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Journal of the Anatomical Society of India

Morphometric Study of Rat Prostate in Normal and Under Stressed Condition

Author(s): Mukerjee B, Rajan T

Vol. 53, No. 2 (2004-07 - 2004-12)

Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry.


Male albino rats were studied under two types of stresses; (i) maternal deprivation from day 5 to 20 day postnatal and (ii) foot-shock from day 21 to day 70. Later, period up to day 98, was post-shock recovery period. Results show that body weight is retarded due to maternal deprivation and foot-shock. In the post-stress period, increase in body weight was enhanced but could not equal the body weight of normal control rats. Between day 42 and day 98, weight of the prostate increased 13.09 times in normal rats but stressed rats prostate increased only 9.06 times of the weight recorded on day 42. Increase in total volume of prostate in growing rats was progressive up to day 98 which was mainly due proliferation of the mucosa and stroma of the prostate gland. As a result of chronic stress, the volume of the prostatic mucosa was markedly affected.

Key words: Rat, stress, body weight, prostate, morphometry.


In the active reproductive period of males, prostate gland plays an important role; for this reason the prostate has been studied in various ways in number of animals and man Jen and Nixon (1995) and Kellokumpu-Lehtinen et al (1979)and many mammalian animals, for example, Shrew Mathur and Goyal (1974), Armadillo Weaker (1978), Weaker (1980), Squirrel Siwela and Tam (1984), Guineapig, Pig Nicaise et al, (1991), Marsupial Macdonald et al (1980), Deer Champman et al (1980), Camel Ali et al (1978) and Monkey Wakui et al (1992). However, among the host animals, Rat Moore et al (1930), Dorothy Price (1937), Flickinger (1972, 1977), Huttunen et al, (1981), Steins et al (1981), Martikainen and Swominen (1983), Aumuller et al (1985, 1989, 1998), Gottreich et al (1996); Hayward et al (1996a, 1996b), Ruis et al and Mice Cunha (1972, 1973), Sinha and Bentley (1984), Singh et al (1999) have been used most extensively. In the present study too, albino rats were utilized to estimate the effect of stress from early postnatal life to sexually mature active reproductive period of life in male Wistar rats. This study puts forward the report in two stages of rats life, (1) pre-weaning period (day 5 to day 20) and (2) postweaning period (day 21 to day 70). This study also includes the effect of withdrawal of chronic stress on the body weight and the weight and volume of prostate gland and its constituents in male Wistar rats.

Material and Methods:

Pregnant Wistar rats housed in cages measuring 40 x 15 x 16 cm were maintained in our environment controlled viverium. The ambient conditions were, 22 ± 12 degree temperature and relative humidity ranged between 58 and 73%. The light : dark cycle was regulated at 12:12 hr (lights on 600 hr and off 1800 hr). The rats were fed on diet as per recommendations of the National Institute of Nutrition (NIN), Hyderabad. The diet consisted of wheat flour 22.5%, roasted Bengal gram flour 60%, groundnut flour 10%, skimmed milk powder 5%, casein 4% (80% protein), refined oil 4%, salt mixture 4.8%, vitamin 0.5%. Scale of diet: 15 to 20 g/day. Clean drinking water (pH 2.0 to 2.5) was provided ad libitum. Near full term, pregnant rats were monitored every 8 hourly. The day of delivery was designated as day one of pup's age. Before day 5, groups were formed. Each group consisted of five male rat pups.

Maternal deprivation stress regimen:

From day 5 maternal deprivations was executed as per the schedule given below:

Day Duration/ L:D Cycle Total stress/ 24 hr.
5 to 7 1: 1 hr 2 hr
8 to 14 2: 2 hr 4 hr
5 to 20 3 :3 hr 6 hr

From day 21 weaning was started and the young pups were segregated from mother rat, and housed in separate cages. All the groups were fed solely on solid diet and water recommended by NIN.

Foot shock stress regimen:

From day 28 to day 70 the young rats were subjected to electrical foot shock in an avoidance box, Takaki & Co. Japan (Fig.1a & b) having stainless steel bars on the floor, spaced 1 cm apart. Scrambled foot-shocks were presented from an automatic shock generator. Intensity of foot shock was 0.5 mA for 2 sec. at 1 min interval; such 30 foot shocks were inflicted once in each light : dark cycle. From day 35, keeping the same time schedule, the intensity of foot shock was increased to 1 mA. After the foot shock treatment on each day the rats were returned to their home cages and food and water was restored. At 12 hourly interval, regular foot-shock treatment continued till day 70; thereafter till day 98 the stressed group of rats were maintained free from stress treatment .

