| Summary: | Pulmonary oedema is a life threatening complication of pregnancy. This project investigates lung structure in pregnancy using the MF1 mouse lung as a model in pursuit of knowledge applicable to human obstetrics. As well as histological examination of lungs from groups of normal nonpregnant control mice and normal pregnant mice at term, fine structural changes associated with pregnancy are studied quantitatively, employing stereological methods. Pulmonary interstitial volume doubles in pregnancy, this change being localised to ground substance especially which shows early pulmonary oedema. Significant increases in volume of basal lamina, endothelium, squamous (type 1) pneumocyte and alveolar luminal projections from the latter cell are seen. The histological significance of these adaptations is discussed. Alveolar surface area in pregnancy is 50&'37 more than in controls, the increase being mainly type 1 pneumocyte. There is, however, no change in number of alveoli or thickness of the pulmonary diffusion barrier. Haematological and protein biochemical studies in MF1 mice show changes in accord with accepted human findings. A quantitative method for measuring the concentration of endogenous albumin in aldehyde fixed resin embedded tissue sections by stereological immunogold electron microscopy is described. Control strategies are described and discussed. Results indicate an overall reduction in endogenous albumin staining in pregnancy; plasma concentration falls 22&'37 in pregnancy compared with controls (biochemically, albumin falls 29&'37). Similar changes are seen in interstitium, again localised to the ground substance. Staining in endothelium is 10&'37 that of plasma; endothelial cytoplasma shows a lower concentration of albumin staining than vesicle but, in contrast, more stainable albumin molecules. The relationships between concentrations of staining and between quantities of stainable albumin molecules are consistent between pregnant and control groups. The effective barrier to passage of albumin from plasma to interstitium is the luminal surface of the endothelium. It is concluded that significant changes in amounts of albumin in pulmonary compartments are seen in pregnancy compared with nonpregnant controls. It is argued that these changes probably do not relate to altered endothelial permeability in pregnancy.
|
|---|
