Hostname: page-component-8448b6f56d-xtgtn Total loading time: 0 Render date: 2024-04-23T14:49:37.455Z Has data issue: false hasContentIssue false
  • English
  • Français

Effects of prolonged administration of a β-agonist drug, ritodrine, on cardiovascular, metabolic and endocrine responses to adrenaline in growing ram lambs

Published online by Cambridge University Press:  27 March 2009

J. M. Bassett
J. M. Bassett
Affiliation:
The Growth and Development Unit, University of Oxford, University Field Laboratory, Wytham, Oxford 0X2 8QJ, UK
Get access Rights & Permissions [Opens in a new window]

Summary

Five Suffolk crossbred ram lambs were administered ritodrine, a β2-agonist drug, by continuous intravenous infusion at 0·5 μg/kg per min for 9 days to determine effects of prolonged β-agonist infusion on metabolism and on the responsiveness of the animals to short-term infusions of adrenaline. Consistent with other investigations, this study showed that initially the drug caused rapid increases in heart rate and plasma concentrations of free fatty acids (FFA), lactate and insulin, but decreased plasma growth hormone. There was no effect on plasma glucose or pancreatic glucagon concentrations. After 24 h of ritodrine infusion, these effects were attenuated as tachyphylaxis to the drug developed. On days 2–9 of the infusion, heart rate remained significantly higher than preinfusion values, but plasma glucose concentration was significantly lower than before infusion. Despite the rapid disappearance of these ‘side-effects’ of the drug and the apparent normality of most metabolic parameters, short-term infusion of adrenaline (50 ng/kg per min for 60 min then 500 ng/kg per min for a further 60 min) after 9 days of ritodrine infusion showed that the responses of lactate, FFA and heart rate to adrenaline were significantly attenuated in comparison with the responses determined before β-agonist infusion. This result, together with similar earlier observations on fetal lambs, implies that selective attenuation of β-receptor mediated cardiovascular, metabolic and endocrine responses to the endogenous catecholamines could play an important role in determining how β-agonist drugs act to modify carcass development.

Type
Animals
Information
The Journal of Agricultural Science , Volume 120 , Issue 1 , February 1993 , pp. 121 - 128
Copyright
Copyright © Cambridge University Press 1993

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Bassett, J. M. (1970). Metabolic effects of catecholamines in sheep. Australian Journal of Biological Sciences 23, 903–914.CrossRefGoogle ScholarPubMed
Bassett, J. M., Burks, A. H., Levine, D. H., Pinches, R. A. & Visser, G. H. A. (1985). Maternal and fetal metabolic effects of prolonged ritodrine infusion. Obstetrics and Gynecology 66, 755–761.Google ScholarPubMed
Bassett, J. M., Hanson, C. & Weeding, C. M. (1989). Metabolic and cardiovascular changes during prolonged ritodrine infusion in fetal lambs. Obstetrics and Gynecology 73, 117–122.Google ScholarPubMed
Bassett, J. M., Weeding, C. M. & Hanson, C. (1990). Desensitization of β-receptor mediated responses to epinephrine in fetal lambs by prolonged ritodrine administration. Pediatric Research 28, 388–393.CrossRefGoogle ScholarPubMed
Bassett, J. M., Bowman, A. S., Hanson, C., Rodway, R. G. & Speed, P. R. (1993). Attenuation of metabolic and endocrine responses to a β-agonist, salbutamol, in growing lambs. Lack of effect on responses to ‘dipping’, a stressful husbandry procedure. Animal Production 56, 107–114.Google Scholar
Blum, J. W. & Flueckiger, N. (1988). Early metabolic and endocrine effects of perorally administered β-adrenoceptor agonists in calves. European Journal of Pharmacology 151, 177–187.CrossRefGoogle ScholarPubMed
Brockway, J. M., MacRae, J. C. & Williams, P. E. V. (1987). Side effects of clenbuterol as a repartitioning agent. Veterinary Record 120, 381–383.CrossRefGoogle ScholarPubMed
Eisemann, J. H., Huntington, G. B. & Ferrell, C. L. (1988). Effects of dietary clenbuterol on metabolism of the hindquarters in steers. Journal of Animal Science 66, 342–353.CrossRefGoogle ScholarPubMed
Harden, T. K. (1983). Agonist-induced desensitization of the β-adrenergic receptor-linked adenylate cyclase. Pharmacological Reviews 35, 5–32.Google ScholarPubMed
Harris, V., Faloona, G. R. & Unger, R. H. (1979). Glucagon. In Methods of Hormone Radioimmunoassay (Eds Jaffe, B. M. & Behrman, H. R.), pp. 643–656. New York: Academic Press.Google Scholar
Hausdorff, W. P., Caron, M. G. & Lefkowitz, R. J. (1990). Turning off the signal: desensitization of β-adrenergic receptor function. FASEB Journal 4, 2881–2889.CrossRefGoogle ScholarPubMed
Klein, S., Peters, E. J., Holland, O. B. & Wolfe, R. R. (1989). Effect of short- and long-term β-adrenergic blockade on lipolysis during fasting in humans. American Journal of Physiology 257, E65–E73.Google Scholar
Malbon, C. C., Hadcock, J. R., Rapiejko, J., Ros, M., Wang, Hsien-Yu & Watkins, D. C. (1990). Regulation of transmembrane signalling elements: transcriptional, post-transcriptional and post-translational controls. Biochemical Society Symposia 56, 155–164.Google ScholarPubMed
Mersmann, H. J. (1989 a). Influence of infused β-adrenergic agonists on porcine blood metabolites and catecholamines. Journal of Animal Science 67, 2633–2645.CrossRefGoogle ScholarPubMed
Mersmann, H. J. (1989 b). Acute changes in blood flow in pigs infused with β-adrenergic agonists. Journal of Animal Science 67, 2913–2920.CrossRefGoogle ScholarPubMed
Prokocimer, P. G., Maze, M., Vickery, R. G. & Hoffman, B. B. (1988). Mechanism for desensitization of β-adrenergic receptor-stimulated lipolysis in adipocytes from rats harboring pheochromocytoma. Endocrinology 123, 528–533.CrossRefGoogle ScholarPubMed
Rikhardsson, G., Johnson, K. A. & Johnson, D. E. (1991). Effects of cimaterol on energetics and carcass characteristics of Suffolk ewe lambs. Journal of Animal Science 69, 396–404.CrossRefGoogle ScholarPubMed
Scheidegger, K., Robbins, D. C. & Danforth, E. (1984). Effects of chronic beta receptor stimulation on glucose metabolism. Diabetes 33, 1144–1149.CrossRefGoogle ScholarPubMed
Wallace, A. L. C. & Bassett, J. M. (1970). Plasma growth hormone concentrations in sheep measured by radioimmunoassay. Journal of Endocrinology 47, 21–36.CrossRefGoogle ScholarPubMed
Williams, P. E. V. (1987). The use of β-agonists as a means of altering body composition in livestock species. Nutrition Abstracts and Reviews (Series B) 57, 454–463.Google Scholar