Table I. Body weight of male Wistar rats grown under maternal deprivation stress in the pre-weaning period and under foot-shock stress in the post-weaning period up to day 70 and in stress free period up to day 98

Age (days) Body Weight ( g)
Control Times Increase/week Stressed Increase/week Times
0 5.22 ± 0.33     5.18 ± 0.21    
7 11.18± 0.73 2.14 5.96 9.51± 0.63 * 4.41 1.86
14 20.66± 0.39   9.48 10.63± 1.48 *** 4.12  
21 25.89± 1.31 4.95 5.23 21.11± 1.63** 7.48 4.13
28 35.88± 5.24   9.99 27.24± 1.91* 6.16  
35 52.90± 1.68   17.02 37.70± 2.25*** 10.46  
42 80.18± 1.43   27.28 46.90± 2.19*** 9.2  
49 105.86±1.41   25.68 72.94± 4.17*** 26.04  
56 140.58 ±2.16   34.72 97.46±5.56*** 24.52  
63 180.66±3.43   40.08 114.78±2.22*** 17.32  
70 203.80±4.40 39.04 23.14 128.66±4.12*** 13.88 25.22
77 220.44±3.82   16.64 135.82±3.62*** 7.16  
84 250.33±7.90   29.89 149.40±3.78*** 13.58  
91 265.92±3.80   15.59 185.82±3.64*** 36.42  
98 280.52±8.30 53.72 14.6 201.44±4.15*** 15.62 39.49

0.05; **p < 0.01; ***p < 0.001

Table II. Weight of prostate of rats under normal and under chronic stress

Age (days) Weight of Prostate ( mg )
Control Times Increase/Week Stressed Times Increase/Week
42 15.48 ±2.59     14.28 ± 0.28 **    
49 25.71 ± 4.45   10.23 23.64 ± 4.89 *   9.36
56 37.74 ± 8.59   12.03 27.42 ± 6.86*   3.78
63 54.55 ± 7.88   16.81 29.57 ± 9.67**   2.15
70 78.74 ± 4.87 5.08 24.19 35.68 ±3.66*** 2.49 6.11
77 111.94±10.63   33.20 49.24 ± 8.75***   13.56
84 158.2 4 ± 8.89   46.30 74.22 ±7.87***   24.98
91 186.56 ±12.42   28.32 97.32 ±14.23***   23.10
98 202.74 ±13.20 13.09 16.18 129.42 ±17.97*** 3.62 32.10

* p < 0.05, ** p< 0.01, *** p < 0.001

Fig. 1a

Missing Image

Animal sacrifice and tissue processing:

From day 42 till day 98, one control and one experimental group of rats were weighed and sacrificed by deep anesthesia. Prostate gland with prostatic urethra was dissected out, weighed and processed for paraffin embedding, sectioning , and staining by haematoxyline and eosin. The volume estimation was recorded stereologically on days 42, 56, 70, 84 and 98.

For the purpose of stereology an eye-piece reticule (American Opticals, Cat.No.41723-086) was used. The reticule has 10 mm square subdivided into 1.0 mm squares.

Height of the prostatic epithelium was measured by an ocular micrometer scale. Absolute volume of the tissue components of the prostate gland was morphometrically calculated as volume /cu mm (Weibel and Elias, 1967).

Vi = Pi /Pt
Vi = Volume fraction.
Pi = number of intercepting points of the reticule on the tissue component.
Pt = total number of intercepting points in the reticule.

Data Analysis:

The data obtained from the control and stressed groups were computed for mean and standard error (SEM). Student's ‘t' test was performed. The probability level of p = 0.05 was taken as the limit of significance.


The body weight of normal healthy Wister rat pups increased 2.14 times of the birth weight in first week postnatal. Maternal deprivation executed from day 5 postnatal showed its effect within 2 days, thus on day 7 the body weight was1.86 times. On day 21 while the body weight of normal rat became 4.95 times, the maternally deprived rats gained 4.13 times of birth weight. In the post weaning period the effect of foot- shock stress was evident as found on day 70, normal rats weighed 39.04 and stressed rats weighed 25.22 times of birth weight. This continued and by day 98 (14 wks), normal rats weighed 53.73 times and stressed group of rats weighed 39.49 times of birth weight. It is notable that generally the weekly increase in the body weight of stressed rats were lesser than that of the normal healthy rats but the rats which were freed from chronic stress on day 70, after 2 weeks of stress free living, gained more body weight per wk than that of the normal healthy rats [Table I].

