Journal of Applied Physiology, Vol 68, Issue 5 1786-1792, Copyright © 1990 by American Physiological Society
Effect of feeding regimen on diurnal variation of breathing movements in late-gestation fetal sheep
J. Callea, I. C. McMillen and D. W. Walker
Department of Physiology, Monash University, Clayton, Victoria, Australia.
There is a diurnal variation in the mean incidence and amplitude of fetal
breathing movements (FBMs) in sheep after approximately 120 days gestation.
To determine whether this variation is caused by diurnal fluctuations in
plasma glucose or prostaglandin (PG) concentrations, we studied two groups
of pregnant sheep fed either once daily at 1100 h or every 2 h for 24 h.
Maternal and fetal blood samples were taken every 2 h from 0900 to 0900 h
the next day for assay of plasma glucose and PGE2 and PGF2 alpha
concentrations. FBMs were recorded throughout the 24 h. The mean fetal
plasma glucose concentrations of the once-daily and multifed groups were
not different, but there was a significant difference between the two
groups in the 24-h pattern of fetal glucose concentrations. In the
once-daily fed group, plasma glucose concentrations reached a peak 8 h
after maternal feeding and then declined, whereas in the multifed group,
fetal plasma glucose concentrations reached a plateau and were constant
from 1300 to 0900 h the next day. Fetal plasma PGE2 and PGF2 alpha
concentrations did not show a significant change with time of day in either
group. There was a significant diurnal variation in the incidence and
amplitude of FBMs in each of the two feeding groups, and the 24-h pattern
of FBMs did not differ significantly between groups. Therefore it would
appear that the diurnal variation of FBMs is not a consequence of the
maternal feeding regimen or diurnal changes in plasma glucose or PG
concentrations.
