B. Singh et al., ULTRACYTOCHEMICAL STUDY OF MULTIPLE-DOSE EFFECT OF MONASTRAL BLUE UPTAKE BY EQUINE PULMONARY INTRAVASCULAR MACROPHAGES (PIMS), Journal of submicroscopic cytology and pathology, 26(2), 1994, pp. 235-243
The pulmonary intravascular macrophages (PIMs) of the ponies possess a
ll the characteristics of a fully differentiated resident macrophage,
which forms adhesive plaques with the capillary-endothelial cells. In
addition, it has a unique surface coat which does not conform to the c
oncept of a carbohydrate rich membrane bound glycocalyx generally asso
ciated with macrophages. We studied the responses of these cells espec
ially in the context of its globular surface coat to multiple doses of
monastral blue (MB), a copper tracer substance. The ponies were treat
ed with three doses of MB intravenously: 0.2 ml/kg body weight on day
0, 0.1 ml/kg at 48 h and a 0.05 ml/kg at 96 h after the first dose. Th
e examination of lung tissue at the ultrastructural level revealed int
ernalization of MB following complexing with the surface coat globules
along the entire cell surface. The cell surface was extensively ruffl
ed in the form of several lamellipods. The MB-globule complex was inte
rnalized mostly at the coated pits whereas concurrent internalization
of nascent globules of the coat took place at the ruffled surface. In
the former, the internalized material was seen in small, medium and la
rge phagolysosomes which stained intensely for acid phosphatase, where
as in latter case enzyme activity was entirely absent in all the nasce
nt globules carrying endosomes. Simultaneously there was hypertrophy o
f the Golgi complex, which showed intense staining for acid phosphatas
e. Relative to the Golgi response, acid phosphatase-positive tubular l
ysosomes in close association with extensive bundles of microtubules w
ere conspicuous, thus adding to the battery of cell organelles of secr
etory pathway. These results indicate that PIMs have an enormous poten
tial for the uptake of exogenous MB pigment, a capacity which is perha
ps dependent upon the presence of globular surface coat.