A unique case of central diabetes insipidus (DI) associated with transient pituitary stalk enlargement: close observation over several years using magnetic resonance imaging (MRI) and hypophysial endocrine tests.

We had the opportunity to closely observe a unique case of central diabetes insipidus (DI), in which dramatic changes in both radiological findings and hypophysial functions were seen. A 63-year-old female developed central DI, and magnetic resonance imaging (MRI) revealed a mild thickening of the pituitary stalk and lack of hyperintense signal associated with normal neurohypophysis on T1-weighted images. About three months later, the stalk was found to be remarkably expanded like neoplasm; however, anterior pituitary functions were almost normal on that occasion, except for the absence of GH response to an insulin tolerance test. About nine months after the onset of DI, secondary hypoadrenalism and hypothyroidism, which required replacement therapy, developed transiently, but recovered about one year later. Results of hypophysial endocrine tests during this period showed that the dysfunction was predominantly suprapituitary in nature. As time passed, the stalk lesion began to shrink spontaneously and another MRI, obtained five years after the onset of DI, disclosed normal findings for the infundibulo-hypophysial system, except for lack of the hyperintense signal of the neurohypophysis. The patient has since been healthy, except for the DI, which has been controlled by treatment with vasopressin. We report here a unique case of central DI associated with transient pituitary stalk enlargement.

Calcitonin inhibits the growth of human gastric carcinoma cell line KATO III.

Calcitonin has a wide variety of actions on gastrointestinal function. In this study, we investigated the effects of calcitonin on the growth of human gastric carcinoma cell line KATO III in comparison with those of calcitonin gene-related peptide (CGRP). Calcitonin, but not CGRP, significantly and dose-dependently inhibited the growth of KATO III cells. This inhibition of cell growth was accompanied by an increase in cyclic AMP production. The proliferation of KATO III cells was also inhibited by forskolin and dibutyryl cyclic AMP, although agents which do not stimulate cyclic AMP production had no effect. Furthermore, in the presence of GTP, calcitonin stimulated adenylate cyclase activity in KATO III cell membranes, and this increase was reduced in the absence of GTP. On the other had, neither calcitonin nor CGRP enhanced the turnover of inositolphospholipid or the intracellular Ca2+ level. In addition, 125I-labeled human calcitonin was specifically bound to KATO III cell membranes, and this binding was dose-dependently displaced by unlabeled calcitonin but not CGRP. Furthermore, the specific binding of 125I-labeled human calcitonin to KATO III cell membranes was significantly reduced by addition of GTP but not ATP. These results suggest that calcitonin inhibits the growth of human gastric carcinoma cell line KATO III by stimulating cyclic AMP production via a GTP-dependent process coupled to specific calcitonin receptors.

Effects of islet amyloid polypeptide (amylin) and calcitonin gene-related peptide (CGRP) on glucose metabolism in the rat.

In this study, we compared the effects of islet amyloid polypeptide (IAPP) and calcitonin gene-related peptide (CGRP) on glucose metabolism both in vivo and in vitro in the rat. Intravenous injection of rat CGRP caused a significant increase in plasma glucose concentration with a simultaneous increase in plasma insulin levels, whereas neither IAPP-NH2 nor IAPP-COOH had any effect. Moreover, intravenous infusion of CGRP decreased tolerance to intragastric administration of glucose (O-GTT) without altering plasma insulin levels, but again IAPPs had no effect. On the other hand, 125I-[Tyr0]rat CGRP specifically bound to the liver plasma membrane, and not only CGRP but also IAPP-NH2 dose-dependently displaced the specific binding of 125I-[Tyr0] CGRP, whereas IAPP-COOH had no effect. Conversely, CGRP as well as IAPP-NH2 but not IAPP-COOH evoked dose-dependent activation of adenylate cyclase in the membranes, and these effects were significantly inhibited by a CGRP receptor antagonist, human CGRP-I(8-37). However, neither CGRP nor IAPP-NH2 had any effect on glucose production in rat isolated hepatocytes. These results suggest that (1) IAPP-NH2 but not IAPP-COOH induces adenylate cyclase activation via CGRP receptors on rat liver plasma membranes, and (2) CGRP might not involve its action on the liver in the changes of glucose metabolism.

