Cg. Prosser et al., EFFECTS OF CLOSE-ARTERIAL (EXTERNAL PUDIC) INFUSION OF INSULIN-LIKE GROWTH FACTOR-II ON MILK-YIELD AND MAMMARY BLOOD-FLOW IN LACTATING GOATS, Journal of Endocrinology, 142(1), 1994, pp. 93-99
Five lactating goats were infused, via an external pudic arterial cath
eter, 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), rec
ombinant human IGF-II (133 nmol/h) or IGF-I and IGF-II combined. The i
nfusion 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 ch
anged only slightly by saline (2%), but increased to 9% (P<0.05) in re
sponse 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 increase
d 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 IG
F-II alone. Whereas plasma glucose increased by approximately 10% duri
ng infusion of IGF-I alone or with IGF-II, it was not altered by infus
ion of IGF-II only. The rapidity and unilateral nature of the milk-yie
ld response to IGF-I and IGF-II is consistent with their acting direct
ly on mammary tissue itself. Thus, the present results demonstrate sim
ilar local and systemic actions induced by intramammary infusion of IG
F-II and IGF-I, although the magnitude of the response to IGF-II tends
to be less than that to IGF-I.