Relationship of MTT reduction to stimulants of muscle metabolism.

MTT, a positively charged tetrazolium salt, is widely used as an indicator of cell viability and metabolism and has potential for histochemical identification of tissue regions of hypermetabolism. In the present study, MTT was infused in the constant-flow perfused rat hindlimb to assess the effect of various agents and particularly vasoconstrictors that increase muscle metabolism. Reduction of MTT to the insoluble formazan in muscles assessed at the end of experiments was linear over a 30 min period and production rates were greater in red fibre types than white fibre types.

Acute and chronic effects of capsaicin in perfused rat muscle: the role of tachykinins and calcitonin gene-related peptide.

In perfused rat skeletal muscle (hindlimb), capsaicin either stimulates (submicromolar concentrations) or inhibits (micromolar concentrations) oxygen consumption (VO2). Both VO2 effects are associated with vasoconstriction, evident as an increase in perfusion pressure (PP), under constant flow. We have proposed that these effects are mediated by two vanilloid receptor subtypes: VN1 (stimulation of VO2) and VN2 (inhibition of VO2) (; ).

Vascular control of nutrient delivery by flow redistribution within muscle: implications for exercise and post-exercise muscle metabolism.

There is evidence for non-nutritive flow routes within, or associated with, skeletal muscle. Large capillary-like structures are possible candidates. The proportion of flow distributed between nutritive and non-nutritive routes appears to be tightly regulated and can control muscle metabolism and contraction by regulating delivery and product removal.

Hormonal control of thermogenesis in perfused muscle of Muscovy ducklings.

Endocrine stimulation of muscle nonshivering thermogenesis (NST) in ducklings was investigated in vitro using a perfused hindlimb preparation maintained at 25 degrees C. Effects of flow rate, norepinephrine (NE), epinephrine, and glucagon on perfused muscle oxygen consumption (MO2) and perfusion pressure were studied. Control ducklings (Cairina moschata, 5 wk old) reared at thermoneutrality (25 degrees C, TN) were compared with two age-matched groups exhibiting muscle NST in vivo: cold-acclimated ducklings (4 degrees C, 4 wk, CA) and glucagon-treated ducklings (103 nmol/kg twice-daily, intraperitoneally, GT).

Potential for non-shivering thermogenesis in perfused chicken (Gallus domesticus) muscle.

The humoral modulation of resting muscle heat production of chickens (Gallus domesticus) was investigated in vitro. The resting distal lower limb was perfused via the popliteal artery at 25 degrees C without erythrocytes at constant flow. The preparation was stable for at least 3 hr, showing a constant oxygen uptake (MO2) and perfusion pressure as well as adequately maintaining muscle energy charge and creatine phosphate: creatine ratio.