TISSUE ATPASE ACTIVITY IN SOMATOTROPIN-TREATED PIGS

Authors: Caperna, Thomas; Gavelek, Debra

Submitted to: Energy Metabolism of Farm Animals Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/19/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: Administration of porcine somatotropin (pST) is associated with altered nutrient partitioning such that protein deposition is enhanced at the expense of energetic efficiency. A substantial portion of total energy expenditure is associated with visceral metabolism and specifically, in maintenance of cellular ion gradients. These experiments were conducted to determine the influence of short-term treatment of pST on the specific activities of visceral tissue ATPases. The specific activity of Na-K-ATPase was determined in liver, heart, kidney and duodenum. Enhanced growth of visceral tissues was evident in pigs treated for 6 and 14 d with pST. Treatment with pST was associated with an overall 19% increase in Na-K-ATPase activity in the liver; Addition of pST to primary monolayer cultures of porcine hepatocytes also resulted in increased Na-K-ATPase activity. The activities of Na-K-ATPase and Mg-ATPase in heart, kidney and duodenum were similar for control and pST-treated pigs. Ca-ATPase activity was also determined in tissues from pigs treated for 14 d with pST. The activity of Ca-ATPases was approximately 23% lower, in kidney medulla of pST-treated pigs, while Ca-ATPases in other tissues was not influenced by pST-treatment. It is concluded that some of the observed increase in energy expenditure associated with pST-treatment may be attributed to increased hepatic Na+ and K+ flux, but it does not appear that pST is a general activator of Na-K-ATPase and may also inhibit Ca ATPase.

Technical Abstract: These experiments were conducted to determine the influence of porcine somatotropin (pST) administration on the specific activity of visceral tissue ATPases. The specific activity of Na-K-ATPase (ouabain-sensitive adenosine triphosphatase activity) was determined on fresh homogenates of liver, heart, kidney and duodenum. As observed for pigs chronically treated with pST, enhanced growth of visceral tissues was evident in pigs treated for 6 and 14 d with pST. Treatment with pST was associated with an overall 19% increase in Na-K-ATPase activity in the liver; specific activity of Mg-ATPase was not influenced by pST. Addition of pST to primary monolayer cultures of porcine hepatocytes also resulted in increased Na-K-ATPase activity. The activities of Na-K-ATPase and Mg-ATPase in heart, kidney and duodenum were similar for control and pST-treated pigs. High and low affinity Ca-ATPase activities were also determined in tissues from barrows treated for 14 d with pST. The specific activitities of high and low affinity Ca-ATPases were 20 and 26% lower, respectively, in kidney medulla of pST-treated pigs. Ca-ATPases in other tissues including kidney cortex, were not influenced by pST-treatment. These data indicate that some of the observed increase in energy expenditure associated with pST-treatment may be attributed to increased hepatic Na+ and K+ flux. It does not appear that pST is a general activator of Na-K-ATPase and may also inhibit the activity of other tissue ATPases.