Journal of Applied Physiology, Vol 41, Issue 1 7-14, Copyright © 1976 by American Physiological Society
Reduced surface tension in lungs of fetal rabbits injected with pilocarpine
A. J. Corbet, P. Flax and A. J. Rudolph
After opening the maternal abdomen under methoxyflurane anesthesia, fetal
rabbits 25.5-28.5 days gestation were given an intraperitoneal injection of
pilocarpine (150 mg/kg) or saline through the intact uterine wall. They
were delivered by hysterotomy and sacrificed without breathing 2.5 h later.
Newborn rabbits 29.5 days gestation received an injection of pilocarpine or
saline at birth and breathed 30-120 min. Other newborn rabbits 29.5 days
gestation were alternately sacrificed at birth or after breathing 30 min.
Static pressure-volume curves with air showed decreased recoil and improved
air retention on deflation in fetal rabbits 25.5-27.5 days injected with
pilocarpine. There was no change in the static pressure-volume curve of
lungs filled with saline. The data suggest that pilocarpine reduced surface
tension by producing secretion of surfactant into air spaces. No change in
lung recoil occurred with pilocarpine at 28.5 days, or with pilocarpine or
breathing at 29.5 days. This may mean that air spaces at 28.5-29.5 days
contained optimal surfactant, so further secretion of surfactant stimulated
by pilocarpine or breathing failed to reduce surface tension.
