title: The seasonal peculiarities of force-frequency relationships in active ground squirrel Spermophilus undulatus ventricle.
abstract: The plasticity of calcium homeostasis is of crucial importance for the unique ability of the hibernators' heart to function under conditions of body temperature changing from 37 degrees C to near freezing point. However, the precise mechanism of calcium homeostasis regulation in these animals is largely unknown. Force-frequency relationship, as an indicator of participation of various sources of calcium (external and intracellular) in the activation of contraction, and post-rest potentiation as an index of the capacity of sarcoplasmic reticulum (intracellular calcium source) to store and release Ca(2+), were studied to analyse the role of different calcium-transporting systems in seasonal and temperature-induced changes in isometric twitch force of ground squirrel papillary muscles. The obtained results revealed significant functional differences during the annual cycle, which are indicative of an increased role of the sarcoplasmic reticulum in regulation of contractility in animals in transition to the hibernation period. Also, how myocardium during the hibernation period copes functionally with acute decreases in temperature was investigated.
authors.affiliation: Institute of Cell Biophysics, Russian Academy of Sciences, Institutskaya Street 3, 142290 Pushchino (Moscow region), Russia.
authors.forename: Olga V
authors.initials: OV
authors.lastname: Nakipova
authors.forename: Nadezhda M
authors.initials: NM
authors.lastname: Zakharova
authors.forename: Ludmila A
authors.initials: LA
authors.lastname: Andreeva
authors.forename: Nadezhda A
authors.initials: NA
authors.lastname: Chumaeva
authors.forename: Aleksey
authors.initials: A
authors.lastname: Averin
authors.forename: Leonid S
authors.initials: LS
authors.lastname: Kosarskii
authors.forename: Andrey I
authors.initials: AI
authors.lastname: Anufriev
authors.forename: Dirk von
authors.initials: Dv
authors.lastname: Lewinski
authors.forename: Jens
authors.initials: J
authors.lastname: Kockskamper
authors.forename: Burkert
authors.initials: B
authors.lastname: Pieske
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006605:Hibernation / Q000502:physiology*; D006706:Homeostasis; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction; D009543:Nifedipine / Q000494:pharmacology; D010210:Papillary Muscles / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D012589:Sciuridae; D012621:Seasons; D013696:Temperature; D016276:Ventricular Function