Measurement of biological activity of somatotropin in hypophysectomized rats
Abstract
AIM: To develop a method for measurement of biological activity of recombinant
DNA-derived somatotropin (rhGH).
METHODS: The effects of varying the route, frequency and period of administration
of GH, the sex of test animals on the biological responses, body weight gain
(BWG), and tibial epiphyseal width (TEW), of hypophysectomized (Hypox) rats were
compared, respectively. 4-d BWG, 6-d BWG, and 6-d TEW tests were carried out
simultaneously in the same group of Hypox rats to determine the biopotency of GH
preparations according to a parallel line bioassay (6-point assay). The final
result was chosen from the test which had smaller values for the index of
precision (lambda) and the average rate of fiducial limits (ARFL) than other
tests.
RESULTS: No significant differences in the responses between male and female
rats, between sc and im, once daily and twice daily injections of bGH were found.
But the BWG and TEW of Hypox rats injected with 0.045 and 0.135 IU.d-1 of bGH for
6 d were significantly greater than that for 4 d. Both 4-d BWG test and 6-d BWG
test in the range from 0.020 to 0.500 IU.d-1 had values for lambda = 0.0660 and
0.1747, and for r = 0.9000 and 0.9237, respectively. Three estimates of rhGH
preparation compared with the International Standard for somatotropin (IShGH),
4.6132, 3.9829, and 4.8023 IU/ampoule, were obtained separately from 4-d BWG
test, 6-d BWG test and 6-d TEW test. And the result from 6-d BWG test was
reported finally because it had smaller values for lambda and ARFL (0.0608 and
37.907%) than other two tests.
CONCLUSION: Both BWG test and TEW test can be carried out simultaneously in the
same group of Hypox rats. 6-d BWG test seemed to be more suitable for potency
determination of GH preparations than 4-d BWG test and 6-d TEW test.
Keywords:
DNA-derived somatotropin (rhGH).
METHODS: The effects of varying the route, frequency and period of administration
of GH, the sex of test animals on the biological responses, body weight gain
(BWG), and tibial epiphyseal width (TEW), of hypophysectomized (Hypox) rats were
compared, respectively. 4-d BWG, 6-d BWG, and 6-d TEW tests were carried out
simultaneously in the same group of Hypox rats to determine the biopotency of GH
preparations according to a parallel line bioassay (6-point assay). The final
result was chosen from the test which had smaller values for the index of
precision (lambda) and the average rate of fiducial limits (ARFL) than other
tests.
RESULTS: No significant differences in the responses between male and female
rats, between sc and im, once daily and twice daily injections of bGH were found.
But the BWG and TEW of Hypox rats injected with 0.045 and 0.135 IU.d-1 of bGH for
6 d were significantly greater than that for 4 d. Both 4-d BWG test and 6-d BWG
test in the range from 0.020 to 0.500 IU.d-1 had values for lambda = 0.0660 and
0.1747, and for r = 0.9000 and 0.9237, respectively. Three estimates of rhGH
preparation compared with the International Standard for somatotropin (IShGH),
4.6132, 3.9829, and 4.8023 IU/ampoule, were obtained separately from 4-d BWG
test, 6-d BWG test and 6-d TEW test. And the result from 6-d BWG test was
reported finally because it had smaller values for lambda and ARFL (0.0608 and
37.907%) than other two tests.
CONCLUSION: Both BWG test and TEW test can be carried out simultaneously in the
same group of Hypox rats. 6-d BWG test seemed to be more suitable for potency
determination of GH preparations than 4-d BWG test and 6-d TEW test.