The Relationship of the Urotensin-2 Level in the Aqueous Humor with Systemic Diseases and Pupil Size: Comparative Study.

Purpose: To detect the presence of urotensin-2 (U-II) in the aqueous humor and evaluate the relationship between aqueous humor level and systemic diseases and pupil size. Methods: The study included 88 patients who underwent cataract surgery. Those with a pupil diameter (PD) of up to 4 mm were considered to have small dilation, those with 4-7 mm of dilatation were considered to have moderate dilation, and those with a PD of more than 7 mm considered to have large dilation. Patients with HT (hypertension) were classified as group 1, those with DM (diabetes mellitus) as group 2, and those with HT+DM as group 3, and those without any systemic disease as group 4. The U-II levels in humor aqueous samples taken from anterior chamber were measured. Results: When compared with the control group, it was observed that the level of U-II in the aqueous humor of the HT, DM, and DM+HT groups was significantly higher (P < 0.05). At the same time, when we compared the DM+HT group with the other groups, the level of U-II in the aqueous humor was significantly higher compared to the group with DM (P < 0.05). The U-II levels of the aqueous humor were higher in the patients with small pupils compared to the remaining groups (P < 0.005). Conclusion: U-II may play a role in small pupil pathophysiology. In addition, it was determined that patients with HT and/or diabetes had higher U-II levels in the aqueous humor than healthy individuals.

Urotensin 2 and Oxidative Stress Levels in Maternal Serum in Pregnancies Complicated by Intrauterine Growth Restriction.

Background and objectives: In this study, the aim was to investigate Urotensin 2 (U-II) levels and oxidant/antioxidant system parameters in pregnancies with intrauterine growth restriction (IUGR). Materials and Methods: A total of 36 healthy, pregnant women who had not been diagnosed with IUGR and 36 pregnant women who had been diagnosed with IUGR at the Obstetrics and Gynecology Outpatient Clinic at Gaziantep University Hospital were enrolled in this study. The serum total antioxidant status (TAS), total oxidant status (TOS), thiol-disulfide levels, U-II measurements, and oxidative stress index (OSI) calculations were carried out at the biochemistry laboratory at Gaziantep University. Results: According to this study, there was no statistically significant difference between the group with IUGR and the control group of healthy, pregnant women in terms of total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), native thiol, total thiol, disulfide, disulfide/native thiol, disulfide/total thiol, native thiol/total thiol, and U-II values. There was, however, a positive linear correlation between TOS and total thiol levels in the group with IUGR (p = 0.021, r = 0.384), and a positive linear correlation between OSI and total thiol values in the control group (p = 0.049, r = 0.330). In addition, there was a negative correlation between disulfide levels and gestational weeks at birth in the group with IUGR (p = 0.027, r = 0.369). Conclusions: Consequently, there was no significant difference between the control group and the group with pregnancies complicated by idiopathic IUGR in terms of serum oxidant/antioxidant system parameters and U-II levels. It is necessary to conduct more extensive studies evaluating placental, maternal, and fetal oxidative stress in conjunction in order to investigate the role of oxidative stress in IUGR.

Role of Urotensin-2 in 5-Fluorouracil-Related Arterial Vasoconstriction in Cancer Patients.

BACKGROUND: The aim of this study was to identify the possible relationship of 5-fluorouracil (5-FU)-related arterial vasoconstriction with urotensin-2 (UT-2), which has a high potential as an endogenic vasoconstrictor. METHODS: We assigned the patients to 1 of 3 groups. Patients in group 1 received a bolus of 5-FU, those in group 2 a continuous infusion (CI) of 5-FU, and those in group 3 no 5-FU, which was also a control group. Pre- and post-treatment UT-2 levels and brachial arterial diameters were measured and recorded in all patients. RESULTS: 132 patients were included in the study. Pre- and post-treatment brachial artery diameters were similar in all groups: in group 1 (3.28 ± 0.52 vs. 3.25 ± 0.44 mm, p = 0.740), in group 2 (3.57 ± 0.47 vs. 3.46 ± 0.45 mm, p = 0.441) and in the control group (3.51 ± 0.52 vs. 3.25 ± 0.44 mm, p = 0.818). Pre- and post-treatment UT-2 levels were significantly different in each group: in group 1 (39.5 ± 30.9 vs. 56.7 ± 27.1 ng/ml, p = 0.0001), in group 2 (37.7 ± 33.7 vs. 62.5 ± 37.7 ng/ml, p = 0.0001) and in the control group (52.9 ± 40.2 vs. 60.8 ± 40.7 ng/ml, p = 0.006). CONCLUSION: Our findings suggest that UT-2 has a high potential as a vasoconstrictor agent in our bodies and its level increases through a bolus or CI 5-FU. Increased UT-2 levels are likely to play a role in 5-FU-related cardiac toxicity pathogenesis.

An investigation into the expression and mechanism of action of urotensin II in chronic pressure-overloaded rat hearts.

The present study aimed to investigate the role and mode of action of urotensin II (U II) in the occurrence and progression of cardiac fibrosis in a pressure­overload rat model. Coarctation of the abdominal aorta was used to establish an animal model, and postoperative echocardiography, hemodynamic detection, hematoxylin and eosin staining, Masson staining and immunohistochemistry were performed to assess the changes in cardiac function and pathology. The expression levels of U II, G­protein­coupled receptor 14 and collagen (Col) I and Col III in the myocardial tissues were also analyzed. Neonatal rat fibroblasts were isolated, cultured and subsequently, generations 3­5 were randomly divided into different groups for the detection of Col I and Col III levels by enzyme­linked immunosorbent assay and western blotting. The protein expression levels were markedly increased in the model group, and this increase correlated with an increase in myocardial fibrosis. In cultured neonatal rat fibroblast cells, 10­8 mol/l U II significantly stimulated the synthesis of Col I and Col III (P<0.01) compared with the control group. Compared with the U II group, the administration of KT5720 (1 mol/l) or SB­611812 (1 mol/l) significantly reduced the synthesis and expression levels of Col I and Col III (P<0.05). U II may exert an important role in the process of myocardial fibrosis in chronic pressure­overload rats, and the cyclic adenosine monophosphate­protein kinase A signaling pathway may be partly involved in this process.

A comparison of assay performance between the calcium mobilization and the dynamic mass redistribution technologies for the human urotensin receptor.

The popular screening method for urotensin (UT) receptor antagonists is to measure the intracellular calcium concentration with a calcium-sensitive fluorescent dye. This assay format has an inherent limitation on the problem related to the fluorescence interference as it involves fluorescent dyes. In the present study, a label-free assay for the screening of UT receptor antagonists was developed by using dynamic mass redistribution (DMR) assay based on label-free optical biosensor. The addition of urotensin II (UII) stimulated a DMR profile to HEK293 cells stably expressing the human UT receptor (HEK293UT cells) but not on parental cells. The EC50 value of UII in label-free assay was 4.58 nM, which is very similar to that in conventional calcium mobilization assay (4.15 nM). Compared with the calcium mobilization assay for UII (Z' factor, 0.77), the current label-free assay presented improved Z' factor (0.81), with a relatively similar S/B ratio (28.0 and 25.6, respectively). The known high-affinity UT receptor antagonists, SB657510, GSK562590, and urantide, exhibited comparable IC50 values but rather less potent in the DMR assay than in calcium mobilization. Our DMR assay was able to present various functional responses, including inverse agonism in SB657510 and GSK1562590 as well as partial agonism in urantide. Moreover, the DMR assay exerted the stable antagonist window upon the minimal agonist stimulus. These results suggest that the label-free cell-based UT receptor assay can be applicable to evaluate the various functional activities of UT receptor-related drug candidates.

[Changes in urotensin-II expression in airway remodelling in asthmatic rats].

