Chester A. Meyers

Activity of VIP, somatostatin and other peptides in the mouse vas deferens assay.

Non-opiate peptides such as vasoactive intestinal peptide (VIP) and somatostatin were tested for their effects on electrically induced contractions of the vas deferens. VIP(ED50 = 2.7 X 10(-8) M) and to a lesser extent somatostatin (ED50 = 5.2 X 10(-8) M) were found to be in the same general range of activity as enkephalin and the endorphins in this system. Human pancreatic polypeptide (HPP) exerted a biphasic effect, inhibiting the contractions at high concentrations but enhancing them at lower concentrations. A number of other natural occurring brain peptides were ineffective at concentrations of 1 X 10(-6) M. Several somatostatin analogues were tested and their activity on the vas deferens was found to more closely parallel their potency to inhibit the release of gastric acid than of growth hormone. In contrast to the brain opiates, however, the inhibitory effects of VIP, somatostatin and its analogues, and HPP were not reversed by the opiate antagonist naloxone. The results suggest that the vas deferens can be readily used for evaluation of analogues of VIP, somatostatin, and other peptides.

Human pancreatic polypeptide inhibits insulin release in the rat

Summary Synthetic human pancreatic polypeptide (hPP) administered intravenously suppressed hepatic portal insulin levels in a dose-dependent manner in both fed and fasted rats. No effect on glucagon levels was detected. The C-terminal hexapeptide (hPP 31–36 ) and the C-terminal decapeptide (hPP 27–36 ) exhibited no effect on insulin levels in fed rats at molar doses significantly higher than the effective doses of hPP. A physiological role for hPP in the control of insulin is suggested.

Use of the Mouse Vas deferens Assay to Evaluate the Action of Somatostatin Peptides on Gastric Acid Secretion

Six closely related analogues of somatostatin were tested for their ability to inhibit electrically induced contractions of the mouse vas deferens. Their inhibiting activities tended to parallel their reported effects on gastric acid secretion in vivo, while no correlation to their in vitro growth hormone release-inhibiting activities was observed. It is suggested that information derived from the vas deferens assay may provide a relatively rapid and inexpensive assessment of the effects of somatostatin analogues on gastric acid secretion. The vas deferens assay was also used to test several somatostatin analogues for antagonistic activity, which was not found.

Hypothalamic Hormones Regulating Pituitary (and Other) Functions: Their Physiology and Biochemistry as Well as Recent Studies with Their Synthetic Analogues

It is well established now that the hypothalamic releasing and inhibitory hormones produced in the neuronal cell bodies regulate the secretory activity of the anterior pituitary gland. The discovery of several of these hormones and their isolation, structural identification and synthesis furnished the evidence for the theory of neurohumoral control of the pituitary gland put forward by Harris (1) and others.