Publication: The hepatocytes of the brown trout (Salmo trutta f. fario):A quantitative study using design-based stereology
Authors
Rocha, E. ; Monteiro, R.A.F. ; Oliveira, M.H. ; Silva, M.W.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
A stereological study was performed on
brown trout hepatocytes aiming to disclose whether
there are basic gender differences when minimal levels
of sex hormones exist, and also to establish a platform
for both interspecific comparisons and physiological
correlations. We used the so-called "design-based
stereology" (with no shape, size or orientation
assumptions) and also some new related statistics. Twoyear-
old brown trout were collected in April, and the
livers were fixed by perfusion. From liver slicing to
microscopical field selection, systematic sampling was
used. Stereology was applied at light and electron
microscopy. Target parameters were the relative and total
hepatocyte number, the mean individual hepatocyte
volume and surface, and also both relative and total
volumes, and surfaces, either of organelles or of cell
compartments. Observed variability was usually high,
but the precision of estimates was proved to be globaily
adequate facing the true biological variation amongst
specimens. Females had more hepatocytes per liver
( 1 . 7 9 ~ 1 0v~s. 1 . 1 2~1 0~C) .o nsidering the individual
hepatocytes, whereas no gender differences were
detected in the cell volume, males had higher values of
nuclear volume (199 vs. 151 pm3) and surface (170 vs.
131 pm2), endoplasmic reticulum volume I 1300 vs. 824 pm3), and microvilli volume (82 vs. 54 pm ) and surface
(1445 vs. 975 pm2). However, when dealing with
quantities per liver, gender differences were found only
in the volumes of dense bodies (56 vs. 97 mm3) and of
residual cytoplasm (169 vs. 341 mm3) - both volumes
were higher in females. Functional implications of data are discussed, namely that females seem to have basic
structural traits for coping with the later demands of
breeding. Data also support that structural remodelling
of hepatocytes occurs after breeding, urging to pursue
seasonal studies (namely on lysosomes). We advanced
the hypothesis that genders differ in microvilli surface
just to maintain an optimal physiological surface-to-volume ratio. Interspecific similarities and differences
were disclosed. For example, the number of
hepatocytes/cm3 of parenchyma of brown trout was
much lower than those reported in rainbow trout, but in
both trouts femaies seem to have an higher cell number.
In addition, when comparing the size of hepatocytes of
brown trout with that from other fish and mammals it
was suggested that major interspecific differences exist.
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