OBJECTIVE: To study the role of urotension-II in serum and bronchoalveolar lavage fluid (BALF) in the process of airway remodelling in asthmatic rats. METHODS: Thirty-two male Sprague-Dawley (SD) rats were randomly divided into normal control and 2-week, 4-week and 8-week asthmatic groups (OVA inhalation of 2, 4 and 8 weeks respectively). Rats were sensitized and challenged by OVA to establish a model of asthma. The bronchial wall thickness and the airway smooth muscle thickness were measured by image analysis system. The urotension-II contents in serum and BALF were determined using ELISA. RESULTS: The bronchial wall thickness and the airway smooth muscle thickness in the three asthmatic groups significantly increased compared with those in the normal control group (P<0.01). The urotension-II contents in serum and BALF in the three asthmatic groups also increased significantly compared with those in the normal control group (P<0.01). The urotension-II contents in serum and BALF in the 8-week asthmatic group were the highest, followed by the 4-week and the 2-week asthmatic groups (P<0.01). BALF urotension-II contents were positively correlated with the bronchial wall thickness and the airway smooth muscle thickness as well as serum U-II contents in the four groups. CONCLUSIONS: The urotension-II contents in serum and BALF in the process of airway remodeling increase in asthmatic rats. The changes in serum and BALF urotension-II contents may be associated with airway remodeling in asthmatic rats.

Renal and vascular actions of urotensin II.

The peptide hormone urotensin II (UII) has been highly conserved through the vertebrates from fish to humans. As it was shown to be the endogenous ligand for the mammalian orphan G-protein-coupled receptor GPR14, now renamed the UT receptor, interest in UII physiology has grown. Initial observations of a potent vasoconstrictor effect have been tempered with the subsequent revelation of an endothelium-dependent vasodilator action. These complex and contrasting vascular actions are both species- and vascular bed-specific. UII also plays a role in body fluid regulation in lower vertebrates, and it now appears that this extends to mammals. The kidney is a major source of both circulating and urinary UII. UII is found in both the proximal tubules and collecting ducts; the UT receptor is localized primarily to the renal medulla, with greatest expression in the inner medullary collecting ducts. Infusion in rats produced conflicting results: exogenous UII has been shown to increase glomerular filtration rate (GFR) and excretion of water and sodium, but also to reduce the same variables. Inhibition of UT receptor activity with the antagonist urantide resulted in an increase in GFR, diuresis, and natriuresis, suggesting that endogenous UII exerts a tonic influence on basal renal function. UII may also play a role in renal disease, being elevated in the circulation or urine of patients with renal failure and in experimental models of cardiovascular disease such as the spontaneously hypertensive rat. It remains to be established whether these changes represent an underlying primary cause or a compensatory response.

Effects of pre-eclampsia on maternal plasma, cerebrospinal fluid, and umbilical cord urotensin II concentrations: a pilot study.

BACKGROUND: Urotensin II (UII) is the most potent endogenous vasoconstrictor identified to date. Pre-eclampsia is associated with arteriolar vasospasm but the precise underlying mechanism is uncertain and we hypothesized that UII concentrations might also be elevated. In this study we measured UII concentrations in maternal plasma and cerebrospinal fluid (CSF), and umbilical vein plasma from pre-eclamptic (PET) and normotensive patients undergoing elective Caesarean section under spinal or combined spinal-epidural anaesthesia. METHODS: With LREC approval and informed consent we recruited two groups of 10 patients; control [mean (range) age, 29 (22-43) yr; BMI, 25 (20-32); gestation, 273 (267-281) days; mean arterial pressure (MAP) on day of delivery, 81 (75-96) mm Hg] and PET [age, 34 (22-40) yr; BMI, 25 (21-46); gestation, 253 (203-289) days; MAP on day of delivery, 106 (88-128) mm Hg]. Maternal blood and CSF samples and umbilical vein blood samples were taken. UII was extracted and concentrations measured using a radioimmunoassay. RESULTS: Two plasma and two CSF samples in the control and two CSF samples in the PET group were below the assay detection limits. There were no differences in maternal plasma or CSF or umbilical vein UII concentrations between the groups. However, there was a small ( approximately 40%) but significant increase in cord UII concentrations when compared with paired plasma in the PET group. There was a weak but significant negative correlation (r=-0.4, P=0.049) between cord UII concentrations and gestation in the PET group. In addition, we observed a significant positive correlation between plasma and CSF (r(2)=+0.57, P=0.0009, n=16), plasma and cord (r(2)=+0.43, P=0.0031, n=18) and CSF and cord (r(2)=+0.32, P=0.022, n=16) UII concentrations for the whole data set. CONCLUSIONS: Collectively the data indicate that UII concentrations do not increase in PET compared with controls but, in PET patients, cord UII concentrations are elevated relative to paired plasma samples. Elevated umbilical vein UII concentrations may simply indicate reduced placental viability and possibly UII metabolism as a result of reduced blood flow or possibly that the placenta is producing UII.

