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Auburn University Agricultural Experiment Station, Auburn, AL 36830
Abstract
The rates of utilization of thyroxine and triiodothyronine and the calcium binding ability of sarcoplasmic reticulum fragments were compared in halothane-sensitive and normal swine. Thyroxine clearance rates were determined by monitoring the disappearance of a dose of 1 3 1 I-thyroxine to 10 halothane-sensitive gilts and barrows (five each) with halothane-resistant littermate controls of the same sex. Triiodothyronine clearance rates were determined by the continuous infusion of 1 3 1 I-triiodothyronine to two halothane-positive and two halothane-resistant gilts. Sarcoplasmic reticulum fragments were isolated from muscle biopsies from eight halothane-sensitive and eight halothane-resistant swine and their ability to bind calcium was determined by monitoring the uptake of 4 5 Ca in the presence of ATP.
Halothane-sensitive swine were found to have a significantly lower thyroxine half-life, thyroxine fractional disappearance rate, plasma thyroxine concentration and calcium binding by sarcoplasmic reticulum fragments. Halothane-sensitive swine had a significantly greater thyroxine distribution space, thyroxine metabolic clearance rate and triiodothyronine metabolic clearance rate. No differences were noted in the secretion rates of thyroxine or triiodothyronine and plasma concentrations of triiodothyronine.
1 Research supported by the Agricultural Experiment Station, Auburn University; by ARS, USDA Cooperative Agreement No. 12-14-7001-370; and by Auburn University Research Grant-in-Aid No. 2275-01-5081. The assistance of Dr. J. W. McGuire during the statistical analysis of these data is gratefully acknowledged.
2 Department of Animal and Dairy Sciences.
3 Departments of Physiology and Pharmacology, and Animal Health Research.
4 Department of Zoology and Entomology.
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