The effect of creatine monohydrate supplementation dose on tissue creatine uptake in rats

Abstract

The phosphocreatine energy system buffers alterations in metabolic demand and provides a reservoir of immediately available energy for cells. The capacity of this energy reservoir can be increased via oral creatine supplementation using creatine monohydrate (CM). We examined the relationship between CM supplementation and changes in total creatine compound (TCr) concentrations in various metabolically active tissues. 32 Sprague-Dawley rats (16 males, 16 females) were given ad libitum access to AIN-93G pelleted diet and water containing 0 g/L, 2.5 g/L, 5 g/L, or 10 g/L creatine monohydrate and 1% sucrose for 8 weeks. CM supplementation had no effect on the weight or food/water consumption of rats. CM supplementation at all doses significantly increased TCr concentrations in brain (BR) and extensor digitorum longus (EDL) muscle while a CM dose of 5 g/L was sufficient to increase TCr concentrations in soleus (SOL) and red gastrocnemius (RGAS). Females experienced increases in white gastrocnemius (WGAS) TCr concentrations in response to 5 g/L CM, but not 2.5 g/L or 10 g/L CM, while the WGAS in males was not responsive to any dose. Female cardiac muscle (HRT) was responsive to both 5 g/L and 10 g/L CM supplementation but no effect was observed in males. Both sex- and tissue-dependent responses to CM supplementation should be investigated further as such knowledge is required as there is an expanding body of research into the use of CM supplementation to treat various diseases or insults within metabolically active tissues.