The effect of the hyperbaric environment on heat shock protein 72 expression in vivo

Heat shock protein 72 (HSP72) is expressed in response to stress and has been demonstrated to follow a diurnal expression pattern within monocytes and is sensitive to changes in core temperature. Numerous studies have shown changes in HSP72 expression within cell lines exposed to hyperbaric conditions. No studies have investigated changes in HSP72 expression in vivo. Six males participated in the study and were exposed to hyperbaric air and hyperbaric oxygen a week apart. Monocyte HSP72 was analyzed by flow cytometry at 09:00, 13:00, 17:00, 21:00 with hyperbaric oxygen or hyperbaric air breathing commencing at 15:00 for 78 min at a pressure of 2.8 ATA. HSP72 under normoxia followed the established trend; however, following the hyperbaric air or oxygen exposure a reduction in detectable HSP72 was observed at 17:00 and 21:00. No changes in core temperature were observed between 13:00 and 21:00 for any condition. The data show that HSP72 expression is impaired following hyperbaric air (HA) exposure, when compared with control or hyperbaric oxygen (HO) exposure.

Contraction-mediated glycogenolysis in mouse skeletal muscle lacking creatine kinase: the role of phosphorylase b activation

Skeletal muscle that is deficient in creatine kinase (CK-/-) exhibits accelerated glycogenolysis during contraction. Understanding this phenomenon could provide insight into the control of glycogenolysis during contraction. Therefore, glycogen breakdown was investigated in isolated extensor digitorum longus CK-/- muscle. Muscles were stimulated to produce repeated tetani for 20 s in the presence of sodium cyanide to block mitochondrial respiration. Accumulation of lactate after stimulation was similar in wild-type (WT) and CK-/- muscles, whereas accumulation of glucose-6-phosphate was twofold higher in CK-/- muscles, indicating greater glycogenolysis in CK-/- muscles. Total phosphorylase activity was decreased by almost 30 % in CK-/- muscle (P < 0.001). Phosphorylase fractional activity (-/+ 3.3 mM AMP) was similar in both groups in the basal state (about 10 %), but increased to a smaller extent in CK-/- muscles after stimulation (39 +/- 4 % vs. 52 +/- 4 % in WT, P < 0.05). Inorganic phosphate, the substrate for phosphorylase, increased marginally in CK-/- muscles after stimulation (basal = 25.3 +/- 2.2 micromol (g dry muscle)-1; stimulated = 33.9 +/- 2.3 micromol (g dry muscle)-1), but substantially in WT muscles (basal = 11.4 +/- 0.7 micromol (g dry muscle)-1; stimulated = 54.2 +/- 4.5 micromol (g dry muscle)-1). Kinetic studies of phosphorylase b (dephosphorylated enzyme) from muscle extracts in vitro demonstrated higher relative activities in CK-/- muscles (60-135 %) in response to low AMP concentrations (up to 50 microM) in both the basal state and after stimulation (P < 0.05), whereas no differences in activity between CK-/- and WT muscles were observed at high AMP concentrations (> 100 microM). These data indicate that allosteric activation of phosphorylase b accounts for the accelerated glycogenolysis in CK-/- muscle during contraction.