Differential levels of "urotensin-II-like" activity determined by radio-receptor and radioimmuno-assays.

Plasma and urinary levels of "urotensin(U)-II-like" substances determined in healthy human volunteers were 12.4 +/- 0.6 ng/ml and 2.2 +/- 0.3 ng/ml by RIA, an order of magnitude lower than that seen by RRA, 167.5 +/- 9.5 ng/ml and 65.2 +/- 4.3 ng/ml. HPLC demonstrated the existence of at least three prominent activity peaks in plasma and urine, the more hydrophobic of which did not co-elute with U-II, degradation products or URP. RRA and RIA recognized these peaks with contrasting efficacy. As such, published levels of "U-II-like" activity should be interpreted with caution until a better understanding is obtained regarding what species specific RIA and RRA assay reagents interact with.

Biochemical characterization and immunohistochemical localization of urotensin II in the human brainstem and spinal cord.

The human urotensin II (UII) precursor encompasses several potential cleavage sites and thus, processing of pro-UII may generate various forms of mature UII including the peptides of 11 (UII11), 16 (UII16) and 19 (UII19) residues. Until now, the native form of human UII had not been characterized. Here, we show that the major UII peptide occurring in the human spinal cord corresponds to UII11. In contrast, neither the UII16 nor the UII19 forms could be detected. In 50% of the brainstem and in all the spinal cord extracts analysed, a second minor UII-immunoreactive peptide was resolved. Immunohistochemical labelling of the cervical segment of the human spinal cord revealed that the UII-immunoreactive material was confined to a subset of ventral horn motoneurones. These data provide the first evidence that in the human, the UII precursor, expressed in motoneurones, is processed at the tribasic KKR93 cleavage site to generate a mature form of UII of 11 amino acids. The absence of N-terminally elongated forms of UII of 16 and 19 residues indicates that pro-UII is not cleaved at the R85 or K88 monobasic sites. Finally, the minor UII-immunoreactive peptide detected in several tissue extracts might correspond to an extended form of UII resulting from the processing of the UII precursor at the basic RK50 or RK66 doublets.

[Expression of urotensinII in human coronary artery and coronary atherosclerosis].

OBJECTIVE: To assess the expression intensity of urotensinII (UII) in normal and atheromatous human coronary artery and explore its significance in coronary atherosclerosis. METHODS: Specimens of coronary arteries were obtained from 5 normal subjects and the expression of human UII in the specimens was detected by immunohistochemical method. RESULTS: UII expression was found in the endothelial cells (ECs), foam cells (FCs), inflammatory cells (ICs) and intima smooth muscle cells (ISMs) of human coronary artery. Even in the normal coronary artery, UII expression could be detected immunohistochemically in the ECs, which, however, was characterized by higher UII expression levels in fatty streak lesions but by almost normal levels in fibrous and atheromatous plaque in the coronary artery. Enhanced UII expression was observed in FCs and ICs when fibrous plaque and atheromatous plaque developed in comparison with that in fatty streak lesions. The ISMs in all the lesions had mild UII immunoreactivity, but as the atherosclerosis exacerbated, the immunoreactivity tended to intensify. CONCLUSION: Human UII may regulate the functions of ECs, FCs, ICs and ISMs in the development and progression of coronary atherosclerosis.

Three vasoactive peptides, endothelin-1, adrenomedullin and urotensin-II, in human tumour cell lines of different origin: expression and effects on proliferation.

