in cardiomyocytes by homologous loxP/Cre-mediated recombination. Thereby we have circumvented the systemic, hypertensive phenotype associated with germline inactivation of GC-A. Mice with cardiomyocyte-restricted GC-A deletion exhibited mild cardiac hypertrophy, markedly increased mRNA expression of cardiac hypertrophy markers such as ANP (fivefold), α-skeletal actin (1.7-fold), and β-myosin heavy chain (twofold), and increased systemic circulating ANP levels. Their blood pressure was 7–10 mmHg below normal, probably because of the elevated systemic levels and endocrine actions of ANP. Furthermore, cardiac hypertrophic responses to aortic constriction were enhanced and accompanied by marked deterioration of cardiac function. This phenotype is consistent with a local function of the ANP/GC-A system to moderate the molecular program of cardiac hypertrophy