STUDIES ON THE CHEMISTRY AND PHARMACOLOGY OF THE MELANOPHORE HORMONE OF THE PITUITARY GLAND

¹ From the Department of Pharmacology, University of Chicago, Chicago, Illinois

The melanophore hormone may be completely potentiated at pH 11 after three minutes' boiling or at pH 9 after two hours. Owing to an equilibrium condition established between the unpotentiated and the potentiated substance at a pH lower than 9, potentiation does not undergo completion even after prolonged boiling.

The reaction of potentiation is of the first order; the increasing rate of potentiation is approximately doubled at every ten-degree increase of temperature.

Destruction of the melanophore hormone occurs slowly in N/1 NaOH at 25°C., and increases rapidly with the rise of temperature or alkalinity.

The unpotentiated and the potentiated melanophore substances are qualitatively and quantitatively different in their pharmacological effects as is indicated by the intensity and the duration of response of the melanophores.

The intensty of the melanophore response may be used as an index for measuring the activity of a melanophore preparation. This is based upon a logarithmic relation between dosage and the extent of expansion of the melanophores.

When the logarithms of the time of the total response are plotted against the logarithms of dosage, a straight line is obtained for both the unpotentiated and the potentiated melanophore substances. However, the slope and the intercept of the straight line for the unpotentiated substance are different from those for the potentiated. This linear relationship between the logarithm of dosage and that of the duration of response is utilized for the quantitative assay of the melanophore activity of the unpotentiated and the potentiated preparations.