Am. J. Respir. Crit. Care Med., Vol 149, No. 1, Jan 1994, 227-231.
Effect of age on the contraction of pulmonary venous sphincters in rats
DE Schraufnagel, MM Kurtulus and TH Patel
Department of Medicine, University of Illinois, Chicago 60680-6998.
Pulmonary veins of rats have regular focal ringlike muscular constrictions
(sphincters) that deepen with stimuli, such as head injury, sufficient to
cause pulmonary edema. The depth of the individual constrictions on the
veins can be determined by casting the pulmonary circulation, fracturing
the cast veins at their narrowed points, and measuring the constriction
using a scanning electron microscope. A recent study in rats given a blow
to the head showed that the venous constriction was attenuated by
alpha-adrenergic antagonism, but interaction between the antagonist, the
animal body weight, and sex was found. Older, heavier male animals
constricted more. To clarify these factors and assess the change in
pulmonary venous sphincter contraction with age, 20 female Sprague-Dawley
rats aged 5, 10, 15, 20, and 30 wk had their lung vasculature cast with
methyl methacrylate. Of the 4 animals in each age group 3 were given a blow
to the head to constrict the veins while the plastic was solidifying. The
lungs were digested and the casts of the blood vessels were fractured,
exposing the constricted portions of the veins. The depths of these focal
constrictions were measured. In animals that received the head blow the
constrictions were 2.9 +/- 0.3% (5 wk), 4.1 +/- 0.3% (10 wk), 5.8 +/- 0.4%
(15 wk), 6.8 +/- 0.4% (20 wk), and 7.1 +/- 0.5% (30 wk) (p < 0.0001). To
separate age from weight, a multivariate regression that accounted for
venous contraction was carried out. Although head blow, age, and weight
were each individually important, the combined model showed age was
insignificant (p = 0.9) when weight (p = 0.02) was present.(ABSTRACT
TRUNCATED AT 250 WORDS)