Linkage between capsaicin-stimulated calcitonin gene-related peptide and somatostatin release in rat stomach.

Calcitonin gene-related peptide (CGRP) is present in the stomach, and exogenous CGRP stimulates gastric somatostatin release. A study was undertaken to elucidate the functional linkage between CGRP and somatostatin in the stomach. Newborn Wistar rats were made CGRP deficient by intraperitoneal injection of capsaicin 2 days after birth, and then 2.5 mo later, release of CGRP and somatostatin was examined by vascular perfusion of the isolated stomach. In CGRP-deficient rats, neither the content nor basal secretion of gastric somatostatin differed from that in normal rats, and although none of several secretagogues induced CGRP secretion, the somatostatin response to glucagon was well preserved, indicating the presence of normally functioning D cells. On the other hand, arterial infusion of capsaicin significantly increased the release of not only CGRP but also somatostatin from the stomach of normal rats. In CGRP-deficient rats, however, capsaicin produced no corresponding effect. Finally, human CGRP-(8-37), a CGRP-receptor antagonist, completely inhibited the increase of gastric somatostatin induced by both rat alpha-CGRP and capsaicin infusion in normal rats. Thus the capsaicin-induced increase of somatostatin release appears to be mediated by CGRP in the stomach.

Mechanism of inhibitory action of prostaglandins on the growth of human gastric carcinoma cell line KATO III.

Prostaglandins (PGs) play important roles in the regulation of various gastric functions. In this study, the effects of various PGs on the growth of the human gastric carcinoma cell line KATO III were investigated. All the PGs tested inhibited KATO III cell growth with a relative potency order of PGE2 greater than PGE1 greater than 17S,20-dimethyl-6-oxo PGE1-methyl ester (ornoprostil) greater than PGF2 alpha. This inhibition was accompanied by an increase of cyclic adenosine monophosphate production. Furthermore, in the presence of guanosine triphosphate, these PGs stimulated adenylate cyclase activity in the plasma membrane of KATO III cells, followed by enhancement of membrane guanosine triphosphatase activity. The relative potencies of these PGs for increasing cyclic adenosine monophosphate levels, activating adenylate cyclase, and enhancing guanosine triphosphatase activity were all comparable to those for inhibiting cell growth. On the other hand, the proliferation of KATO III cells was also inhibited by forskolin as well as dibutyryl cyclic adenosine monophosphate, whereas none of the agents that did not increase cyclic adenosine monophosphate levels had any effect. These results suggest that PGs inhibit KATO III cell growth by stimulating cyclic adenosine monophosphate production via a guanosine triphosphate-dependent process, suggesting the involvement of guanosine triphosphate-binding stimulatory protein, probably coupled to PGE2 receptors, in the action of PGs.

Activation of PKC inhibits NaF-induced inositol phospholipid turnover in rat insulinoma cells.

An investigation was done to elucidate the regulatory role of protein kinase C (PKC) in insulin release and also the effects of PKC activation on NaF-induced inositol phospholipid (PI) turnover in and insulin release from rat insulinoma cells (RINr). NaF stimulated insulin secretion in association with an increase in [3H]inositol phosphate formation in RINr cells. Furthermore, NaF induced a rapid decrease in 32P-labeling of phosphatidylinositol-4,5-diphosphate (PIP2) with a concomitant increase of [32P]phosphatidic acid in prelabeled cells. In contrast, NaF had no effect on cyclic AMP production. Although phorbol 12,13-dibutyrate (PDBu) also stimulated insulin release, on concomitant administration of NaF and PDBu, insulin secretion was clearly less than that expected on the basis of an additive action. Moreover, PDBu significantly inhibited NaF-enhanced PI turnover. However, this inhibition was abolished after downregulating PKC by pretreating RINr cells with PDBu. Thus NaF-induced insulin release from RINr cells appears to involve enhancement of PI turnover. Moreover, because NaF is known to activate guanine nucleotide binding proteins (G proteins) directly, PKC activation appears to induce a mechanism that inhibits stimulus-secretion coupling at a level between G protein and phospholipase C-induced PIP2 hydrolysis.

Calcitonin gene-related peptide and induction of hyperglycemia in conscious rats in vivo.

The effect of calcitonin gene-related peptide (CGRP) on glucose metabolism was investigated in conscious and unrestrained rats in vivo. Intravenous injection of rat CGRP (5.67 and 0.567 nmol/kg) caused a significant, dose-dependent increase in plasma glucose concentration and a simultaneous dose-dependent increase in plasma insulin level. In contrast, plasma glucagon level was not changed. On the other hand, intravenous infusion of CGRP (46.6 pmol.kg-1.min-1) decreased tolerance to intragastric administration of glucose (IGGTT). Plasma insulin response to IGGTT, however, was not affected by CGRP infusion. Moreover, although intravenous injection of CGRP (5.67 nmol/kg) elicited a significant increase in plasma epinephrine and norepinephrine concentrations, concomitant administration of epinephrine and norepinephrine, inducing a more prominent rise in plasma catecholamines than those induced by CGRP, affected neither plasma glucose nor insulin levels. Finally, plasma insulin levels obtained by simulating CGRP-induced changes in plasma glucose or glucose plus catecholamine levels by infusion of glucose or glucose plus catecholamines were not different from those induced by CGRP injection. These results suggest that CGRP has a hyperglycemic action that is not mediated by sympathetic outflow in conscious rats, and inhibition of insulin secretion, if any, does not play a major role in this hyperglycemic action of CGRP. We have demonstrated specific CGRP receptors linked to adenylate cyclase activation in rat liver plasma membranes; this hyperglycemic effect of CGRP in vivo may be partly due to its direct action on the liver.

Mechanism for increase of gastrin release by secretin in Zollinger-Ellison syndrome.

In patients with Zollinger-Ellison syndrome, serum gastrin level is increased by secretin and is decreased by somatostatin. To elucidate the cellular mechanism for these actions, we investigated the direct effects of secretin and somatostatin on dispersed gastrinoma cells from a patient with Zollinger-Ellison syndrome. In the presence of 3-isobutyl-1-methylxanthine, secretin significantly stimulated gastrin release from dispersed gastrinoma cells, which was inhibited by somatostatin. In the presence of guanosine 5'-triphosphate, furthermore, secretin enhanced adenylate cyclase activation in the membranes from these cells, and this activation was reduced by somatostatin, whereas neither secretin nor somatostatin affected inositol phospholipid turnover. On the other hand, removal of guanosine 5'-triphosphate from incubation medium abolished both the stimulatory effect of secretin and the inhibitory effect of somatostatin on adenylate cyclase activation. Furthermore, pertussis toxin pretreatment reversed the ability of somatostatin to inhibit secretin-induced increase in gastrin release and activation of adenylate cyclase. Thus, in this gastrinoma patient, secretin and somatostatin appeared to act directly on gastrinoma cells to stimulate and inhibit gastrin secretion, respectively, by modulating adenylate cyclase activation, probably via guanine nucleotide-binding proteins.

Calcitonin gene-related peptide receptor antagonist human CGRP-(8-37).

From this study, we predicted that the human calcitonin gene-related peptide (hCGRP) fragment hCGRP-(8-37) would be a selective antagonist for CGRP receptors but an agonist for calcitonin (CT) receptors. In rat liver plasma membrane, where CGRP receptors predominate and CT appears to act through these receptors, hCGRP-(8-37) dose dependently displaced 125I-[Tyr0]rat CGRP binding. However, hCGRP-(8-37) had no effect on adenylate cyclase activity in liver plasma membrane. Furthermore, hCGRP-(8-37) inhibited adenylate cyclase activation induced not only by hCGRP but also by hCT. On the other hand, in LLC-PK1 cells, where calcitonin receptors are abundant and CGRP appears to act via these receptors, the bindings of 125I-[Tyr0]rat CGRP and 125I-hCT were both inhibited by hCGRP-(8-37). In contrast to liver membranes, interaction of hCGRP-(8-37) with these receptors led to stimulation of adenosine 3',5'-cyclic monophosphate (cAMP) production in LLC-PK1 cells, and moreover, this fragment did not inhibit the increased production of cAMP induced not only by hCT but also by hCGRP. Thus hCGRP-(8-37) appears to be a useful tool for determining whether the action of CGRP as well as that of CT is mediated via specific CGRP receptors or CT receptors.

Prostaglandin E2 and F2 alpha inhibit growth of human gastric carcinoma cell line KATO III with simultaneous stimulation of cyclic AMP production.

The effects of prostaglandins (PGs) on the growth of human gastric carcinoma cell line KATO III were investigated. PGE2 as well as PGF2 alpha significantly and dose-dependently inhibited the growth of this gastric carcinoma cell line (PGE2 greater than PGF2 alpha). This inhibition of cell growth by the PGs was associated with the increase in cyclic AMP production (PGE2 greater than PGF2 alpha), whereas inositol-phospholipid turnover was not affected by either PGE2 or PGF2 alpha as assessed by the formation of 3H-inositol phosphates. Furthermore, the proliferation of these gastric carcinoma cells was also suppressed by the administration of forskolin as well as of dibutyryl cyclic AMP. These results suggest that PGE2 and PGF2 alpha inhibit the growth of cultured human gastric carcinoma cells KATO III via stimulation of cyclic AMP production.

Presence and release of calcitonin gene-related peptide in rat stomach.

Immunoreactive (IR)-calcitonin gene-related peptide (CGRP) was identified throughout the entire stomach of rats, being most highly concentrated in the pyloric region, and the concentrations in muscular layers being higher than those in mucosal layers. In addition, IR-CGRP was also present in the venous effluent from isolated perfused rat stomach, and its release was stimulated by dibutyryl cyclic AMP or theophylline but not by glucagon. Gel chromatography as well as HPLC of both tissue extracts and gastric perfusate showed three identical major peaks of IR-CGRP, one of which coeluted with synthetic CGRP. These results suggest that CGRP in the stomach plays a role in the regulation of gastric function.

Radioimmunoassay of circulating alpha-interferon with reference to aging and osteoporosis.

Circulating immunoreactive alpha-interferon in elderly individuals was 0.139 +/- 0.042 ng/ml in males and 0.111 +/- 0.033 ng/ml in females at ages 70-79, and 0.120 +/- 0.045 ng/ml in males and 0.105 +/- 0.039 ng/ml in females at ages 80-89. These values were significantly lower than those in young adults (p less than 0.01), but higher compared with the values found in disease states including rheumatoid arthritis (p less than 0.0025). There was no correlation between circulating alpha-interferon and bone mass indices, such as bone mineral content or quantitative computed tomography values, in these elderly individuals. Circulating alpha-interferon was, however, significantly increased in senile osteoporotic patients after 2 months of treatment with 1 alpha-hydroxyvitamin D3 or calcitonin, whereas it was unaltered in patients receiving ipriflavone or in nonosteoporotic individuals without medication. These findings indicate that circulating alpha-interferon, which is highest in young adults, declines with aging. It appears that circulating alpha-interferon is maintained at a certain steady-state level in healthy elderly individuals. Although there was no apparent relationship between bone mass indices and circulating alpha-interferon, it is possible that bone and cellular metabolism related to vitamin D3 may be contributing factors for the maintenance of circulating alpha-interferon.

Calcitonin gene-related peptide stimulates adenylate cyclase activation via a guanine nucleotide-dependent process in rat liver plasma membranes.

