Muscle remodeling in relation to blood supply: implications for seasonal changes in mitochondrial enzymes

Abstract

SUMMARY We investigated if seasonal changes in rainbow trout muscle energetics arise in response to seasonal changes in erythrocyte properties. We assessed if skeletal muscle mitochondrial enzymes changed (1) acutely in response to changes in erythrocyte abundance, or (2) seasonally when we altered the age profile of erythrocytes. Rainbow trout were treated with pheynylhydrazine,causing a 75% reduction in hematocrit within 4 days. After erythropoiesis had returned hematocrit to normal, treated and control fish were subjected to a seasonal cold acclimation regime to assess the impact of erythrocyte age on skeletal muscle remodeling. Anemia (i.e. phenylhydrazine treatment) did not alter the specific activities (U g-1 tissue) of mitochondrial enzymes in white or red muscle. Anemic pretreatment did not alter the normal pattern of cold-induced mitochondrial proliferation in skeletal muscle,suggesting erythrocyte age was not an important influence on seasonal remodeling of muscle. Anemia and cold acclimation both induced a 25–30%increase in relative ventricular mass. The increase in relative ventricular mass with phenylhydrazine treatment was accompanied by a 35% increase in DNA content (mg DNA per ventricle), suggesting an increase in number of cells. In contrast, the increase in ventricular mass with cold temperature acclimation occurred without a change in DNA content (mg DNA per ventricle), suggesting an increase in cell size. Despite the major increases in relative ventricular mass, neither anemia nor seasonal acclimation had a major influence on the specific activities of a suite of mitochondrial enzymes in heart. Collectively, these studies argue against a role for erythrocyte dynamics in seasonal adaptive remodeling of skeletal muscle energetics.

Phenylhydrazine-induced anemia causes nitric-oxide-mediated upregulation of the angiogenic pathway in Notothenia coriiceps

“…To demonstrate that loss of Hb can induce an increase in markers of NO concentration, red-blooded N. coriiceps were treated with PHZ for 10 days. In previous studies that have utilized PHZ to induce anemia in salmonids -one intraperitoneal injection with PHZ (10 or 12.5g g -1 ) was sufficient to decrease dramatically and rapidly the Hct (Smith et al, 1971;Gilmour and Perry, 1996;McClelland et al, 2005). By 1 day post injection (dpi), the Hct was significantly lower than that of control animals and continued to decrease for several days before starting to recover 8-10 dpi.…”

“…To test our hypothesis, we produced an icefish model by treating adults of the red-blooded notothenioid N. coriiceps for 10 days with phenylhydrazine HCl (PHZ). Phenylhydrazine is a hemolytic agent that lyses RBCs, leading to the degradation and clearance of Hb and drastically reducing the hematocrit (Hct) and Hb concentration (Smith et al, 1971;Gilmour and Perry, 1996;McClelland et al, 2005). We reasoned that treatment of a red-blooded notothenioid with PHZ would induce severe anemia that could provide insight into what happens when the primary breakdown pathway for NO is removed.…”

Mechanisms underlying parallel reductions in aerobic capacity in non-migratory threespine stickleback (Gasterosteus aculeatus) populations

“…We measured enzyme activities for cytochrome c oxidase (COX; EC 1.9.3.1, complex IV in the electron transport chain), citrate synthase (CS; EC 2.3.3.1, a citric acid cycle enzyme), creatine phosphokinase (CPK; EC 2.7.3.2, an enzyme that reversibly catalyzes the transfer of phosphate between ATP and creatine phosphate, a compound that stores energy and A. C. Dalziel, M. Ou and P. M. Schulte facilitates intracellular ATP transfer), pyruvate kinase (PK; EC 2.7.1.40, an enzyme in the glycolytic pathway) and lactate dehydrogenase (LDH; EC 1.1.1.27, an enzyme that catalyzes the inter-conversion of pyruvate and NADH to lactate and NAD+, which is crucial for replenishing NAD+, and maintaining high glycolytic flux during cellular hypoxia) on whole-cell extracts from the ventricle, pectoral adductor and pectoral abductor at 25°C (e.g. Moyes et al, 1997;McClelland et al, 2005). We optimized all assays to ensure that substrates were not limiting and modified protocols for measurement using a plate spectrophotometer (Spectramax 190 -1 GPDH in 50mmoll -1 Tris, pH7.4).…”

Genomic and Metabolic Preparation of Muscle in Sockeye SalmonOncorhynchus nerkafor Spawning Migration

“…The CS was measured according to previously published protocols (McClelland et al 2005). Briefly, the CS assay buffer contained 20 mM TRIS (pH 8.0), 0.1 mM DTNB, and 0.3 mM acetyl-CoA.…”

“…HOAD was measured according to previously published methods (McClelland et al 2005) and consisted of 50 mM imidazole (pH 7.4), 0.1 mM acetoacetyl-CoA, 0.15 mM NADH, and 0.1% Triton X-100 at 340 nm.…”