Nitric oxide and the control of mammary blood flow
P. Lacasse, V.C. Farr, S.R. Davis, C.G. Prosser
Dairy Science Group, AgResearch, Ruakura Research Centre, Private
Bag 3123, Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1995,
55: 14-16
Mammary blood flow (MBF) is a major determinant of the rate of
substrate supply for milk synthesis, but the control mechanism(s) of MBF
has not been elucidated. Our objective was to test the hypothesis that
local production of the vasorelaxant nitric oxide (NO) can regulate MBF.
Thus the response in MBF to intra-arterial infusion of the NO donor
diethylamine NONOate (NONate), and the inhibitor of NO synthesis N@-
Nitro-arginine (NNA) was measured in four lactating Saanen goats. MBF
was measured using a transit time ultransonic flow probe implanted
around the external pudic artery of one gland and infusions were made
via a catheter inserted into the same artery. In two goats, a flow
probe was implanted on the pudic artery of the contralateral gland.
NONate was infused for 60 mins. at 1.67 and 16.7ug/min and induced an
increase (P<0.01) in MBF which averaged 190 and 243% of the preinfusion
MBF, respectively for the duration of the infusion. There was no
significant difference between the does. The effect was more
pronounced in the infused gland compared with the non-infused gland (201
vs 111% of the preinfusion MBF;P<0.05) suggesting a direct effect on
mammary vasculature. In contrast to NONate, NNA infused at 1 and
4mg/min of arginine the NO precursor, with NNA markedly reduced the
latter's ability to decrease MBF(P<0.05). Again the effect was more
pronounced in the infused compared with the non-infused gland (P<0.05).
Together, these results indicate that NO is a major vasorelaxant of the
mammary gland casculature and that this substance is produced within the
gland.
Keywords: NZSAPAB;
blood flow; nitric oxide; mammary
Download abstract in text format
Last Updated 25-01-1997
