Effects of a sucrose-enriched diet on the pattern of gene expression, contraction and Ca(2+) transport in Goto-Kakizaki type 2 diabetic rat heart.

There has been a spectacular rise in the global prevalence of type 2 diabetes mellitus (T2DM), and cardiovascular disease is the major cause of morbidity and mortality in diabetic patients. A variety of diastolic and systolic dysfunctions have been demonstrated in type 2 diabetic heart. The consumption of sugar-sweetened beverages has been linked to rising rates of obesity, which in turn is a risk factor for development of T2DM. In this study, the effects of a sucrose-enriched diet on the pattern of gene expression, contraction and Ca(2+) transport in the Goto-Kakizaki T2DM rat heart were investigated. Genes encoding cardiac muscle proteins (Myh7, Mybpc3, Myl1, Myl3 and Mylpf), intercellular proteins (Gja4), cell membrane transport (Atp1b1), calcium channels (Cacna1c, Cacna1g and Cacnb1) and potassium channels (Kcnj11) were upregulated and genes encoding potassium channels (Kcnb1) were downregulated in GK compared with control rats. Genes encoding cardiac muscle proteins (Myh6, Mybpc3 and Tnn2), intercellular proteins (Gja1 and Gja4), intracellular Ca(2+) transport (Atp2a1 and Ryr2), cell membrane transport (Atp1a2 and Atp1b1) and potassium channel proteins (Kcnj2 and Kcnj8) were upregulated and genes encoding cardiac muscle proteins (Myh7) were downregulated in control rats fed sucrose compared with control rats. Genes encoding cardiac muscle proteins (Myh7) and potassium channel proteins (Kcnj11) were downregulated in control and GK rats fed sucrose compared with control and GK rats, respectively. The amplitude of shortening was reduced in myocytes from the control-sucrose group compared with control rats and in the GK-sucrose group compared with GK rats. The amplitude of the Ca(2+) transient was increased in myocytes from control-sucrose compared with control rats and decreased in GK-sucrose compared with GK rats. Subtle alterations in the pattern of expression of genes encoding a variety of cardiac muscle proteins are associated with changes in shortening and intracellular Ca(2+) transport in ventricular myocytes from GK T2DM and control rats fed a sucrose-enriched diet.

Effects of exercise training on excitation-contraction coupling and related mRNA expression in hearts of Goto-Kakizaki type 2 diabetic rats.

Although, several novel forms of intervention aiming at newly identified therapeutic targets are currently being developed for diabetes mellitus (DM), it is well established that physical exercise continues to be one of the most valuable forms of non-pharmacological therapy. The aim of the study was to investigate the effects of exercise training on excitation-contraction coupling and related gene expression in the Goto-Kakizaki (GK) type 2 diabetic rat heart and whether exercise is able to reverse diabetes-induced changes in excitation-contraction coupling and gene expression. Experiments were performed in GK and control rats aged 10-11 months following 2-3 months of treadmill exercise training. Shortening, [Ca(2+)]i and L-type Ca(2+) current were measured in ventricular myocytes with video edge detection, fluorescence photometry and whole cell patch clamp techniques, respectively. Expression of mRNA was assessed in ventricular muscle with real-time RT-PCR. Amplitude of shortening, Ca(2+) transients and L-type Ca(2+) current were not significantly altered in ventricular myocytes from GK sedentary compared to control sedentary rats or by exercise training. Expression of mRNA encoding Tpm2, Gja4, Atp1b1, Cacna1g, Cacnb2, Hcn2, Kcna3 and Kcne1 were up-regulated and Gja1, Kcnj2 and Kcnk3 were down-regulated in hearts of sedentary GK rats compared to sedentary controls. Gja1, Cav3 and Kcnk3 were up-regulated and Hcn2 was down-regulated in hearts of exercise trained GK compared to sedentary GK controls. Ventricular myocyte shortening and Ca(2+) transport were generally well preserved despite alterations in the profile of expression of mRNA encoding a variety of cardiac muscle proteins in the adult exercise trained GK diabetic rat heart.

Rectal taurocholate increases L cell and insulin secretion, and decreases blood glucose and food intake in obese type 2 diabetic volunteers.

AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are secreted from enteroendocrine L cells in response to numerous stimuli, including bile salts. Both have multiple effects that are potentially useful in treating diabetes and obesity. L cell number and hormone content in the intestine are highest in the rectum in humans. We investigated the effects of intrarectal sodium taurocholate on plasma GLP-1, PYY, insulin and glucose concentrations, and on food intake of a subsequent meal. METHODS: Ten obese type 2 diabetic volunteers were each studied on five separate occasions after an overnight fast and oral administration of 100 mg sitagliptin 10 h before the study. They then received an intrarectal infusion of either one of four doses of taurocholate (0.66, 2, 6.66 or 20 mmol, each in 20 ml of vehicle) or vehicle alone (1% carboxymethyl cellulose) single-blind over 1 min. Hormone and glucose measurements were made prior to, and for 1 h following, the infusion. The consumption of a previously selected favourite meal eaten to satiety was measured 75 min after the infusion. RESULTS: Taurocholate dose-dependently increased GLP-1, PYY and insulin, with 20 mmol doses resulting in peak concentrations 7.2-, 4.2- and 2.6-fold higher, respectively, than those achieved with placebo (p < 0.0001 for each). Plasma glucose decreased by up to 3.8 mmol/l (p < 0.001). Energy intake was decreased dose-dependently by up to 47% (p < 0.0001). The ED(50) values for effects on integrated GLP-1, insulin, PYY, food intake and glucose-lowering responses were 8.1, 10.5, 18.5, 24.2 and 25.1 mmol, respectively. CONCLUSIONS/INTERPRETATION: Therapies that increase bile salts (or their mimics) in the distal bowel may be valuable in the treatment of type 2 diabetes and obesity.

Shortening and intracellular Ca2+ in ventricular myocytes and expression of genes encoding cardiac muscle proteins in early onset type 2 diabetic Goto-Kakizaki rats.

There has been a spectacular rise in the global prevalence of type 2 diabetes mellitus. Cardiovascular complications are the major cause of morbidity and mortality in diabetic patients. Contractile dysfunction, associated with disturbances in excitation-contraction coupling, has been widely demonstrated in the diabetic heart. The aim of this study was to investigate the pattern of cardiac muscle genes that are involved in the process of excitation-contraction coupling in the hearts of early onset (8-10 weeks of age) type 2 diabetic Goto-Kakizaki (GK) rats. Gene expression was assessed in ventricular muscle with real-time RT-PCR; shortening and intracellular Ca(2+) were measured in ventricular myocytes with video edge detection and fluorescence photometry, respectively. The general characteristics of the GK rats included elevated fasting and non-fasting blood glucose and blood glucose at 120 min following a glucose challenge. Expression of genes encoding cardiac muscle proteins (Myh6/7, Mybpc3, Myl1/3, Actc1, Tnni3, Tnn2, Tpm1/2/4 and Dbi) and intercellular proteins (Gja1/4/5/7, Dsp and Cav1/3) were unaltered in GK ventricle compared with control ventricle. The expression of genes encoding some membrane pumps and exchange proteins was unaltered (Atp1a1/2, Atp1b1 and Slc8a1), whilst others were either upregulated (Atp1a3, relative expression 2.61 ± 0.69 versus 0.84 ± 0.23) or downregulated (Slc9a1, 0.62 ± 0.07 versus 1.08 ± 0.08) in GK ventricle compared with control ventricle. The expression of genes encoding some calcium (Cacna1c/1g, Cacna2d1/2d2 and Cacnb1/b2), sodium (Scn5a) and potassium channels (Kcna3/5, Kcnj3/5/8/11/12, Kchip2, Kcnab1, Kcnb1, Kcnd1/2/3, Kcne1/4, Kcnq1, Kcng2, Kcnh2, Kcnk3 and Kcnn2) were unaltered, whilst others were either upregulated (Cacna1h, 0.95 ± 0.16 versus 0.47 ± 0.09; Scn1b, 1.84 ± 0.16 versus 1.11 ± 0.11; and Hcn2, 1.55 ± 0.15 versus 1.03 ± 0.08) or downregulated (Hcn4, 0.16 ± 0.03 versus 0.37 ± 0.08; Kcna2, 0.35 ± 0.03 versus 0.80 ± 0.11; Kcna4, 0.79 ± 0.25 versus 1.90 ± 0.26; and Kcnj2, 0.52 ± 0.07 versus 0.78 ± 0.08) in GK ventricle compared with control ventricle. The amplitude of ventricular myocyte shortening and the intracellular Ca(2+) transient were unaltered; however, the time-to-peak shortening was prolonged and time-to-half decay of the Ca(2+) transient was shortened in GK myocytes compared with control myocytes. The results of this study demonstrate changes in expression of genes encoding various excitation-contraction coupling proteins that are associated with disturbances in myocyte shortening and intracellular Ca(2+) transport.

Contractility of ventricular myocytes is well preserved despite altered mechanisms of Ca2+ transport and a changing pattern of mRNA in aged type 2 Zucker diabetic fatty rat heart.

There has been a spectacular rise in the global prevalence of type 2 diabetes mellitus and cardiovascular complications are the major cause of morbidity and mortality in diabetic patients. The objective of the study was to investigate ventricular myocyte shortening, intracellular Ca(2+) signalling and expression of genes encoding cardiac muscle proteins in the aged Zucker diabetic fatty (ZDF) rat. There was a fourfold elevation in non-fasting blood glucose in ZDF rats (478.43 ± 29.22 mg/dl) compared to controls (108.22 ± 2.52 mg/dl). Amplitude of shortening, time to peak (TPK) and time to half (THALF) relaxation of shortening were unaltered in ZDF myocytes compared to age-matched controls. Amplitude and THALF decay of the Ca(2+) transient were unaltered; however, TPK Ca(2+) transient was prolonged in ZDF myocytes (70.0 ± 3.2 ms) compared to controls (58.4 ± 2.3 ms). Amplitude of the L-type Ca(2+) current was reduced across a wide range of test potentials (-30 to +40 mV) in ZDF myocytes compared to controls. Sarcoplasmic reticulum Ca(2+) content was unaltered in ZDF myocytes compared to controls. Expression of genes encoding cardiac muscle proteins, membrane Ca(2+) channels, and cell membrane ion transport and intracellular Ca(2+) transport proteins were variously altered. Myh6, Tnnt2, Cacna2d3, Slc9a1, and Atp2a2 were downregulated while Myl2, Cacna1g, Cacna1h, and Atp2a1 were upregulated in ZDF ventricle compared to controls. The results of this study have demonstrated that preserved ventricular myocyte shortening is associated with altered mechanisms of Ca(2+) transport and a changing pattern of genes encoding a variety of Ca(2+) signalling and cardiac muscle proteins in aged ZDF rat.

Changing pattern of gene expression is associated with ventricular myocyte dysfunction and altered mechanisms of Ca2+ signalling in young type 2 Zucker diabetic fatty rat heart.

The association between type 2 diabetes and obesity is very strong, and cardiovascular complications are the major cause of morbidity and mortality in diabetic patients. The aim of this study was to investigate early changes in the pattern of genes encoding cardiac muscle regulatory proteins and associated changes in ventricular myocyte contraction and Ca(2+) transport in young (9- to 13-week-old) type 2 Zucker diabetic fatty (ZDF) rats. The amplitude of myocyte shortening was unaltered; however, time-to-peak shortening and time to half-relaxation of shortening were prolonged in ZDF myocytes (163 ± 5 and 127 ± 7 ms, respectively) compared with age-matched control rats (136 ± 5 and 103 ± 4 ms, respectively). The amplitude of the Ca(2+) transient was unaltered; however, time-to-peak Ca(2+) transient was prolonged in ZDF myocytes (66.9 ± 2.6 ms) compared with control myocytes (57.6 ± 2.3 ms). The L-type Ca(2+) current was reduced, and inactivation was prolonged over a range of test potentials in ZDF myocytes. At 0 mV, the density of L-type Ca(2+) current was 1.19 ± 0.28 pA pF(-1) in ZDF myocytes compared with 2.42 ± 0.40 pA pF(-1) in control myocytes. Sarcoplasmic reticulum Ca(2+) content, release and uptake and myofilament sensitivity to Ca(2+) were unaltered in ZDF myocytes compared with control myocytes. Expression of genes encoding various L-type Ca(2+) channel proteins (Cacna1c, Cacna1g, Cacna1h and Cacna2d1) and cardiac muscle proteins (Myh7) were upregulated, and genes encoding intracellular Ca(2+) transport regulatory proteins (Atp2a2 and Calm1) and some cardiac muscle proteins (Myh6, Myl2, Actc1, Tnni3, Tnn2, and Tnnc1) were downregulated in ZDF heart compared with control heart. A change in the expression of genes encoding myosin heavy chain and L-type Ca(2+) channel proteins might partly underlie alterations in the time course of contraction and Ca(2+) transients in ventricular myocytes from ZDF rats.

Neuropeptide Y distribution in the rat brain.

A massive neuronal system was detected by immunocytochemistry and radioimmunoassay with antibodies to neuropeptide Y, the recently isolated peptide of the pancreatic polypeptide family. Immunoreactive cell bodies and fibers were most prevalent in cortical, limbic, and hypothalamic regions. Neuropeptide Y was extracted in concentrations higher than those of any other peptide hitherto discovered in the mammalian brain. Column chromatography of brain extracts and double immunostaining experiments indicate that neuropeptide Y is the endogenous brain peptide responsible for immunostaining of pancreatic polypeptide-like immunoreactivity in the mammalian brain.

BLT2 is expressed in PanINs, IPMNs, pancreatic cancer and stimulates tumour cell proliferation.

Pancreatic cancer has an abysmal prognosis. Targets for early detection, prevention and therapy are desperately needed. Inflammatory pathways have an important impact on tumour growth and progression. Expression of BLT2 (the second leukotriene B(4) receptor) was investigated by real-time RT-PCR and immunohistochemistry. Cell proliferation was studied after stable transfection with BLT2, after treatment with siRNA and Compound A as an agonist. BLT2 is expressed in all pancreatic cancer cell lines. Results from real-time RT-PCR revealed significant overexpression of BLT2 in malignant intraductal papillary mucinous neoplasias (IPMNs) and pancreatic adenocarcinoma. Intense staining was evident in IPMNs, infiltrating tumour cells and advanced pancreatic intraepithelial neoplasias (PanINs) but not in normal ductal cells. Overexpression of BLT2 as well as stimulation of Colo357, Panc-1 and AsPC1 cells with Compound A caused a significant increase in tumour cell proliferation, an effect reversed after siRNA treatment. This study demonstrates for the first time the expression of BLT2 in the pancreas and overexpression in pancreatic cancers and malignant IPMNs in particular. Upregulation of BLT2 is already evident in precursor lesions (PanINs, IPMNs). Overexpression of this receptor leads to significant growth stimulation. Therefore, we suggest BLT2 as a new target for chemoprevention and therapy for pancreatic cancer.

The Pattern of mRNA Expression Is Changed in Sinoatrial Node from Goto-Kakizaki Type 2 Diabetic Rat Heart.

BACKGROUND: In vivo experiments in Goto-Kakizaki (GK) type 2 diabetic rats have demonstrated reductions in heart rate from a young age. The expression of genes encoding more than 70 proteins that are associated with the generation and conduction of electrical activity in the GK sinoatrial node (SAN) have been evaluated to further clarify the molecular basis of the low heart rate. MATERIALS AND METHODS: Heart rate and expression of genes were evaluated with an extracellular electrode and real-time RT-PCR, respectively. Rats aged 12-13 months were employed in these experiments. RESULTS: Isolated spontaneous heart rate was reduced in GK heart (161 ± 12 bpm) compared to controls (229 ± 11 bpm). There were many differences in expression of mRNA, and some of these differences were of particular interest. Compared to control SAN, expression of some genes were downregulated in GK-SAN: gap junction, Gja1 (Cx43), Gja5 (Cx40), Gjc1 (Cx45), and Gjd3 (Cx31.9); cell membrane transport, Trpc1 (TRPC1) and Trpc6 (TRPC6); hyperpolarization-activated cyclic nucleotide-gated channels, Hcn1 (HCN1) and Hcn4 (HCN4); calcium channels, Cacna1d (Cav1.3), Cacna1g (Cav3.1), Cacna1h (Cav3.2), Cacna2d1 (Cavα2δ1), Cacna2d3 (Cavα2δ3), and Cacng4 (Cav γ 4); and potassium channels, Kcna2 (Kv1.2), Kcna4 (Kv1.4), Kcna5 (Kv1.5), Kcnb1 (Kv2.1), Kcnd3 (Kv4.3), Kcnj2 (Kir2.1), Kcnk1 (TWIK1), Kcnk5 (K2P5.1), Kcnk6 (TWIK2), and Kcnn2 (SK2) whilst others were upregulated in GK-SAN: Ryr2 (RYR2) and Nppb (BNP). CONCLUSIONS: This study provides new insight into the changing expression of genes in the sinoatrial node of diabetic heart.

Frondoside A potentiates the effects of conventional therapeutic agents in acute leukemia.

Acute leukemia is the major cause of mortality in hematological malignancies. Despite improvement of survival with current chemotherapies, patients die from the disease or side-effects of treatment. Thus, new therapeutic agents are needed. Frondoside A is a triterpenoid glycoside originally isolated from the sea cucumber, Cucumaria frondosa that has potent antitumor effects in various cancers. The current study investigated the effects of frondoside A in acute leukemia cell lines alone and in combination with drugs used for this malignancy. This study is the first comparing the efficacy of frondoside A to available conventional drugs. The acute leukemia cell lines used were CCRF-CEM, HL-60 and THP-1. Cells were cultured and treated with different concentrations of vincristine sulphate, asparaginase and prednisolone alone and in combination with frondoside A. The inhibitory concentration 50 (IC50) for each compound was determined for the cell lines. CCRF-CEM cells were very sensitive to frondoside A treatment while HL-60 and THP1 were less sensitive. Frondoside A markedly enhanced the anticancer effects of all of the conventional drugs. Synergistic effects were seen with most of the combinations. Frondoside A may be valuable in the treatment of acute leukemia, particularly when used in combination with current therapeutic drugs.

How to build a pancreas.

Pancreatic Growth and Regeneration Edited by Nora Sarvetnick. Basel, Karger, 1997, CHF113.0/DEM135.00/$98.00 (xiv+250 pages) ISBN 3-8055-6618-2.

Chronic low dose islet amyloid polypeptide infusion reduces food intake, but does not influence glucose metabolism, in unrestrained conscious rats: studies using a novel aortic catheterization technique.

Islet amyloid polypeptide (IAPP) is a 37-amino acid polypeptide coproduced with insulin in the beta-cells of the pancreatic islets. The physiological effects of IAPP have not been established. Although effects on glucose metabolism are seen only at pharmacological doses both in vitro and in vivo, effects on food intake have been shown at near-physiological concentrations. The aim of the present study was to investigate the effects of similar elevations of circulating plasma IAPP levels on glucose metabolism in rats and to evaluate the function of a novel aortic catheterization technique. In a cross-over design, two sets of experiments in which conscious unrestrained rats received chronic IAPP infusions at 0 and 2 or 0 and 7 pmol/kg min were performed. Peripheral glucose disposal was determined by means of the hyperinsulinemic euglycemic clamp technique. Chronic elevations of circulating IAPP at concentrations that reduced food intake [43.5 +/- 6.2 g (control) vs. 35.7 +/- 8.2 g (IAPP; P < 0.01) and 34.0 +/- 2.2 g (control) vs. 28.8 +/- 1.4 g (IAPP; P = 0.07) for the 7 and 2 pmol/kg x min experiments, respectively] had no effect on the glucose metabolic rate [GMR; 18.5 +/- 0.6 mmol/kg x h (control) vs. 18.7 +/- 0.9 mmol/kg x h (IAPP) and 14.4 +/- 0.7 mmol/kg x h (control) vs. 15.6 +/- 0.7 mmol/kg x h (IAPP) for the 7 and 2 pmol/kg x min experiments, respectively]. Thus, effects on glucose metabolism are unlikely to explain the anorectic effect of IAPP.

Distribution and immunocytochemical colocalization of peptide YY and enteroglucagon in endocrine cells of the rabbit colon.

Peptide YY (PYY) is 36 amino acid peptide hormone present in high concentrations in the colon where it is colocalized with enteroglucagon in L cells. A selective release of PYY and enteroglucagon from the rabbit colon has been described, raising the question of the exact localization of the two hormones in the rabbit colon. We have therefore examined the distribution of PYY and enteroglucagon as well as somatostatin in the rabbit colon using RIA and electron microscopic immunocytochemistry. PYY and enteroglucagon were present in high concentrations in the colorectal mucosa with peak concentrations in the left colon (PYY 544 +/- 87 pmol/g, enteroglucagon 152 +/- 10 pmol/g). Electron microscopic examination of the colonic mucosa demonstrated a large population (65%) of EC cells, a moderate population (30%) of L cells, and a small population (5%) of D cells. By immunogold labeling serotonin was localized to EC cells, PYY and enteroglucagon to L cells, and somatostatin to the D cell. Double immunogold labeling revealed PYY and enteroglucagon in all L cells examined (93 cells). A majority of the secretory granules (83%) were labeled by both PYY and glucagon antibodies, whereas a significant portion of granules (15%) was labeled by the PYY antibodies alone. The results demonstrate that L cells are the sole source of PYY and enteroglucagon in the rabbit colon and that L cells contain different populations of secretory granules. The existence of different secretory granules in L cells may explain the selective release of PYY and enteroglucagon observed in the rabbit colon.

The intracellular mechanism of insulin resistance in pancreatic cancer patients.

The diabetes that frequently occurs in pancreatic cancer patients is characterized by profound peripheral insulin resistance. The intracellular mechanism of this insulin resistance was investigated in skeletal muscle biopsies from pancreatic cancer patients with or without diabetes and control subjects. Insulin receptor (IR) binding, tyrosine kinase activity, IR messenger RNA (mRNA), IR substrate-1 content, GLUT-4, and GLUT-4 mRNA content were all normal in pancreatic cancer patients. In contrast, multiple defects in glycogen synthesis were found in pancreatic cancer patients, especially in those with diabetes. Glycogen synthase I activity, total activity, and mRNA levels were significantly decreased in pancreatic cancer patients compared with controls. The fractional velocity of glycogen synthase was decreased only in the diabetic pancreatic cancer group. Glycogen phosphorylase a and b activities were increased in diabetic pancreatic cancer patients, but glycogen phosphorylase mRNA levels were not significantly different. The insulin resistance associated with pancreatic cancer is associated with a post-IR defect, which impairs skeletal muscle glycogen synthesis and glycogen storage.

Neurotensin infusion in man: pharmacokinetics and effect on gastrointestinal and pituitary hormones.

Synthetic neurotensin was infused into five healthy subjects at a mean dose of 2.3 pmol/kg . min for 30 min, producing a rise in plasma neurotensin concentrations, measured by RIA of 104 +/- 10 (mean +/- SEM) pmol/liter. The mean disappearance half-time on stopping the infusion was 3.8 +/- 0.2 min. The MCR was 16 +/- 1 ml/kg . min, and the apparent space of distribution was 88 +/- 6 ml/kg. During the neurotensin infusions, plasma pancreatic polypeptide rose by 145 +/- 54 pmol/liter. In contrast to results in experimental animals, there was no significant change in the pulse or blood pressure of the subjects or any significant change in blood glucose or plasma concentrations of insulin, glucagon, gastric inhibitory peptide, gastrin, motilin, or vasoactive intestinal peptide. Similarly, there was no change in plasma concentrations of TSH, GH, PRL, LH, and FSH.

Pancreatic tumours produce neurotensin.

Tumour tissue may secrete substances which are not normally secreted by the original tissue. We have found that 6 out of 21 pancreatic tumours producing vasoactive intestinal peptide also produce neurotensin-like peptides. These are sometimes secreted and very high plasma levels of neurotensin-like immunoreactivity may be found in the circulation.

Localization and molecular forms of galanin in human adrenals: elevated levels in pheochromocytomas.

Galanin immunoreactivity was measured by RIA, using antibodies directed against both the non-C- and C-terminal positions of porcine galanin, in tissue extracts of normal adrenals and pheochromocytomas and also in the plasma of normal subjects and patients with pheochromocytomas. No C-terminal galanin-like immunoreactivity was detected in plasma or tissue, suggesting differences in the amino acid sequence of human compared with porcine galanin. A non-C-terminally directed antibody was, therefore, used to characterize human galanin immunoreactivity by gel permeation chromatography and reverse phase high pressure liquid chromatography and to localize it by immunocytochemistry. The galanin content of whole adrenal gland was 2.6 +/- 0.9 (+/- SEM) pmol/g (n = 5). In contrast, however, pheochromocytomas had much greater concentrations (21 +/- 2.3 pmol/g; n = 16). Gel chromatography and reverse phase high pressure liquid chromatography revealed 2 molecular forms of galanin immunoreactivity with identical elution positions in both normal adrenals and tumors. The concentration of galanin in plasma from both normal subjects and pheochromocytoma patients was below the detection limit of the assay (less than 10 pmol/liter). Using immunocytochemistry, galanin was localized to scattered cells or clusters of tumor cells in 5 of 11 pheochromocytomas and only a few chromaffin cells and cortical nerve fibers in normal adrenals.