The weight of prostate gland of normal Wistar rats progressively increased, it became 5.08 times heavier between day 42 and day 70 but increased slowly there after gaining 2.57 times between day 70 and day 98. Weight of the prostate gland of rats grown under chronic foot-shock increased only 2.49 times between day 42 and day 70 and 3.62 times between day 70 and day 98, indicating that after 2 wks of withdrawal of stress, the prostate of stress freed rats increased more at a faster rate than the normal rats. It was also observed that in normal rat, prostate weighs 0.02% on day 42, 0.04% on day 70 and 0.07% on day 98 of the body weight (Table II).

The epithelium of prostatic mucosa was characterized by columnar cells resting on the basement membrane. At places of epithelial folds, they appeared aggregated and shorter. Only the places where they were resting erect on the basement membrane, their height was measured. The epithelial height of normal rat prostate ranged between 11.23+0.89 mm on day 42 and 19.53 + 0.97 mm on day 98. In stressed rat it was significantly low. The nuclear diameter of the prostatic epithelial cells varied within small range of about one- third to one-fourth times of the height of the epithelial cells. It was significantly affected by stress (Fig.2).

From 6th week, the total volume of prostate gland of rat increased regularly, thus the absolute volume of the prostatic components like epithelium and stroma increased (Table III).

Fig. 2. Height of epithelial cells and nuclear diameter (µ m) of rat prostate

Missing Image

Table III. Absolute volume (mm3) of components of prostate gland of rat

Age(days) Epithelium Stroma Lumen
Control Stressed Control Stressed Control Stressed
42 27.26±9.83 11.12±2.55*** 22.36±4.53 23.10±1.68 15.35±2.87 11.69±4.34
56 37.19±6.94 21.17±7.95*** 26.82±6.25 21.23±9.88* 28.22±4.84 32.23±3.74
70 58.79±16.42 23.92±6.88*** 33.15±12.68 23.68±5.37** 52.60±7.85 49.22±8.87
84 63.21±23.58 46.89±24.65*** 39.75±5.18 35.72±9.23* 60.85±6.48 49.40±13.15**
98 77.53±24.54 56.43±28.25*** 46.11±8.64 39.35±7.42* 69.54±22.83 50.42±15.22**

*p < 0.05; **p < 0.01; ***p < 0.001


For any species, early postnatal stress causes different degree of distressful situation which may lead to fatal end. Therefore, in designing a stress paradigm, caution should be exercised to protect the life of the experimental animal, otherwise the sample size may drop below the requirement of the statistical analysis. The present study fulfilled the necessity, therefore, regular but intermittent maternal deprivation was started from day 5 postnatal, because it is known that interruption of mother-infant contact is a stressful experience that has adverse biochemical, physiological and behavioral consequences for the offspring. In rat pups ornithine decarboxylase (odc), a sensitive index of growth and differentiation decrease in brain and heart after just one hour of maternal deprivation, Kuhn et al (1978). Same report reiterated that in adult rats stress significantly retards body weight in 7 days period. In the present study, body weight of young rats markedly retarded within two days of intermittent maternal deprivation stress. Earlier reports on the effect of different kinds of stresses have all shown retardation of body weight Armario et al (1984) Ortiz et al (1985), Gamello et al (1986), Mukerjee (1987) Alario et al (1987). During the period when active growth process of the and its constituent parts (organs) are taking place, stress progressively affect body in many ways, presumably all organs. In the present study, it is evident that while the body weight of the healthy male rats were progressively increasing the body weight of rats suffering chronic intermittent stress have always lagged behind but after withdrawal of foot-shock on day 70, the body weight gain expedited and after two weeks of stress-free living, the weekly increase of body weight was more than double of the body weight of the normal rats.

As for the prostate gland, its weight has been reported from day 42, although the body weight was recorded from first week postnatal, this is because although Dorothy Price (1930) reported on rat and Cunha (1972) reported on mice that prostate begins to develop in the intrauterine life. The present study does not substantiate the same. The embryology books describe that prostate develops as proliferation of multiple outgrowths from prostatic urethra, Moore & Persaud (1998) and Sadler (2004). The number of the outgrowths are variable and their complete development period is uncertain that is why in this study weight and volume of the prostate gland has been recorded from day 42 which for albino rats is around puberty by which time prostate gland is presumably fully formed and the results of this study show the effect of stress on the prostate. The other problem with prostate gland is that in some animals like deer, Chapman and Chapman (1980) and squirrel, Siwella and Tom (1984), the growth of prostate is linked with seasonal changes which alter the size of the prostate gland. Therefore, morphometric study of the prostate gland can best be undertaken with certain due considerations.


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