To evaluate the functional relationship between the liver calcitonin gene-related peptide (CGRP) receptor and guanine nucleotide-binding proteins, we investigated the effects of nucleotides not only on adenylate cyclase activation by CGRP, but also on 125I-[Tyr0]rat CGRP binding to rat liver plasma membranes. In the presence of GTP, rat CGRP stimulated adenylate cyclase activity in a dose-dependent manner in rat liver plasma membranes, and this effect was reduced in the absence of GTP. Salmon calcitonin also enhanced adenylate cyclase activation in the presence of GTP, but only in higher concentrations. On the other hand, guanine nucleotides not only decreased 125I-[Tyr0]rat CGRP binding to rat liver plasma membranes, but also accelerated the dissociation of label binding, and the removal of Mg2+ from incubation medium attenuated this inhibitory action of GTP on 125I-[Tyr0]rat CGRP binding to membranes. Scatchard analysis of the data revealed that the reduction of 125I-[Tyr0]rat CGRP binding by GTP was due to the decrease in binding affinity without a significant change in binding capacity. These findings lead us to conclude that binding of CGRP to its receptors activates adenylate cyclase in rat liver plasma membranes via a guanine nucleotide-dependent process, suggesting the involvement of guanine nucleotide-binding stimulatory protein in the action of CGRP.

Dual action of protein kinase C activation in the regulation of insulin release by muscarinic agonist from rat insulinoma cell line (RINr).

The role of protein kinase C in muscarinic agonist-induced insulin release from rat insulinoma cells was investigated. The dose-dependent stimulation of insulin secretion by carbamylcholine (carbachol) was associated with dose-dependent increase in the release of 3H-inositolphosphates from prelabeled rat insulinoma cell line (RINr) cells. After preincubation with 32P-orthophosphates, carbachol also evoked a rapid decrease in 32P-labeling of phosphatidylinositol-4,5-bisphophate with concomitant increase in 32P-labeling of phosphatidic acid. Furthermore, carbachol significantly increased membrane-associated protein kinase C activity with a simultaneous decrease of its activity in cytosol. Although phorbol-12,13-dibutyrate (PDBu), a protein kinase C activator, also stimulated insulin release, insulin secretion induced by concomitant administration of carbachol and PDBu was clearly less than the level expected on the basis of an additive action. Moreover, PDBu significantly inhibited inositolphospholipid turnover stimulated by carbachol. Finally, PDBu inhibited the binding of 3H-scopolamine binding revealed that PDBu decreased the number of muscarinic receptors without altering its affinity. These findings suggest that activation of protein kinase C not only mediates muscarinic stimulation of insulin secretion from RINr cells but also operates a negative feedback mechanism in a signal transduction system, at least in part, via down-regulation of muscarinic receptors.

Receptors for calcitonin gene-related peptide on the rat liver plasma membranes.

Specific binding sites for calcitonin gene-related peptide (CGRP) were identified in the rat liver plasma membrane. The binding of 125I-[TyrO]rat CGRP to rat liver plasma membrane was time dependent, saturable and reversible. Scatchard analysis of the data revealed a single class of binding sites with apparent dissociation constant of 260.8 pM and a maximal binding capacity of 26.6 fmol/mg of protein. Rat, chick, and human CGRP and their synthetic analogues inhibited label binding in a dose-dependent manner with relative potencies as follows; chick greater than rat greater than human greater than [TyrO]rat CGRP. Salmon, human and [Asu1'7]eel calcitonin also inhibited label binding but only at higher concentrations. These results clearly indicate the presence of specific binding sites for CGRP in rat liver plasma membrane and suggest that CGRP has possible biological actions on the rat liver.

Glucose stimulates insulin release without altering cyclic AMP production or inositolphospholipid turnover in freshly obtained human insulinoma cells.

Glucose, forskolin, IBMX and carbachol all stimulated insulin release from freshly obtained human insulinoma cells. In these same cells, cellular cyclic AMP levels were raised by forskolin and IBMX but not by glucose and carbachol. On the other hand, of all the insulin secretagogues examined, only carbachol stimulated the formation of 3H-inositol trisphosphate in these cells. Thus, in these insulinoma cells, glucose apparently induces insulin secretion without altering cyclic AMP production or inositolphospholipid turnover.

