INTERMEDIATE LOBE PITUITARY HORMONE
Authors: Landgrebe F. W. , Waring H. 
Published: December 2014

1. The optimum source for the manufacture of melanophore hormone (B hormone) is the posterior lobe of the pituitary, provided that the pressor and oxytocic autacoids can be removed without recourse to caustic soda treatment.

2. Previous methods of assaying melanophore activity are criticised, and the advantages of hypophysectomised Xenopus lævis as a test animal are emphasised.

3. A provisional unit of melanophore activity is proposed.

4. A new and rapid method is described for the preparation of B extracts which are substantially free from pressor substance (less than 1 unit of pressor activity in 4000 melanophore units) and oxytocin (less than 1 unit in 40,000 melanophore units). The final product in powder form keeps indefinitely and may be standardised on a weight basis with fair accuracy.

5. The preparation of B‐containing pituitary extracts is examined in detail. The oxytocic, pressor, and melanophore principles from posterior‐lobe extract are adsorbed by active charcoal. In 1 hour 25 p. c. of the melanophore activity can be eluted from the charcoal with pure water‐free liquid phenol. In this time little or no vasopressin and oxytocin are eluted.

6. The rôle of caustic soda, hitherto widely used to remove pressor and oxytocic properties from B‐containing extracts, is explored. Caustic soda treatment of general extracts modifies the melanophoric properties in at least two ways: (a) the melanophore‐expanding potency is increased; (b) there is an increased duration of the response when sub‐maximal doses are injected.

7. Differences in the response curves of hypophysectomisedXenopus to caustic treated and untreated whole pituitary extracts are not primarily due to the destruction of the pressor activity. In crude posterior‐lobe extracts there is a substance other than pressor autacoid or B‐precursor which, after treatment with caustic, modifies the melanophore response evoked by B hormone in the two ways noted. This substance is adsorbed on to charcoal from untreated extracts but is not eluted in 1 hour by phenol. After treatment of the general extract with caustic soda this substance, presumably modified by caustic, is adsorbed by charcoal, and is now eluted, together with melanophore‐dispersing hormone, by phenol. This substance may be oxytocin.

8. Since the alterations brought about by caustic treatment (para‐graph 6 above) in the melanophoric properties of an extract depend on the effect of the alkali on some pituitary constituent other than B, quantitative estimations of the B content of pituitary substance or of body fluids (e. g. blood) cannot furnish reliable data if caustic soda is used in the preparation of the extracts injected into the test animal.

9. Evidence is presented to substantiate the view that melanophore‐dispersing hormone is not passed by the kidney but is destroyed in the tissues. We were unable to detect the presence of B hormone in the urine of normal human beings.

10. Recent findings on the physiological role or pharmacodynamic effect of B hormone, other than the co‐ordination of chromatic response, are briefly reviewed.