ONE OF THE FACTORS GOVERNING THE RELAXATION OF NON-STRIATED MUSCLE (INTESTINE) BY COMMERCIAL PITUITARY EXTRACTS

¹ From the Department of Pharmacology, Washington University, School of Medicine, St. Louis, Missouri

1. Pure pituitary substance (M. S.) produces an increase in the tonus of longitudinal segments of rabbits duodenum and ileum.

2. Pure pituitary substance in some cases causes a temporary loss of tonus preceding the increased tonus.

3. All commercial preparations tested (12 different brands from 9 manufacturers) caused marked relaxation of the duodenum and usually also a loss in tonus of the ileum when added to the bathing solution.

4. All commercial pituitary extracts tested, which did not contain the preservative chlorbutanol, produced increased tonus of the intestinal segments when their pH by the addition of N/10 NaOH was made equal to that of the solution bathing the tissue.

5. Commercial pituitary extracts containing chlorbutanol, usually caused increased tonus, following their addition to the solution, when the pH of the product was raised to that of the bath. In those cases in which they did not cause this change, we believe the preservative chlorbutanol was responsible for the relaxation.

6. All commercial pituitary extracts tested were highly acid in reaction. It required from 1.5 to 1.56 cc. of N/10 NaOH to neutralize 1 cc. of "surgical pituitrin" and 1 cc. of "infundin." In the samples of "obstetrical pituitrin" tested only 1.05 cc. of N/10 NaOH was necessary to neutralize each cubic centimeter of the drug.

7. The relaxation observed in excised strips of intestine after the addition of commercial pituitary preparations to the bath we believe to be due to the changes in pH of the bath and not to the pituitary content. Chlorbutanol used as a preservative may itself cause loss of tonus.

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