Effect of Exogenous Porcine Somatotropin on Growth in Rats

INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY
1560–8530/2004/06–6–1140–1142
http://www.ijab.org
Effect of Exogenous Porcine Somatotropin on Growth in Rats

XU CHUAN-LAI, YAO HUI-YUAN ANDYAO GUO
School of Food Science and Technology, Southern Yangtze University, WuXi , Jiangsu, 214036

ABSTRACT

The growth effect of PST liposome on rats was conducted in this experiment in a sustained-release formulation. Both PST and
PST liposome stimulated growth performance of rats and differences between treatment groups and control group was
obvious. PST liposome, however, demonstrated great sustained-release effect, which lasted more than seven days.

Key Words: Porcine somatotropin (PST); Liposome; Growth effect; Reverse evaporating; Sustained-release

INTRODUCTION
MATERIALS AND METHODS



Growth hormone (GH) or somatotropin (ST) is a

Porcine somatoptropin (provided by Lupeng Bio-
single polypeptide chain consisting of 191 amino acids
technological Center/Shenzhen PRC.); ZFA-1 Revolving
(around 22,000 Da), varying considerably between species.
evaporator (supported by shanghai glass instrument second
The growth promoting effect of GH was shown in rats as
factory); Utrasonic processor (intensity 400W, frequency 20
early as in the 1920s by Evans and co-workers. They
KHz) (Sonics & Materials Vibra Cell; UV755B
demonstrated that GH increases weight gain (Evans &
spectrophotometer (Shanghai fine science instrument
Simpson, 1920) and stimulates protein accretion concurrent
factory).
with a reduction in fat deposition (Li-feng Chen et al.,
Experiment animals. The number of S-D male and female
1997).The effect was not studied in farm animals until the
rat was same, (from FuDan Univerisity medicine school,
1950s. For many years, it was not possible to apply this
shanghai)
knowledge to practice due to limited supply of GH.
PST liposome preparation (Qi neng Ping, 1999;
However, with the development of recombinant DNA
Zongxiang, 2001). PST liposome was prepared with the
techniques this has now changed, and porcine GH has been
method of reverse evaporating Weighing some Lecithin,
approved since 1995 (Sejrsen et al., 1995; Yihui Zheng,
cholestrol and octadecane (Fluka ) according to the ratio of
1996) for commercial use in growing pigs in Australia.
molecule(7:2:1) and transferring them to a round flask;
Recombinant bovine GH (rbST) is widely used to stimulate
adding Ether (30mL) into it and making it completely
milk production in cows, but it is not used commercially for
resolved, then resolve PST in PBS solution
growth promotion. GH cannot be administered orally, but by
(25ml,0.01mol/L);
the solution was treated 5min in
injection. For cattle, sustainable release formulations for
ultrasonic waves (intensity 40%, at 1s intervals);
monthly administration are on the market.
decompress evaporation (38 ) into a gum or membrane

Liposome was small vesicle which was similar to
state then with 25 ml PBS (0.01 mol) wash down the
biofilm, it was first found by English scholar, Bangham and
membrane. Decompress evaporation until removing all
Standish, when they studied phospholipid. The partitioning
ether, 5 min centrifugation at 3000 rpm to get rid of
of drugs between cell membranes and aqueous solutions has
superfluous PST, then store the product with N2 filled .
been widely studied using liposomes, which are model
Growth effect of PST liposome on S-D rats (Zongxiang et
membranes with a lipid bilayer structure. Multilamellar
al., 2001). Rats were fed preliminarily for 10 days on
liposomes (MLVs) have been used in a sedimentation
document’ data. They were grouped randomly into 4 groups
method to study drug–membrane interactions and to
with 16 rats per row. Females and males were in half, and
determine the membrane partition coefficient for drugs
bred in different boxes (differences of primary bodyweight
(Wolverton et al., 1992).
less than 3 g in the same row). The control group injected
Liposome can be decomposed in bodies, no poison
physiological saline (1mL) in the abdominal cavity. Group1
and immunity. What’s more, as a kind of drug-carrier it can
was injected with pure PST daily, 1mL for each
reduce the toxicity of drug. In the last years researchers have
(1.2mg/mL); Group 2 was injected once every 7 days
attached great importance to liposome and rapid progress
(8.4mg/ml); Group 3 was treated every 14 days
have been taken .PST encapsulated with liposome could not
(16.8mg/mL). All rats were fed under invariable
only protect drug from digestive loss but promote
temperature and humidity, allowing the free intake. The
absorption with the character of sustained-release effects.
wood scraps were changed everyday. From day 2, the rats

were weighed at 8:00 AM every morning and injected drug
in the abdominal cavity according to experimental

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EFFECT OF PORCINE SOMATOTROPIN HORMONE ON GROWTH / Int. J. Agri. Biol., Vol. 6, No.6, 2004

requirements.
the early work by Larry established that PST worked in
RESULTS
pigs. He also demonstrated that administration of bovine

GH to lactating dairy cattle enhanced milk production and

Data were subjected to analyses of ANOVA and
productive efficiency (milk produced/unit of food
effects of PST treatment on body weights were shown in the
consumed) of milk production (Harrelll et al., 1996;
Tables I to III.
Etherton, 2000). Much has happened since the early studies

