Hypertrophy, increased ejection fraction, and reduced Na-K-ATPase activity in phospholemman-deficient mice.

Phospholemman (FXYD1), a 72-amino acid transmembrane protein abundantly expressed in the heart and skeletal muscle, is a major substrate for phosphorylation in the cardiomyocyte sarcolemma. Biochemical, cellular, and electrophysiological studies have suggested a number of possible roles for this protein, including ion channel modulator, taurine-release channel, Na(+)/Ca(2+) exchanger modulator, and Na-K-ATPase-associated subunit. We have generated a phospholemman-deficient mouse. The adult null mice exhibited increased cardiac mass, larger cardiomyocytes, and ejection fractions that were 9% higher by magnetic resonance imaging compared with wild-type animals. Notably, this occurred in the absence of hypertension. Total Na-K-ATPase activity was 50% lower in the phospholemman-deficient hearts. Expression (per unit of membrane protein) of total Na-K-ATPase was only slightly diminished, but expression of the minor alpha(2)-isoform, which has been specifically implicated in the control of contractility, was reduced by 60%. The absence of phospholemman thus results in a complex response, including a surprisingly large reduction in intrinsic Na-K-ATPase activity, changes in Na-K-ATPase isoform expression, increase in ejection fraction, and increase in cardiac mass. We hypothesize that a primary effect of phospholemman is to modulate the Na-K-ATPase and that its reduced activity initiates compensatory responses.

Automated quantitative analysis of angiogenesis in the rat aorta model using Image-Pro Plus 4.1.

This paper explains the automated image-processing steps for the quantification of microvascular growth formation in the rat thoracic aortic ring model, an ex vivo model using excised rings of rat aorta embedded in a collagen matrix which produce outgrowths of microvessels. This model of angiogenesis is useful to study the mechanism by which external agents inhibit or stimulate endothelial cell proliferation and tube formation. The manual quantification of blood vessel growth in this model is normally a time-consuming, error prone process. Former automated image analysis methods of the ring model are outdated and cannot be used with current software technology. A macro was created using Image-Pro Plus 4.1 software which was chosen for image analysis because it allows a high degree of control and replication of image-processing steps. The accuracy of this macro was determined by comparing automated counts to manual counts in 161 aortic rings. The square root of the manual count versus the square root of the automated count resulted in a root mean square value of 0.8305.