Regulation of Oxidative and Glycogenolytic ATP Synthesis in Exercising Rat Skeletal Muscle Studied by31P Magnetic Resonance Spectroscopy

Autor: Graham J. Kemp, Campbell H. Thompson, A. L. Sanderson, G. K. Radda
Rok vydání: 1996
Předmět:
Zdroj: NMR in Biomedicine. 9:261-270
ISSN: 1099-1492
0952-3480
DOI: 10.1002/(sici)1099-1492(199609)9:6<261::aid-nbm430>3.0.co;2-b
Popis: 31P magnetic resonance spectroscopy measurements of pH and the concentrations of orthophosphate and phosphocreatine were used to estimate rates of glycogenolytic and oxidative ATP synthesis in rat leg muscle during 6 min sciatic nerve stimulation at different rates (1-4 Hz). To study the regulation of glycogenolysis during exercise, the apparent 'glycogenolytic capacity' (L(MAX)) was calculated from glycogenolytic ATP synthesis rate and orthophosphate concentration as a measure of the Ca2+-dependent activation of glycogen phosphorylase. This was found to be proportional to the total ATP synthesis rate (F), and to decline with time; expressed relative to total ATP turnover rate as L(MAX)/F, its initial value was 2.9+/-0.6, declining with half-time 1.4+/-0.4 min. The apparent 'mitochondrial capacity' (Q(MAX)), calculated from oxidative ATP synthesis rate and [ADP], was independent of ATP turnover rate, but increased with half-time 0.8+/-0.1 min to 29+/-2 mmol kg(-1) min(-1): thus [ADP] was the predominant but not the only influence on oxidative ATP synthesis. Numerical simulation shows that time-dependent changes in L(MAX)/F exert a strong influence on pH and on the concentrations of phosphocreatine and ADP.
Databáze: OpenAIRE
Externí odkaz: