Masaru Okuno

Peptide YY enhances NaCl and water absorption in the rat colon in vivo

Peptide YY (PYY) is thought to possess paracrine and endocrine functions. The highest concentrations of this peptide are in the colonic mucosa. The effect of PYY on electrolyte and water transport in the rat colon was studied in vivo. Under urethane anesthesia, rat colonic loops were perfused at a constant rate with physiological buffer solution containing phenol red as a nonabsorbable volume marker, and net movements of water, sodium, chloride and potassium in the perfused colon were determined every 10 min. Intravenous administration of PYY produced a dose-dependent increase in the net absorption of sodium chloride and water, as well as a decrease in the net secretion of potassium. PYY inhibited the reduction in net absorption of sodium chloride and water evoked by vasoactive intestinal peptide (VIP), but did not affect the VIP-evoked increase in net potassium secretion. These findings suggest that PYY acts as an enhancer of sodium chloride and water absorption and as an antagonist to VIP-induced secretion in the colon.

Gastric T-cell lymphoma presenting with epithelioid granulomas mimicking tuberculosis in regional lymph nodes.

Abstract: In patients with malignant lymphomas, a sarcoid reaction is occasionally observed. However, lymphoma-related granulomas with caseous necrosis are rare. We describe such a case of T-cell gastric lymphoma that was difficult to diagnose. A 50-year-old man was referred to our hospital because of abnormal gastric endoscopic findings: hypertrophic folds with narrowing of the gastric lumen and multiple ulcers in the body. Gastric biopsy specimens showed non-specific inflammation. An open biopsy of the enlarged gastric regional lymph nodes was performed. The sections revealed effacement of the normal architecture and replacement by numerous epithelioid granulomas accompanied by Langhans type giant cells with or without central caseous necrosis, strongly suggesting tuberculosis. However, mycobacteria and other causative organisms were not detected, and an anti-tuberculous regimen was ineffective. Repeat gastric biopsies were performed and, finally, atypical lymphocytes were observed infiltrating the mucosa. The patient was diagnosed with gastric T-cell lymphoma based on the results of immunohistochemical stainings. After chemotherapy, a total gastrectomy was performed. The diagnosis of gastric T-cell lymphoma with a sarcoid reaction was confirmed by histological findings of the sections. Namely, the gastric wall was replaced by atypical lymphocytes showing the phenotype of helper T cells, admixed with epithelioid granulomas with Langhans type giant cells. Thus, this case suggests that regional lymph nodes in gastric lymphomas may be present as epithelioid granulomas with caseous necrosis, mimicking tuberculosis.

Peptide YY-induced alteration of colonic electrolyte transport in the rat

The effect of peptide YY (PYY) on active electrolyte transport in rat colon was studied under short-circuited conditions. PYY (10(-6) M) decreased the basal short-circuit current (Isc) in both the distal and proximal segments of the colon. The decrease in Isc induced by PYY in the distal colon was about 3 times larger than that in the proximal colon. The response to PYY was inhibited by diphenylamine 2-carboxylate, a specific blocker of the Cl-channel, but not by amiloride, a Na-channel blocker. Unidirectional flux measurements in the distal colon revealed that PYY increased the net Na and Cl absorption and decreased the serosal-to-mucosal Cl flux. PYY inhibited the neurally mediated secretory response to electrical field stimulation in a concentration-dependent manner. PYY was also shown to reduce the direct action of the cholinergic agonist bethanechol on the epithelium. These results suggest that PYY inhibits electrogenic Cl secretion and stimulates electroneutral NaCl absorption via both presynaptic and postsynaptic sites in the distal colon.

Prostaglandins D2 diminishes transmucosal potential difference in rat colonic mucosa in vitro in contrast to the increasing effect of prostaglandin E1

The effect of Prostaglandin D2 (PGD2) on ion transport was investigated in the rat colon in vitro. Ion transport across the intestinal mucosa was estimated by transmucosal potential difference (PD) and short circuit current (Isc) in the Ussing chamber. PGD2 added to the serosal reservoir induced a sustained reduction in PD and Isc at the concentration of higher than 10(-7)M, producing the maximal decrease at 10(-5)M. PGD2 at 10(-5)M completely blocked the increase in PD elicited by prostaglandin E1 (PGE1), theophylline, dibutyryl cAMP or serotonin. Adenylate cyclase activity was determined in the colonic mucosal homogenates after addition of PGD2 and PGE1. Treatment with PGD2 or PGE1 caused a significant increase in the enzyme activity. Combined treatment with both prostaglandins induced no more increase than that elicited by PGE1 alone. These results suggest that PGD2 has an anti-secretory effect on the rat colon and it may regulate the ion transport process through other mechanism than the modification of cyclic AMP concentration in mucosal cells.

Marked secretion of pyruvate in human duodenal juice stimulated with pancreozymin or secretin

Pyruvate and lactate in duodenal aspirates were investigated to determine whether they are excreted from human pancreas as substrates for alkaline secretion as is bicarbonate. Secretion of these acids was compared with that of another organic acid, citrate, which is thought to be excreted in close relationship to digestive enzymes. All acids were assayed in the fluid obtained from 11 subjects without pancreatic diseases, before and after sequential intravenous injections of 1 unit/kg pancreozymin and 1 unit/kg secretin. Pyruvate concentrations were markedly increased by each stimulation, especially by secretin, and the cumulative excretions of pyruvate and bicarbonate after secretin stimulation were significantly correlated among the subjects. In contrast, lactate concentrations, although high just after administration of pancreozymin, declined to a considerable extent following each injection, rather similar to those of protein or citrate. These data suggest that pyruvate may be secreted from human pancreatic duct cells similar to bicarbonate secretion through mechanisms related to alkaline secretion.

Abstracts of Selected Papers Presented at the 76th General Meeting of the Japanese Society of Gastroenterology

S OF SELECTED PAPERS PRESENTED AT THE 76TH GENERAL MEETING OF THE JAPANESE SOCIETY OF GASTROENTEROLOGY March 29-31, 1990, Tokyo, Japan Chairman: Haruo KAMEDA, M.D.