Morphometric analysis of the effect of chloroquine on rat foetal lung maturation

Pregnant Sprague-Dawley rats were injected with chloroquine phosphate (40mg/kg b. wt 1.p) in the late canalicular (day 20) and early terminal-sac (day 21) and sacrificed in the late terminal sac (day 22 = term) stage of foetal lung development. The control animal received normal saline. Morphometric evaluation of the lungs by light microscopy revealed three important exposure-related lesions. They were: (a) reduction in the volume density of parenchyma and saccular space, (b) reduction in the volume of an average saccule and, (c) an increase in the number of saccules per unit volume (Numerical Density). The observations suggest that chloroquine retards foetal lung maturation by reducing the saccular expansion which takes place immediately preterm. However, the possible practical implications are unclear.