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Effect of Pituitary Gland Activity on Longissimus Muscle Postmortem Glycolysis in the Pig

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

Abstract

Twenty-eight crossbred gilts averaging 61 kg body weight were used to determine if the rate of postmortem glycolysis in longissimus muscle of the pig could be altered by varying the level of anterior pituitary gland activity. Ten gilts were hypophysectomized (H) and 18 were sham hypophysectomized (SH) and assigned to the following groups: H + saline (H-s); H + pituitary powder (H-pp); SH + AIMAX + saline (SH-As); SH + saline (SH-s) and SH + pituitary powder (SH-pp). Animals were injected intramuscularly with saline or pituitary powder suspended in saline, and the SH-As pigs were fed AIMAX (a hypothalamic blocking agent) daily from 4 weeks after surgery until necropsy at 7 weeks after surgery. We assumed that the level of pituitary activity might follow the order: SH-pp > SH-s SH-As H-pp > H-s. Samples were removed from the left longissimus muscle during exsanguination (time 0) and at 30-, 60-, 120- and 180-min postmortem.

Blood levels of glucose and lactate indicate that these metabolites or the general metabolic rate decreased with decreasing pituitary activity. Longissimus muscle pH, temperature, lactate, glucose-6-phosphate, creatine phosphate, adenosine triphosphate and cyclic adenosine monophosphate at 0- and 180-min postmortem and the patterns of depletion or accumulation of metabolites over the 3-hr postmortem period suggest that the rate of postmortem glycolysis in longissimus muscle of the pig can be altered by changing the level of pituitary activity in the live animal. Possible enzyme systems that may be affected are phosphorylase, phosphofructokinase, pyruvate kinase, myosin ATPase, adenyl cyclase and phosphodiesterase. The results of this study suggest that pigs that display the condition of pale-soft exudative musculature (PSE) may hypersecrete one or more pituitary gland hormones before exsanguination and indicate that we will be able to define which pituitary hormone or hormones cause conditions in the live animal that result in PSE pork postmortem.

¹ Present address: Richard B. Russell Agr. Res. Center, Athens, Georgia 30604.

² The authors thank Dr. Dennis N. Marple for performing radioimmunoassay of the pituitary powder for ACTH and GH. Appreciation is extended to Mr. Kenneth Bender, Mr. Robert Johnson and Mr. James Lilly for their diligent care of the experimental animals and to Mr. Harry Young and Mr. James Faltynski for their assistance in the recovery of necessary organs from the experimental animals.