Studies On The Activity Detection And Release Of Sustained Release Recombined Bovine Growth Hormone In Animals

Somatotropin is one of polypeptide that synthesized and secreted by the eosinophil of anteriorpituitary. Somatotropin is capable of promoting the growth of animal, producing more milk andincreasing the transformation rate of feed and the muscle ratio of animal. Our experiment was mainlyfocused on the measurement of recombined bovine somatotropin(rbST) biological activity andmedication dynamics in rat.Firstly, experimental animal model of hypophysectomized rats through surgery was successfullyestablished. After surgery, 35 Wistar male rates survived from the total number 45, the successful rate ofsurgery was 77.8%. After 21 days of continuous observation of body weight, the weight gain of 15 ratswas less than 1g respectively, so they were determined as hypophysectomized completely. Thesuccessful rate of hypophysectomized rat was 33.3%To detect the promoting growth effect of recombined bovine somatotropin, the control group wasadministered with PBS subcutaneously at 120ul / rat/d, the three expe~'nent groups (experimentgroupⅠ,ⅡandⅢ) were administered with rbST solution subcutaneously at 50μg/rat/d, 100μg/rat/d and200μg/rat/d respectively and the injection lasted for 21days continuously The results showed that thethree experiment groups at different doses had the effect of promoting growth and the promoting growtheffect had positive relation with rbST doses. The feed and water intakes of the control group were theleast and that increased with higher doses of rbST for the experimental groups. After 2 hours of the lastinjection, the concentration of somatotropin in the blood had positive relations with the injection doses.The somatotropin was underdetection in the control group. The concentration of somatotropin fromexperimentⅠ,ⅡandⅢwere 3.68 ng/ml, 5.57 ng/ml and 6.12 ng/ml respectively. The result of thestudy showed that the rbST has the ability to promoting bovine growth.To test the sustained-release growth promoting effect of rbST oil suspension, eighteen malehypophysectomized rats were divided into five groups, four groups of which were treated with differentdoses of rbST oil suspension injection and one group was treated with PBS as a control. On the first dayof the experiment, the four experiment groups (experiment groupⅠ,Ⅱ,ⅢandⅣ) were administeredsubcutaneously 4.2% long acting rbST oil suspension at 0.84, 1.4, 2.8 and 4.2 mg/rat, respectively, and the control group was administered PBS subcutaneously at 120ul/rat. All the rats were weighed daily inthe morning for 32 days successively to observe their body weight gain. The body weight ofhypophysectomized rats injected with PBS was rather steady. The cumulative body weight gain of thecontrol rats was 5.87g after 32 days and the percentage of body weight gain was 6.9%. The percentage ofbody weight gain of experiment groupⅠ,Ⅱ,ⅢandⅣwas 18.66%, 18.97%, 20.61%,and 27.38%respectively after 32 days. The body weight gain of the testing rats was still existent at 31 st day aftertreatment with rbST oil suspension in vivo, which indicates that the oil suspension can releasesuccessively in vivo for about 31 days and it has the potential to be developed successfully as a new longactive rbST formulation.Subquently, To detect the activity of sustained release recombined bovine somatotropin, KM micewere administrated subcutaneously with rbST oil suspension injection at1.5mg/mouse, 3mg/mouse and6mg/mouse, to observe the effect of sustained release by weighting about 30 days.Cumulative bodyweight gain of three experiment groups was higher than the control group. The percentage of bodyweight gain of experiment groupⅠ,Ⅱ,ⅢandⅣwas 34.14%, 40.68%,42.52% and 44.5% respectively.So this method can show activity of somatotropin, but not analyse quantitatively, and not confirm therelease period of rbST oil suspension injection.To study the pharmacokinetics of sustained release of long acting rbST oil suspension andmicrospore preparation in rats administered with dose of 120 ul per rat, the method of radiativeimmunity (RIA) was performed to detect the amount of rbST in plasma. The results showed that theeffect of promoting growth about oil suspension and microspore preparation was better than the controlgroup, the lever of rbST about the experimental groups was higher than the control group through 30days release. Drawn from the above, the oil suspension and microspore preparation could releasesteadily for 30 days.