Diverse and distinct auto-, para-, and endocrine stimuli arriving at the surface of endothelium, smooth muscle cells, cardiomyocytes and fibroblasts within the myocardium, engage cell type-specific receptors, which lead to transmission of signals across the cell plasma membrane and result in the production and activation of second messengers. The most common mechanism by which these second messengers function is via direct or indirect activation of specific protein kinases. The current challenge for scientists is to identify the specific substrates (for example, metabolic enzymes, Ca2+-regulating proteins, transcription and mitotic factors) for the many protein kinases, to elucidate the biological significance of the cell type-specific expression heterogeneity of signalling proteins (eg membrane receptors, isoenzymes of protein kinase C, G-proteins) and to unravel the cross-talk interaction between the signalling systems (eg phospholipase C with adenylate cyclase and phospholipase C with phospholipase D).This text provides an up-to-date source of information for all scientists and clinicians interested in the mechanisms by which external signals are transmitted to the interior and regulation of a variety of physiological, pathological and pharmacological responses.
