The lung of the marmoset (Callithrix jacchus): ultrastructure and morphometric data

Owing to its small size (body weight 300-400 g), its modest demands on anim al husbandry, and in particular its relatively long life-span (up to 12 yea rs) the common marmoset (cotton ear marmoset: Callithrix jacchus (Cj)) migh t be a useful animal model to study the adaptive capacity to different ener getic demands, adverse environmental influences such as air pollution, and aging of the lung. In order to describe the gas exchange apparatus of healt hy marmosets as a basis for further pulmonary research, the lungs of three young adult animals have been analysed both qualitatively and quantitativel y (by morphometry) at the light and electronmicroscopic level. Qualitativel y, there is a general similarity in the architecture and structure of lung parenchyma between marmosets and other mammals. Quantitatively, the alveola r surface area was found to be 7662 +/- 1647 cm(2). Capillary surface area and volume were 6000 +/- 1549 cm(2), and 1.01 +/- 0.34 ml, respectively. Th e harmonic mean thickness of the air-blood barrier was 0.517 +/- 0.117 mu m . These morphometric parameters allowed to estimate the diffusing capacity for oxygen at 0.0299 +/- 0.0134 ml O-2 (sec mmHg)(-1). In comparison with m ammals of similar body size (rats, guinea pigs) it appears that the marmose t has a higher gas exchanging capacity of the lung, which might reflect the 'athletic' activity of this small primate. An incidental finding worth men tioning is the individual variability of septal structures due to variation s in capillary blood volume and hematocrit. The distinction between such fu nctional variations and subtle pathologic alterations of lung tissue requir es a morphometric analysis at the electron-microscopic level. (C) 2000 Else vier Science B.V. All rights reserved.