CONTRIBUTIONS TO THE PHARMACOLOGY OF EXTRACTS OF THE POSTERIOR LOBE OF THE PITUITARY GLAND

¹ From the Departments of Physiology and Pharmacology, The Johns Hopkins University

The intravenous administration of pituitary liquid causes a paling of the skin and of the visible mucous membranes, which is more marked in unanesthetized animals than under ether anesthesia.

Apnea, with alternating periods of rapid shallow respiration, occurs as a constant phenomenon in the unanesthetized dog. Under ether, dogs show relatively little alteration in respiration.

The circulatory changes following the administration of pituitary extracts into the unanesthetized dog are briefly:

1. Rise of mean pressure, due chiefly to an increase in the diastolic pressure indicating increased peripheral resistance. The systolic level plays a subordinate rôle in these changes.

2. Decrease in pulse pressure.

3. Marked slowing of the cardiac rate.

4. Decrease in minute volume output of the heart. The output per beat may remain unaltered, or may show a lowering.

5. Cardiac dilatation as seen by the fluoroscope and roentgenograms.

These changes indicate intense peripheral constriction of arterioles and capillaries, a fact verified by direct observation of blood vessels of the dog's ear.

Slowing of the heart occurs after removal of vagal influence by the use of large doses of atropine sulphate, thus suggesting a direct action on the myocardium or a diminished coronary flow.

Oxygen consumption is markedly reduced after pituitary extract injected into the unanesthetized animal.

There is an increase in hemoglobin content of the blood for a brief period immediately after intravenous injection of pituitary liquid.

In the etherized animal there is also an increase in the mean pressure, a rise in diastolic pressure, diminished pulse pressure and cardiac dilatation but less marked than in the case of the unanesthetized dog.

In so far as tested by us, Abel's purified pituitary tartrate possesses physiological properties identical with those of the best commercial extracts.