The trabecula culture system: a novel technique to study contractile parameters over a multiday time period

In the intact heart, various triggers induce alterations in gene expression that impact on contractile function. Because changes in gene expression reflect altered protein expression patterns after 12-48 h, we developed a system in which intact twitching cardiac trabeculae can be studied for multiday periods. Right ventricular trabeculae from pentobarbital sodium-anesthetized rabbits were mounted in a sterile, closed muscle chamber. Over the first 48 h, developed force (F-dev) did not significantly change: 102.3 and 98.9% of the initial F-dev was observed after 24 and 48 h, respectively (n = 8). Also, neither diastolic force, time from peak to 50% relaxation (RT50), nor protein synthesis measured by a [H-3]leucine incorporation assay changed significantly over time. Contractile response after >48 h to an increase in extracellular calcium concentration (1.8 to 2.5 mM; F-dev increased 43.5%, n = 2) or to 1 mu M isoproterenol (F-dev increased 138.6% and RT50 decreased 34.9%, n = 2) was similar to those observed in freshly dissected preparations. In conclusion, this system can investigate contractile function of multicellular preparations under well-defined physiological conditions after events that alter gene and consequent protein expression.