Cell kinetics of lamina propria fibroblasts in normal adult hamster bronchus.

Abstract

Forty-nine 12-week-old male Syrian golden hamsters (Mesocricetus auratus), weighting 108 to 128 g, were injected i.p. with [3H]-thymidine (3HTdR 2 microCi/g body wt). Animals were divided into 7 weight-matched groups and were killed at 1 hour (day zero) and 1, 2, 3, 4, 7, and 14 days after thymidine injection. Lungs were fixed by vascular perfusion of 4% formalin/1% glutaraldehyde in 0.2 M cacodylate buffer at pH 7.4, cut at 2 microns, dipped in Kodak NTB3 or NTB2 nuclear emulsion, exposed for 2 weeks, developed and stained. In each airway cross-section, total epithelial and fibroblast counts and labeled cell count were estimated. A cell was considered labeled when 3 or more silver grains appeared on its nucleus. The background grain count was less than 1 grain per nucleus. Mean epithelial and fibroblast cell density in a 100 microns segment were respectively 14.8 +/- 0.1 and 6.6 +/- 0.1 cells (the second number is one standard error of the mean). One hour after labeling, their respective labeling indices (L.I.) were 0.13 +/- 0.02 and 1.24 +/- 0.1. On day 1, their L.I. doubled and then returned to the initial value. One hour after labeling, epithelial and fibroblast mean grain counts did not differ significantly. They were respectively 20.6 + 1, and 15.8 +/- 2. Because grain count intensity is closely related to DNA synthetic time, it seems plausible that epithelial and fibroblast synthetic times do not differ much. Cell turnover and cell cycle times were estimated from grain count dilution curves.(ABSTRACT TRUNCATED AT 250 WORDS)