Possible involvement of inositol phosphates and calmodulin in calcitonin-induced stimulation of phosphate transport in LLC-PK1 cells.

The present study investigated the possible involvement of phosphatidylinositol breakdown and Ca2+-calmodulin complex in the calcitonin-induced stimulation of phosphate transport in LLC-PK1 cells. This cell line with calcitonin receptors possesses Na+-dependent phosphate transport and has been employed as a model for studying the mechanism of renal tubular phosphate transport. (Asu1,7) eel calcitonin stimulated the phosphate transport in LLC-PK1 cells in a dose-dependent fashion with accompanying increase of inositol triphosphate (IP3) production. When the cells were preincubated with the potent calmodulin antagonist, w-7 or w-13, the stimulatory effect of calcitonin on phosphate transport was significantly inhibited. These findings indicate that Ca2+-calmodulin complex formed by increased cytosolic Ca2+, which is mobilized from intracellular pools by IP3, may be involved in the signal transduction of calcitonin in these cells.

Effect of 1 alpha (OH)-vitamin D3 on insulin secretion in diabetes mellitus.

Fourteen non-insulin-dependent diabetic subjects were placed on a balanced diet for 2-3 weeks followed by the same balanced diet alone (group I: control, n = 7) or daily administration of 1 alpha (OH)-vitamin D3 (1 alpha (OH)D3) (group II: 2 micrograms/day, n = 7) additionally for the next 3 weeks. A 75 g oral glucose loading test was conducted before and after the experiment and the plasma insulin response was compared along with the metabolic parameters including serum calcium, phosphorus and serum lipids. The following results were obtained. (1) Total insulin secretion in response to 75 g glucose loading was significantly increased in group II (16.3 +/- 3.9 microU/2 h/ml versus 22.7 +/- 4.9 microU/2 h/ml; P less than 0.05), though no difference was demonstrated in group I. (2) Mean serum calcium level was significantly increased from 9.4 +/- 0.1 mg/dl to 9.6 +/- 0.1 mg/dl (P less than 0.05) and serum free fatty acid level was decreased from 0.80 +/- 0.07 mEq/l to 0.53 +/- 0.07 mEq/l (P less than 0.05) in group II, but not in group I. (3) However, there was no direct correlation between total insulin secretion during a 75 g oral glucose loading test and serum calcium or free fatty acid level. The findings that 1 alpha (OH)D3 enhances insulin secretion and reduces the levels of serum free fatty acid in non-insulin-dependent diabetics provide us with the possibility that vitamin D may play some role in the regulation of insulin secretion.

Calcitonin gene-related peptide stimulates somatostatin release from isolated perfused rat stomach.

Effect of calcitonin gene-related peptide (CGRP) on somatostatin release was investigated on the isolated perfused rat stomach. Perfusion with CGRP (0.1 nM-100 nM) caused a significant and dose-dependent increase in effluent somatostatin levels. The somatostatin response to CGRP was rapid in onset and reversible immediately after the cessation of CGRP infusion. These findings suggest that CGRP stimulates the release of gastric somatostatin, thereby modulating gastric functions in rat.

Phorbol esters stimulate phosphate accumulation synergistically with A23187 in cultured renal tubular cells.

The effects of phorbol esters and diacylglycerol on phosphate accumulation in the cultured mouse kidney cells were investigated to assess the possible role of Ca2+-activated, phospholipid dependent protein kinase (protein kinase C) on the renal phosphate handling. 12-O-tetradecanoyl phorbol-13-acetate (TPA) stimulated phosphate accumulation dose-dependently. TPA-induced phosphate accumulation was synergistically enhanced with A23187. 4 alpha-phorbol 12,13-didecanoate did not stimulate the phosphate accumulation, while 4 beta-phorbol 12,13-didecanoate stimulated it. Additionally, 1-oleoyl-2-acetyl-glycerol exhibited a stimulatory effect on phosphate accumulation. These data indicated that protein kinase C is one of possible regulators of phosphate transport at the renal tubules.