VEGF-A splice variants and related receptor expression in human skeletal muscle following submaximal exercise

VEGF-A contributes to muscle tissue angiogenesis following aerobic exercise training. The temporal response of the VEGF-A isoforms and their target receptors has not been comprehensively profiled in human skeletal muscle. We combined submaximal exercise with and without reduced leg blood flow to establish whether ischemia-induced metabolic stress was an important physiological stimuli responsible for regulating the VEGF-A system in humans. Nine healthy men performed two 45-min bouts of one-leg knee-extension exercise, with and without blood flow restriction. Muscle biopsies were obtained at rest and 2 and 6 h after exercise. Expression (mRNA) of the VEGF-A splice variants and related receptors [VEGF receptor (VEGFR)-1, VEGFR-2, and neuropilin-1] was determined by using qPCR. VEGF-A(total) expression increased more robustly after exercise with reduced blood flow, and initially this principally reflected an increase in VEGF-A(165). Six hours after exercise, there was a relatively greater increase in VEGF-A(189), and this response was not influenced by blood flow conditions. VEGFR-1 mRNA expression increased 2 h after exercise, and neuropilin-1 expression was transiently reduced, while all three receptors increased by 6 h. There was no evidence for the expression of the inhibitory VEGF-A(165B) variant in human skeletal muscle. Our study, reflecting both VEGF-A ligand and receptors, implicates metabolic perturbation as a regulator of human muscle angiogenesis and demonstrates that VEGF-A splice variants are distinctly regulated. Our findings also indicate that all three receptor genes exhibit different pretranslational regulation, in response to exercise in humans.

Extracellular fluid volume and central circulation after long lasting exercise and dehydration in conscious dogs

Two aspects of the recovery period after endurance exercise were investigated: a) the fluid distribution between the intra- and extravascular parts of the extracellular fluid volume (ECFV) induced by exercise dehydration, b) the cardiovascular response pattern [blood pressure (BP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), and central venous pressure (CVP)] to the heat load which results from the preceding exercise. Seven conscious dogs performed endurance exercise in a cool environment (16 degrees C) on a horizontal treadmill till 4% of the body weight was lost. It was found that about 70% of the total fluid loss of the body came from intracellular water. During exercise sodium and chloride concentrations rose by 6 mMol and 7 mMol respectively (P less than 0.005) and remained elevated throughout the early recovery period indicating a fluid loss of about 100-200 ml out of the ECFV. Direct measurements of the ECFV as sulfate space confirmed these values. Since the plasma volume remained unchanged, this fluid loss was carried totally by the interstitial fluid volume. Immediately after exercise body temperature was elevated by 1.5 degrees C and returned towards control within 90 min. Cardiac output was above control level for 2 h after the end of exercise, at first due to an increased HR and thereafter to an elevated stroke volume (SV) (P less than 0.02). CVP and TPR were below control levels for at least 2 h (P less than 0.01). A linear correlation was found between CVP and TPR. A close correlation existed between the body temperature and the cardiovascular parameters. It can be concluded that even long after exercise the cardiovascular system has to serve thermoregulatory needs.