Somatotrophin increases thyroxine-5'-monodeiodinase activity in lactating mammary tissue of the cow
| Autor: | J. E. Keys, A. V. Capuco, J. J. Smith |
|---|---|
| Rok vydání: | 1989 |
| Předmět: |
medicine.medical_specialty
Endocrinology Diabetes and Metabolism Thyroxine deiodinase Mammary gland Kidney Iodide Peroxidase Endocrinology Mammary Glands Animal Pregnancy Lactation Internal medicine medicine Animals Bovine somatotropin Dairy cattle Chemistry Thyroid Body Weight Mammary tissue DNA Feeding Behavior Organ Size Thyroxine medicine.anatomical_structure Liver Growth Hormone Triiodothyronine Cattle Female Hormone |
| Zdroj: | The Journal of endocrinology. 121(2) |
| ISSN: | 0022-0795 |
| Popis: | The effect of administration of bovine somatotrophin (bST) on peripheral conversion of thyroxine (T4) to tri-iodothyronine (T3) was studied in non-pregnant lactating Holstein cows. Six cows were injected daily for 5 days with 40 mg recombinantly derived bST, while six control cows received excipient alone. Blood samples were collected hourly from 08.00 to 19.00 h on a single day the week before treatment and on days 4–5 of treatment. All other tissue samples were obtained at slaughter, 20–23 h after the last injection. Administration of bST increased milk production and caused a 9% increase in hepatic DNA. Consumption of feed did not differ between control and bST-treated cows. Treatment did not alter serum concentrations of T4 or T3, although concentrations of thyroid hormones in the serum increased from 08.00 to 19.00 h. Activity of thyroxine-5′-monodeiodinase (5′-D) in liver and kidney was similarly unaffected. However, activity of 5′-D in mammary tissue increased approximately twofold in response to bST administration. We suggest that an increase in mammary conversion of T4 to the more biologically potent thyroid hormone T3 plays a role in mediating the galactopoietic response of dairy cattle to bST. Journal of Endocrinology (1989) 121, 205–211 |
| Databáze: | OpenAIRE |
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