Administration of PST to female and male rats
of PST and bovine GH by Larry. Approximately one-third
both in pure PST and PST liposome had demonstrated that
of the dairy herds in the United States (about 3000 cows) is
PST increased weight gain. When the dosage was in a range
supplemented with recombinantly derived bovine GH in a
of 5-6 mg/kg (according to bodyweight), there were no
sustained-release formulation that is administered every 14
deaths. At this level, the use of PST can be regarded safe
d to lactating cows to improve milk production and
and positive. From Tables I to III (7 days later) the
efficiency of milk production. PST has impressive effects on
differences between the control and trial rows are
growth. The extent to which this occurs is illustrated by
remarkable (P<0.05), while differences between the
studies in which maximally effective doses of PST (?100
experimental groups aren’t distinct. Day 14, the weight
?g/kg of body weight per day) have been administered to
gains made by these treatments trial group1, group 2 relative
growing pigs (for 30 to 77 d). These studies have
to controls were obvious (P<0.05), while group 3 showed no
demonstrated that growth rate is increased approximately
significant difference relative to the control group (P>0.05).
10% to 20%, feed efficiency (feed consumed/body weight
PST liposome had indicated great sustained-release effect
gain) is improved 13% to33%, and protein deposition
and the period lasted more than seven days. The results were
(muscle growth) is increased by as much as 62%.
agreement with the research of Li Zhen’s (Lizhen GaoMing

Despite these findings, little is known about the
et al. (2003).
exact metabolic pathways of PST liposome that mediate the

effects on the adipose tissue lipogenisis. Further studies
DISCUSSION
need to be conducted to precisely define how long the

sustained-release effect can hold and maybe it can be taken

The range of biological effects PST are extraordinary
orally one day.
and have been discussed previously (Rehfeldt et al., 2001)
CONCLUSION
Table I. Seven days later, female and male rat’s daily gain

Item
Primary weight g
7th day g
7days gain g
Enhanced weight %
Female Male Female Male Female Male Female Male
Control group
137.67±1.09 167.33±3.62 151.77±2.14 201.17±3.44 14.10±1.65 33.84±1.08 12.36a±1.19 20.22c±1.02
Group 1
139.5±2.77 165±4.17 163.51±3.00 209.68±4.20 4.01±1.85 44.68±3.86 17.21b±1.53 27.08d±2.61
Group 2
140.5±5.87 164.83±2.18 164.93±7.31 208.49±3.09 24.43±2.26 43.66±3.10 17.39b±1.42 26.49d±2.10
Group 3
140.4±3.81 165±4.33 164.1±3.69 208.68±5.53 23.7±1.27 43.68±2.38 16.88b±5.61 26.47d±1.39
A and b represent remarkable differences (P<0.05)

Table II. Fourteen days later female and male rats’ daily gain

Item
Primary weight/g
14th day/g
14 days gain/g
Enhanced weight %
Female Male Female Male Female Male Female Male
Control group
137.67±1.09 167.33±3.62 176.5±1.98 266.5±4.35 38.83±1.59 99.17±1.96 28.21e±1.00 59.27g±1.62
Group 1
139.5±2.77 165±4.17 202.17±1.20 279±6.87 62.67±1.74 114±5.33 44.92f±2.03 69.09h±2.92
Group 2
140.5±5.87 164.83±2.18 204±6.93 277.67±4.03 63.5±2.62 112.84±2.28 45.20f±2.20 68.46h±1.09
Group 3
140.4±3.81 165±4.33 181.67±4.96 264.33±6.86 41.27±5.00 99.33±2.97 29.39e±4.90 60.20g±1.83

Table III. Twenty eight days later females and males daily gain

Item
Primary weight/g
28th day /g
28days gain/g
Enhanced weight%
Female Male Female Male Female Male Female
Male
Control group
137.67±1.09 167.33±3.62 218.83±5.02 337.57±5.44 81.16±5.82 170.24±3.13 59.24i0±4.50 101.74k±2.44
Group 1
139.5±2.77 165±4.17 236.83±1.89 345.5±8.41 97.33±3.04 180.5±4.63 69.77j±3.51 109.34l±0.93
Group 2
140.5±5.87 164.83±2.18 236.33±7.78 347.46±7.03 95.83±3.13 182.63±5.52 68.21j±2.51 110.80l±2.89
Group 3
140.4±3.81 165±4.33 223.33±3.86 332.67±9.47 82.93±2.48 167.67±6.84 59.07i±3.54 101.62k±3.58



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CHUAN-LAI et al. / Int. J. Agri. Biol., Vol. 6, No.6, 2004


Lizhen GaoMing, Yu RuiSong et al., 2003. Preliminary study on extended-

The results demonstrate that pure PST and PST
release of pGH/liposome and its body weight increase effect on
hypophysectomized rats. ACTA Agri. Shanghai, 19: 107–8
liposome have the activity of promoting growth on female
Qi neng Ping, 1999. Modern Pharmaceutics. Beijing Medical Scientific
and male rats. The treatment groups show remarkable
Technical Press, PRC
differences (P<0.05) relative to control group. PST liposome
Rehfeldt C., G. Kuhn J. Vanselow et al. 2001. Maternal treatment with
behaved itself with fine sustained-release effects that can
somatotropin during early gestation affects basic events of
myogenesis in pigs. Cell Tissue Res., 306: 429–440
last more than 7 days.
Sejrsen, K., N. Oksbjerg, M. Vetsergaard and M.T. Sorensen, 1995. Growth

hormone and related peptides as growth promoters. In: Proc. Sci.
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(Received 11 June 2004; Accepted 12 October 2004)

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