Peptide YY kinetics and effects on blood pressure and circulating pancreatic and gastrointestinal hormones and metabolites in man.

Peptide YY (PYY) is a 36 amino acid peptide produced by mucosal endocrine cells of the ileum and colon which inhibits acid secretion and intestinal transit in man. To assess its effects on metabolites and digestive hormones PYY was infused into 18 fasting normal subjects at three dose levels (0.06, 0.19, and 0.57 pmol kg-1 min-1), each for a period of 1 h. During the infusions mean plasma PYY levels increased by 8, 25, and 73 pmol/liter, respectively. The mean disappearance half-time on stopping the infusions was 9.2 +/- 0.4 (SEM) min. The mean MCR was 7.3 +/- 0.7 ml kg-1 min-1 and the apparent volume of distribution was calculated to be 94 +/- 9 ml kg-1. During the highest dose infusion there was a significant increase in both systolic and diastolic blood pressure, of 8.6 +/- 3.7 mmHg (P less than 0.05) and 10.9 +/- 3.0 mmHg (P less than 0.01), respectively. PYY caused a significant 50% reduction in plasma pancreatic polypeptide concentrations (P less than 0.05) and a 55% reduction in circulating motilin levels (P less than 0.05). PYY had no significant effect on circulating concentrations of insulin, glucagon, gastrin, gastric inhibitory peptide, neurotensin, enteroglucagon, or vasoactive intestinal peptide. PYY also had no significant effect on circulating concentrations of glucose, lactate, glycerol, or nonesterified fatty acids. This recently discovered human intestinal hormonal peptide thus has significant effects both on gastrointestinal hormones (motilin and pancreatic polypeptide) and blood pressure in man, but appears not to influence glucose or lipid metabolism.

The effect of somatostatin analogs on secretion of growth, pancreatic, and gastrointestinal hormones in man.

The potency and specificity of somatostatin (SS) and four of its analogs were compared in seven patients with pancreatic endocrine tumors. The analogs tested were [D-Trp8]-SS, [D-Trp8, D-Cys14]-SS, Des-Asn5-[D-Trp8, D-Ser13]-SS, and Des (AA)1,2,4,5,12,13, [D-Trp8]-SS, and they did not show selective effects on the suppression of basal concentrations of GH, insulin, glucagon, pancreatic polypeptide, gastrin, gastric inhibitory peptide, motilin, enteroglucagon, or neurotensin. The observation that the potency of these analogs is similar to that of the parent molecule throws considerable light on the structure/activity relationship of the somatostatin molecule. Des-AA1,2,4,5,12,13, [D-Trp8]-Ss has been reported to have a prolonged action when administered sc. When administered iv, however, this octapeptide analog ws not long acting, suggesting that the prolonged action seen in the previous study was a result of delayed uptake from the injection site. An increment in plasma SS concentrations of 19 +/- 3 pmol/liter suppressed basal concentrations of GH, insulin, glucagon, and several gastrointestinal hormones by more than 50%, suggesting that even small changes in plasma SS levels may be physiologically important.

Bombesin: action on gut hormones and calcium in man.

Bombesin, a peptide with widespread biological actions, has been demonstrated in human tissues by immunological methods. To investigate its effect in man, synthetic bombesin was infused at low doses in six male volunteers. Bombesin at 2.4 pmol kg-1 min-1 produced significant rises in plasma insulin, glucagon, pancreatic polypeptide, gastrin, cholecystokinin, motilin, glucose-dependent insulinotropic polypeptide, neurotensin, enteroglucagon, vasoactive intestinal polypeptide, and serum calcium. In contrast, bombesin caused a profound fall in parathyroid hormone levels and reduced plasma glucose concentrations. A late rise in plasma calcitonin was also observed. Bombesin had no significant effect on the pituitary hormones, TSH, GH, PRL, or cortisol. No hormonal changes or alterations in calcium were noted during saline infusions. Bombesin has a marked stimulatory effect on gastrointestinal hormones, which is unique and opposite to the effect of somatostatin, a potent inhibitor of gut hormone release. Bombesin also influences calcium-regulating hormones, either directly or through its action on gut hormones. The bombesin concentrations achieved with the dosages used were low enough to indicate a possible physiological role for the endogenous peptide.