Biomedical subjects
P L Rayford
Publications and source records attributed to P L Rayford.
Effect of osmolality on gastric acid secretion and gastric emptying in man.
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Effects of hypophysectomy and hypophysectomy plus growth hormone on secretin release and on concentrations of secretin in the duodenal mucosa.
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Rate of disappearance of circulating endogenous gastrin in dogs.
In five awake mongrel dogs, endogenous gastrin was released by continuous irrigation of the antrum with acetylcholine. After 60 minutes of antral perfusion, the entire vascular supply of the antrum was suddenly and totally occluded, and serial samples of peripheral blood were taken for measurement of gastrin. The rate of disappearance of endogenous gastrin was caluclated by standard linear regression analysis; the calculated half-life of endogenous gastrin was 8.62 minutes. Analysis of the data suggests that the disappearance rate of endogenous gastrin could be explained by two distinct half-lives: one of 2.8 minutes (which is similar to the half-time in dogs of both 14- and 17 -amino acid gastrin), and another of 15.4 minutes (which is similar to the half-time of 34 -amino acid gastrin). Physiologically released gastrin is a mixture of three or more molecular forms of gastrin and the half-life of 8.62 minutes probably represents the disappearance half-time of this mixture.
Effect of alcohol on the release of secretin and pancreatic secretion.
The effect of alcohol on the release of secretin was studied in man by radioimmunoassay, and in dogs and cats by radioimmunoassay and bioassay (secretion of water and bicarbonate by the pancreas). In man plasma secretin levels increased significantly from a basal of 121 +/- 14 to 164 +/- 24 pg/ml at 60 minutes after oral ingestion of alcohol. Intraduodenal administration of alcohol in man, dogs, and cats did not release secretin or affect pancreatic water and bicarbonate secretion in dogs and cats, but a moderate increase in pancreatic protein output was observed in these two species. Plasma gastrin levels rose significantly from a basal of 52 +/- 4 to 64 +/- 3 pg/ml after ingestion of alcohol in man and from 33 +/- 5 to 51 +/- 8 pg/ml after administration of alcohol into the stomach of dogs. Administration of alcohol into the duodenum in man, dogs, and cats did not release gastrin. We conclude that alcohol probably does not release secretin directly. The mechanism of release of secretin in man is unknown; it clearly involves the stomach and may be mediated via the release of gastric acid.
Secretin, cholecystokinin and newer gastrointestinal hormones (second of two parts).
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Secretin, cholecystokinin and newer gastrointestinal hormones (first of two parts).
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Suppression of gastric secretion and serum gastrin by gastrin antibody.
Fourteen dogs received varying doses of antigastrin antibody; after a single dose of 0.07 ml/kg, circulating gastrin levels could not be measured for as long as forty-seven days. Gastric secretion in response to food was not diminished by antigastrin antibody doses as high as 0.07 ml/kg daily for ten days. Larger doses, 0.2 and 0.4 ml/kg, were required to produce a temporary reduction in gastric-stimulated gastric acid secretion. Mucosal levels of gastrin in the antrum, fundus, and duodenum were greatly increased ten days after injection of antigastrin antibody. The therapeutic use of antigastrin antibody to control gastric secretion seems at the present time not feasible because of the scarcity of the antigastrin antibody and because large doses aare required to obtain only a temporary effect.
Gonadotropins and their subunits: basic and clinical studies.
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Suppression of gastrin release and gastric secretion by gastric inhibitory polypeptide (GIP) and vasoactive intestinal polypeptide (VIP).
Five dogs prepared with Heidenhain pouches received infusions of saline, GIP and VIP before and after a standard meat meal. Blood samples were obtained under basal conditions and at subsequent intervals for measurement of gastrin, insulin, GIP and VIP by radioimmunoassay. GIP and VIP infusions had no effect on basal levels of gastrin. GIP and VIP (in common with secretin and glucagon) were found to suppress food-stimulated release of gastrin and gastrin-stimulated acid secretion from the Heidenhain pouch. Insulin levels were significantly elevated during GIP and VIP infusions. Food released GIP (and perhaps VIP.
Disappearance half-time of endogenous and exogenous secretin in dogs.
We have used a sensitive and specific radioimmunoassay to measurespectively. the disappearance half-times of exogenous porcine secretin and endogenous canine secretin in the dog and found them to be 2-45 and 2-85 minutes, respectively.
Patterns of molecular forms of gastrin in antral mucosa and antral serum.
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Effect of bombesin on serum gastrin and cholecystokinin in dogs.
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Effect of prostaglandin E1 on plasma secretin and pancreatic exocrine function in dogs.
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Determination of secretin levels in mucosa by radiommunoassay.
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Plasma levels of secretin in man and dogs: validation of a secretin radioimmunoassay.
We have developed and validated a secretin radioimmunoassay that is sufficiently sensitvie to measure circulating levels of secretin in the plasma of man and dogs. At a final dilution of 1:50,000, the antibody bound 30 percent to 40 percent of radioiodinated (125 I) 6-tyrosyl synthetic secretin. Pure natural porcine secretin was used as a reference standard and a linear dose-response curve was generated with 10 to 1,000 pg. of the polypeptide. Little or no cross-reactivity was found when graded doses of other gastrointestinal polypeptides were assayed in the radioimmunoassay and immunoreactive secretin (IRS) in volumes of serum up to 300 mul could be measured accurately.
Effect of glucagon on pancreatic exocrine secretion and secretin release.
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Catabolism of secretin by the liver and kidney.
We have investigated the roles of the liver and the kidney in the catabolism of secretin, using a specific and sensitive radioimmunoassay. Dogs were prepared with sampling catheters in the aorta, hepatic vein, portal vein, and renal vein and with electromagnetic flow probes on the portal vein, hepatic artery, and renal artery. Secretin levels in the vessels entering and leaving the liver and kidney were determined by radioimmunoassay and the total mass of secretin [concentration (picograms per milliliter) X plasma flow rate (milliliter per minute)] was calculated during an intravenous infusion of exogenous secretin and during release of endogenous secretin by acidification of the proximal intestine. The total masses of secretin entering and leaving the liver were the same during secretin infusion and during the release of endogenous secretin. Under conditions of elevation of plasma secretin, however, the kidney extracted 30 percent of arterial secretin during secretin infusion and 45 percent during release of endogenous secretin. Clearly the kidney is a major site of secretin catabolism.