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Postmortem Glycolysis in Longissimus Muscle of the Hypophysectomized Pig

U. S. Department of Agriculture, Beltsville, Maryland 20705

Abstract

Fourteen crossbred gilts 190 days of age and 66 kg body weight were used to study the effect of hypophysectomy (hypox) on the rate of postmortem glycolysis and levels of glycolytic intermediates in longissimus muscle of the pig. Seven pigs were hypoxed (H) and seven were sham hypoxed (SH). The pigs were weighed and bled at the time of surgery, and at 3-week intervals until necropsy at 12 weeks after surgery. Samples were removed from the left longissimus muscle during exsanguination and at 15, 30, 60, 120 and 180 min. postmortem.

Growth was severely retarded in the H pigs compared to the SH pigs. Within 3 weeks after surgery blood glucose, lactate and cholesterol were significantly lower (P < .01) in H pigs than in SH pigs. After exsanguination muscle pH decreased more slowly (P < .05) and carcass temperature decreased more rapidly (P < .01) in the H pigs than in SH pigs. Initial muscle glycogen was similar in both groups, but by 3 hr. postmortem glycogen was significantly (P < .05) higher in H pig muscle than in SH pig muscle. Initial levels of muscle lactate and glucose and the rate of lactate and glucose accumulation were significantly (P < .01) lower in H pigs than SH pigs. Initial levels of hexose monophosphates were significantly (P < .05) lower in H muscle than in SH muscle, and this difference persisted throughout the postmortem period. In general, F-D-P, 3-PGA and 2-PGA were similar in both groups, and remained stable throughout the postmortem sampling period. Time 0 levels of pyruvate were significantly (P < .05) lower in muscle of H pigs than in muscle of SH pigs, but the rate of decline of pyruvate was significantly (P < .01) slower in H pig muscle than in SH pig muscle. It was suggested that hypox might have depressed the rate of postmortem glycolysis at the phosphorylase, phosphofructokinase and pyruvic kinase sites. These results indicate that removal of anterior pituitary hormones from the living animal by hypox suppressed the rate of postmortem glycolysis in the longissimus muscle of the pig.

¹ Animal Physiology and Genetics Institute, Agricultural Research Center, Agricultural Research Service.

² National Program Staff, Livestock and Veterinary Sciences, Agricultural Research Service.

³ The authors thank Mrs. B. J. Davis and Miss S. F. Harris for their valuable technical assistance.