INACTIVITY OF ACID-EXTRACTED GROWTH HORMONE INJECTED IN AQUEOUS SUSPENSION

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Abstract
The somatotropic activity of alkali- and acid-extracted growth hormone stored at various pH''s was tested. The U.S.P. Growth Hormone Reference Standard, an alkali-extracted preparation, was found to lose most its activity when stored at pH 3. Maximum stability was found at pH 11. No significant loss in activity was found between pH 5 and pH 11. Acid-extracted growth hormone showed the same activity at pH 3 or pH 11, but full activity was only found when the material was injected as a clear solution. Aqueous suspensions of acid-extracted growth hormone were found to be inactive. This effect was also evident after intravenous assay. It is concluded that alkali-extracted growth hormone such as the U.S.P. Growth Hormone Reference Standard should never be exposed to pH''s below 5 or above 11, while acid-extracted growth hormone, although not affected adversely by pH''s as low as 3, should only be injected as a clear solution.

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