Effects of close-arterial (external pudic) infusion of insulin-like growth factor-II on milk yield and mammary blood flow in lactating goats.
Five lactating goats were infused, via an external pudic arterial catheter, directly into the mammary gland with 0.9% (w/v) NaCl (20 ml/h), recombinant human insulin-like growth factor-I (IGF-I; 80 nmol/h), recombinant human IGF-II (133 nmol/h) or IGF-I and IGF-II combined. The infusion was for 6 h and milk yield was determined every 2 h. The ratio of milk yield in the infused relative to the non-infused gland was changed only slightly by saline (2%), but increased to 9% (P < 0.05) in response to IGF-I and 8% (P < 0.05) in response to IGF-II. When combined, both peptides increased this ratio by 6%. These effects were elicited within 2-4 h of the beginning of infusion. Mammary blood flow increased 50-80% (P < 0.05) during all IGF infusions, but only 28% during saline treatment. Plasma insulin decreased 50% (P < 0.01) during the infusion of IGF-I alone or in combination with IGF-II and 25% in response to IGF-II alone. Whereas plasma glucose increased by approximately 10% during infusion of IGF-I alone or with IGF-II, it was not altered by infusion of IGF-II only. The rapidity and unilateral nature of the milk-yield response to IGF-I and IGF-II is consistent with their acting directly on mammary tissue itself. Thus, the present results demonstrate similar local and systemic actions induced by intramammary infusion of IGF-II and IGF-I, although the magnitude of the response to IGF-II tends to be less than that to IGF-I.
Prosser
C G
CG
Dairying Research Corporation Ltd, Ruakura Agricultural Centre, Hamilton, New Zealand.
Davis
S R
SR
Farr
V C
VC
Moore
L G
LG
Gluckman
P D
PD
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D005260:Female; D006041:Goats / Q000378:metabolism*; D007261:Infusions, Intra-Arterial; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism / Q000494:pharmacology*; D007774:Lactation / Q000187:drug effects*; D008321:Mammary Glands, Animal / Q000098:blood supply* / Q000187:drug effects*; D008892:Milk / Q000187:drug effects; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects
D001786:Blood Glucose; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II