M. PALUS
Institute of Computer Science,
Academy of Sciences of the Czech Republic
Pod vodárenskou vezí 2,
182 07 Prague 8, Czech Republic
E-mail: mp@uivt.cas.cz
C. SCHOFL, A. VON ZUR MUHLEN, G. BRABANT, K. PRANK
Department of Clinical Endocrinology, Medical School Hannover
Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
Calcium (Ca{2+}) is an ubiquitous intracellular messenger which regulates cellular processes, such as secretion, contraction, and cell proliferation. A variety of cell types respond to hormonal stimuli with periodic oscillations of the intracellular free Ca{2+} concentration ([Ca{2+}]_i) which can be modulated in their frequency in a dose-dependent manner. The period of these well-studied oscillations varies normally between 30 sec and a couple of minutes. Here we study [Ca{2+}]_i oscillations in clonal beta cells (hamster insulin secreting cells, HIT) under pharmacological stimulation. Besides the well-known high-amplitude low frequency oscillations we try to analyze for the first time low-amplitude high frequency oscillations of [Ca{2+}]_i under pharmacological stimulation which have not been explored in experimental approaches to date. Using coarse-grained entropy rates computed from information-theoretic functionals we demonstrate differences in temporal complexity of the fast low-amplitude [Ca{2+}]_i dynamics corresponding to different phases of pharmacological stimulation which are additional to the well-known dose-dependent pattern of low-frequency high amplitude [Ca{2+}]_i dynamics.