of Florida, Gainesville, FL 32611-
Effect of Bovine Interferon on Acute Changes in Body Temperature and Serum Progesterone Concentration in Heifers
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G. R. NEWTON,1,3 s. MARTINOD,2 P. J. HANSEN,1,4 THATCHER,1 B. SIEGENTHALER,2 GERBER,2 and M•..J. VOIROL2 Dairy SCIence Department University of Florida Galnesvlle 32611 and elBA-GEIGY, S. A centre de Recherches Agrlcoles CH-1566 St. Aubin, Switzerland
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decreased with repeated daily exposure to interferon-all. The increase in rectal temperatures was associated temporally with a decrease in serum progesterone. Effects of interferon-all on body temperature and circulating progesterone could possibly limit its effectiveness in enhancing fertility. (Key words: interferon-a, hyperthennia, progesterone)
ABSTRACT
Bovine interferon-all has extensive sequence and functional homology with the antiluteolytic protein, bovine trophoblast protein-I. Because of the possible use of interferon-alIas a drug that supplements embryonic secretion of bovine trophoblast protein-I, interferon-all was tested for other biological actions that might affect its usefulness as a fertilityenhancing treatment. Experiments were performed to evaluate whether interferonall causes hyperthennia and an acute depression in circulating concentrations of progesterone. In four experiments, intramuscular administration of interferonall (range 1.25 to 20 mg) caused hyperthermia; average peak body temperatures of 40 to 4O.4·C occurred 2.5 to 6 h ,after injection. Temperatures returned to baseline 12 to 16 h later. The rise in rectal temperature could be reduced, but not totally alleviated, with concomitant administration of an inhibitor of prostaglandin synthesis. The maximal hyperthermic response was similar when interferon-aIl was delivered via osmotic minipumps or through a series of intramuscular injecThe hyperthermic response tions.
INTRODUCTION
Received December 14, 1989. ~ted
August I, 1990. 1University of Florida. 2cmA-GmGY S. A 3Current address: Coopemtive Agriculture Research Center, Prairie View A&M University, Prairie View, TX 77446-2866. 4aeprint requests: P. J. Hansen, IFAS 0701, University of Florida, Gainesville, FL 32611-1 ng/ml) or absence «1 ng/ml) of a corpus luteum (CL). Functional lifespan of the CL was dermed as the number of days from the previous estrus and the 1st d that the concentration of progesterone in serum was less than 1 ng/mI. Limit of detection of the assay was .05 ng/tube. Interassay and intraassay CV averaged less than 10%. StatlsUcal Analysis
Rectal temperatures (Experiments 1 to 4) and serum concentrations of IbIFN-a (Experiments 1, 2, and 4) were subjected to least squares analysis of variance (26). Orthogonal contrasts were used to determine differences between treatment groups. The effects of rbIFN-o; on concentrations of progesterone in serum in Experiment 2 were assessed by least squares analysis of variance with the zero-hour measure used as a covariate because heifers in this experiment did not have synchronized estrous cycles. The model, which examined effects on mean concentrations of progesterone after rbIFN-a administration, included effects due to treatment, heifer, period, and concentration of progesterone at 0 h. Treatment differences were evaluated by orthogonal contrast. In Experiments 3 and 4, treatment effects on estrous cycle lengths and luteal lifespan were determined by one-tailed Student's t test. RESULTS Dose-Response Relationship between Interferon, Hyperthermia, and Acute Changes In Progesterone
In Experiment 1, a single injection of either 5 or 20 mg of rbIFN-a caused rectal temperaJournal of Dairy Science Vol. 73,
No. 12. 1990
3442
NEWTON ET AL.
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T m e (h) Figure 1. Effect of a single i.m. administration of 0 (e), 1.25 (V), 2.5 ~, 5 (.6) 10 (A) or 20 (0) mg interferon-a on hyperthermia in Experiment 1 (top panel) and Experiment 2 (bottom panel). For both experiments, effects of treatment (P
