title: Heat acclimation-induced changes in heart glycogen/glucose metabolism in rats.
abstract: Based on the observation that heat acclimation is a slowly developing response, evoked by continuous exposure to moderate heat, we investigated the time-dependent acclimatory changes of heart glycogen metabolism. Cardiac levels of key carbohydrate-related enzymes and substrates were studied in the function of the duration of short-term (STHA; 6, 12, 24 and 48 h) and long-term heat acclimation (LTHA; 7, 14, 21 and 30 days) to high environmental temperature (35 ± 1°C). The changes in heart glycogen metabolism during STHA could be separated in two phases: up to 12 h exposure, where significant decrease of the heart glycogen (Glk), glucose-6-phosphate (G6P), hexokinase (HK) activity as well as increase of heart glucose was observed; and from 24 to 48 h exposure, manifested with elevation of Glk, Glu, glycogen phosphorylase a (GPa), phosphofructokinase (PFK) and HK activities. The metabolic changes in the period of LTHA could also be seen as separate phases: in a period of 7-14 days of heat exposure there was an increase of heart Glk, Glu, G6P, HK, as well as a decrease of GPa and PFK, while in the period of 21-28 days there was more intensive rebound of Glk and G6P, increase of GPa activity and non-significant changes of Glu, HK and PFK. The results obtained have showed that acclimation to moderate hyperthermic environment has caused significant changes in examined parameters which differ depending on duration to the exposure: intensive stress-induced glycogenolytic and glycolytic processes in the period of STHA and intensive energy sparing, manifested by Glk deposition in the period of LTHA.
authors: Department of Physiology and Biochemistry, Institute of Biology, Faculty of Natural Sciences and Mathematics, University St Cyrilus and Methodius, Gazi Baba bb, 1 000 Skopje, Republic of Macedonia. mirsadadervisevik@yahoo.com
authors: Mirsada
authors: M
authors: Dervisevik
authors: Suzana
authors: S
authors: Dinevska-Kjovkarovska
authors: Biljana
authors: B
authors: Miova
authors: Slavco
authors: S
authors: Mitev
authors: Marjan
authors: M
authors: Velkovski
authors: Damjan
authors: D
authors: Susleski
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D005947:Glucose / Q000378:metabolism*; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D024981:Glycogen Phosphorylase / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D006358:Hot Temperature; D008297:Male; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism*; D025221:Phosphofructokinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D019298:Glucose-6-Phosphate; D006003:Glycogen; D024981:Glycogen Phosphorylase; D025221:Phosphofructokinases; D006593:Hexokinase; D005947:Glucose