Abstract
Measurements of the total lung weights and the individual weights of the lung lobes of male F344 rats ranging in age from about 30 days to 140 days or more were made in order to determine how lung growth and the growths of the individual lung lobes relate to bodyweight over the course of maturation of this species. Additionally, in this study we also (1) compared how each lung lobe grows relative to total lung growth, (2) evaluated the ratios of lung dry weight to wet weight and (3) obtained information on the weights of the trachea and extra-hilar main-stem bronchi as the F344 rat matures. The wet weights W LT of the trachea-lung preparations and the pooled lobe weights W PL as functions of rat bodyweight W B could be readily described by the following logarithmic expressions: W LT = 0·596 ln W B - 1·923, r = 0·95; W PL = 0·464 ln W B - 1·566, r = 0·96. Expressed as percentages of the pooled lobe weights, the individual lobes remained at constant values as the animals grew with the exception of the right caudal lobe which decreased between bodyweights of 72 and 96 g; absolute wet weight measurements of the individual lobes indicated that the right cranial, right middle and right intermediate lobes actually decreased in weight between bodyweights of 300 and 385 g. The dry weights of the lobes consistently represented approximately 22% of the wet weights regardless of animal age or bodyweight, and on average the airways represented about 20% of the weights of the intact airway-lung preparations over the course of animal maturation.