Abstract :
The aim of this study was to estimate the number and volume distribution of islets of Langerhans in post-weaning
young Wistar rat pancreas and their variation with age. Four groups of six normal Wistar Kyoto rats, at 3, 6, 9 and
12 weeks of age, were used. The whole pancreas was weighed (
W
), fixed in buffered formaldehyde and embedded
in JB4 resin, and 1.5-
μ
m serial sections were obtained. A fraction of whole tissue was obtained in accordance with
the multistage fractionator principle and used to estimate total number of islets (
N
is
). Volume fraction (
V
f
) of islets
and volume-weighted mean volume (
Vv
) of islets were estimated using point-counting and point-sampled intercept
methods, respectively. The numbers of islets increased steadily with age (
P <
0.001), whereas the volumeweighted
mean volume of individual islets was not significantly different among all age groups of rats (
P
> 0.05).
There was a strong positive correlation between total islet number and islet mass (
r
= 0.96,
P
= 0.001), and between
volume fraction and islet mass (
r
= 0.969,
P
= 0.001). However, there was a weak positive correlation between volume
fraction and volume-weighted mean islet volume (
r
= 0.6,
P
= 0.002) in the age window investigated. These
findings indicate that there was an increase in the number and volume fraction of islets with age in post-weaning
young rats but that individual islet volume did not change significantly. It appears the mechanism of alteration in
islet morphology in the rat is mainly by the formation of new islets while keeping their individual volume distribution
unchanged
