Increase in milk secretion and mammary blood flow by intra-arterial infusion of insulin-like growth factor-I into the mammary gland of the goat.
The close-arterial infusion of free insulin-like growth factor-I (IGF-I; 1.1 nmol/min) for 6 h into the pudic artery supplying one mammary gland of lactating goats caused a 25 +/- 6% (mean +/- S.E.M., n = 6) increase in the rate of milk secretion of that gland. The increase in the rate of milk secretion in the adjacent noninfused gland (14 +/- 4%) was not significantly different from that observed during saline infusion (4 +/- 5%). Blood flow to the infused gland was increased from 378 +/- 26 ml/min 1 h before to 487 +/- 56 ml/min approximately 5 h after the start of the infusion of IGF-I, declining to 420 +/- 44 ml/min approximately 2 h after the end of the infusion. The total concentration of IGF-I (free and bound) in milk of the infused gland was significantly higher than that of the non-infused gland. The concentrations of IGF-I in carotid arterial plasma samples increased during IGF-I infusion from a mean value of 32 +/- 2 nmol/l before to a maximum of 49 +/- 3 nmol/l 5 h after the infusion commenced. Circulating concentrations of total IGF-I declined slowly after the infusion with an estimated half-life of 5 h. Infusion of saline alone did not alter mammary blood flow or the concentration of total IGF-I in milk or plasma. The results indicate that the infusion of free IGF-I into the mammary arterial supply enhances milk secretion and mammary blood flow in intact, conscious goats.(ABSTRACT TRUNCATED AT 250 WORDS)
AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge.
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Prosser
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Fleet
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Corps
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Froesch
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Heap
D000818:Animals; D005260:Female; D006041:Goats / Q000502:physiology*; D007261:Infusions, Intra-Arterial; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology; D007774:Lactation; D008321:Mammary Glands, Animal / Q000098:blood supply* / Q000187:drug effects; D008892:Milk / Q000378:metabolism*; D012039:Regional Blood Flow / Q000187:drug effects
D007334:Insulin-Like Growth Factor I