Dose-response relationships between porcine somatotropin, muscle composition, muscle fiber characteristics and pork quality.

Background : Peripheral arterial disease (PAD) is a disorder characterized by impaired blood flow to the legs and maladaptive changes in the skeletal muscle. It is generally accepted that the skeletal muscle characteristics in patients with PAD include decreased capillary density and an altered percentage of oxidative myofibers. The scientific literature is conflicting, and it is based on studies with small sample size and older methodologies of skeletal muscle analysis. In addition, women are under-represented or not included at all in these studies. Hypothesis : We hypothesized that there would be differences in skeletal muscle composition in PAD patients compared to healthy controls. We further hypothesized that there would be gender differences in skeletal muscle composition in PAD patients versus healthy controls. Methods : Thirty -one patients with PAD and 31 age-, gender-, and activity-matched healthy controls underwent gastrocnemius muscle biopsy. Capillary density analysis and muscle fiber type determination were performed using immunohistochemistry techniques. Capillary density was measured as endothelial cells per muscle fiber and endothelial cells per area (mm 2 ). Results : There was no significant difference in capillary density in patients with PAD versus healthy controls when measured as endothelial cells per fiber (mean = 1.45 ± 0.43 vs. 1.50 ± 0.35, NS) or area (mean = 1.20 ± 0.29 vs. 1.29 ± 0.33, NS). There was also no difference in muscle fiber type composition between the groups. In the PAD cohort, capillary density was significantly lower in the men versus the women (mean = 1.36 ± 0.35 vs. 1.59 ± 0.51, p=0.005). In our cohort of women, there was no difference in capillary density in patients with PAD versus healthy controls (N=12). In men, capillary density was significantly lower in the PAD group versus healthy controls (N=19, mean = 1.09 ± 0.20 vs. 1.28 ± 0.34, p=0.043). Conclusions : Our data fail to confirm the belief that patients with PAD have a decreased capillary density and an altered percentage of oxidative myofibers. However, we did find that gender has an important impact on these characteristics. Further study of skeletal muscle composition in PAD may help to better understand the functional relevance of the gender differences.

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Effect of sex and exogenous porcine somatotropin on longissimus muscle fiber characteristics of growing pigs.

Journal of Animal Science ◽

10.2527/1990.6841176x ◽

1990 ◽

Vol 68 (4) ◽

pp. 1176-1181 ◽

Cited By ~ 40

Author(s):

M. B. Solomon ◽

R. G. Campbell ◽

N. C. Steele

Keyword(s):

Muscle Fiber ◽

Fiber Type ◽

Live Weight ◽

Growing Pigs ◽

Fiber Types ◽

Longissimus Muscle ◽

Meat Tenderness ◽

Giant Fiber ◽

Porcine Somatotropin ◽

Dose Levels

Abstract Thirty-seven pigs with an initial live weight of 60 kg were used to investigate the effects of daily exogenous porcine somatotropin (pST) administration at two dose levels (0 and 100 µg·kg−1·d−1) for a 31-d period on muscle fiber characteristics and meat tenderness of boars, gilts and barrows. Excipient boars and gilts had more αW and fewer αR fibers than did those receiving pST. The percentage of muscle fiber type for barrows was not affected by pST treatment. The administration of pST resulted in an increase in muscle fiber size for all three fiber types in all three sexes, but these changes were of greater magnitude in barrows (31.8%) and gilts (27.8%) than in boars (9.3%). Somatotropin negated the intrinsic sex effect differences in fiber area of the pigs. There was no difference in tenderness among excipient boars, barrows and gilts; however, with the inclusion of pST, shear force decreased in boars and gilts and increased in barrows. A high proportion of the pST-treated pigs contained giant fibers in the longissimus muscle. Furthermore, a small proportion of the pST-treated pigs exhibited pale, soft, exudative muscle. Whether the giant fiber anomalies occurred through increased muscle activity or from fibers undergoing degenerative changes was not determined.

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