MCA V mean and the arterial lactate-to-pyruvate ratio correlate during rhythmic handgrip

• Published in: Journal of applied physiology (1985) 2006-11, Vol.101 (5), p.1406-1411
• Main Authors: Rasmussen, Peter, Plomgaard, Peter, Krogh-Madsen, Rikke, Kim, Yu-Sok, van Lieshout, Johannes J., Secher, Niels H., Quistorff, Bjørn
• Format: Article
• Language: English
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00423.2006

Regulation of cerebral blood flow during physiological activation including exercise remains unknown but may be related to the arterial lactate-to-pyruvate (L/P) ratio. We evaluated whether an exercise-induced increase in middle cerebral artery mean velocity (MCA V mean ) relates to the arterial L/P ratio at two plasma lactate levels. MCA V mean was determined by ultrasound Doppler sonography at rest, during 10 min of rhythmic handgrip exercise at ∼65% of maximal voluntary contraction force, and during 20 min of recovery in seven healthy male volunteers during control and a ∼15 mmol/l hyperglycemic clamp. Cerebral arteriovenous differences for metabolites were obtained by brachial artery and retrograde jugular venous catheterization. Control resting arterial lactate was 0.78 ± 0.09 mmol/l (mean ± SE) and pyruvate 55.7 ± 12.0 μmol/l (L/P ratio 16.4 ± 1.0) with a corresponding MCA V mean of 46.7 ± 4.5 cm/s. During rhythmic handgrip the increase in MCA V mean to 51.2 ± 4.6 cm/s was related to the increased L/P ratio (23.8 ± 2.5; r 2 = 0.79; P < 0.01). Hyperglycemia increased arterial lactate and pyruvate to 1.9 ± 0.2 mmol/l and 115 ± 4 μmol/l, respectively, but it did not significantly influence the L/P ratio or MCA V mean at rest or during exercise. Conversely, MCA V mean did not correlate significantly, neither to the arterial lactate nor to the pyruvate concentrations. These results support that the arterial plasma L/P ratio modulates cerebral blood flow during cerebral activation independently from the plasma glucose concentration.