Evidence has accumulated showing that vasoactive peptides, such as endothelin-1, adrenomedullin and urotensin-II, are expressed in various kinds of tumour cells. In the present study, the expression of endothelin-1 and endothelin receptors was studied in eight human tumour cell lines: T98G (glioblastoma), IMR-32 and NB69 (neuroblastoma), BeWo (choriocarcinoma), SW-13 (adrenocortical carcinoma), DLD-1 (colonic carcinoma), HeLa (cervical carcinoma) and VMRC-RCW (renal carcinoma). Reverse transcriptase-PCR showed expression of endothelin-1 mRNA in seven out of the eight cell lines, the exception being BeWo cells. ET(A) receptor mRNA was expressed in T98G, IMR-32 and NB69 cells, but weakly in the other cells. ET(B) receptor mRNA was expressed in IMR-32, NB69 and BeWo cells, but only weakly in T98G and HeLa cells. Immunoreactive endothelin was detected in the culture media of six out of the eight cell lines, but not in that of IMR-32 or BeWo cells. Treatment of T98G cells with an anti-endothelin-1 antibody or an anti-adrenomedullin antibody for 24 h decreased cell numbers to approx. 84% and 90% of control respectively. Treatment with the ET(A) receptor antagonist BQ-610 (1 microM) significantly decreased cell number to about 90% of control, whereas the ET(B) receptor antagonist BQ-788 had no significant effect. On the other hand, exogenously added endothelin-1, adrenomedullin or urotensin-II (0.1 microM) had no significant effects on cell number. These results suggest that endothelin-1 acts as a paracrine or autocrine growth stimulator in tumours. The effect of endothelin-1 on tumour growth appears to be mediated by the ET(A) receptor.

A homologous radioimmunoassay for the measurement of urotensin II in the euryhaline flounder, Platichthys flesus.

A sensitive and specific homologous radioimmunoassay (RIA) has been developed to measure tissue and circulating levels of the fish caudal neurosecretory system neuropeptide, urotensin II (UII), in the euryhaline flounder Platichthys flesus. A polyclonal antiserum was raised against flounder UII in rabbit; UII-125I was produced by the iodogen method and purified by HPLC. Antiserum specificity to flounder UII was demonstrated through lack of cross-reactivity with several small peptides and parallelism with standard curves for serial dilutions of UII in plasma and urophysial extracts. Biological activity of the peptide measured by UII RIA was confirmed by bioassay. Plasma intra- and interassay coefficients of variation were 9 and 18% (n = 5 and n = 3), respectively, nonspecific binding constituted 4.6% (+/-1.42%, n = 8) of total counts, and the limit of RIA detectability was estimated as 1.5 x 10(-16) M UII/assay tube. Plasma samples were subject to a reversed-phase liquid chromatography purification protocol which had an extraction efficiency of 63% (+/-10%, n = 6) and showed consistent recovery of UII over a range of plasma volumes and peptide concentrations. Plasma UII concentrations in seawater (SW)-adapted flounder (3.80 +/- 0.77 x 10(-11) M, n = 7) were significantly higher than those in freshwater (FW)-adapted fish (1.10 +/- 0.15 x 10(-11) M, n = 7). This variation coincided with differences in plasma osmolality and Na+ levels. No differences were found, however, between urophysial UII concentrations in SW-adapted (3.71 +/- 1.78 x 10(-10) M UII/gland, n = 7) and FW-adapted (2.53 +/- 1.33 x 10(-10) M UII/gland, n = 7) flounder.

The caudal neurosecretory system and its afferent synapses in the goldfish, Carassius auratus: morphology, immunohistochemistry, and fine structure.

Morphological features of the goldfish caudal neurosecretory system were investigated by means of immunohistochemical localization of urotensins I and II (UI and UII) and electron microscopic examination of the caudal neurosecretory neurons, the urophysis, and the synaptic neuropil. The aim of the work is to provide a detailed morphological description of the afferent synapses to the caudal neurons and to analyze their distribution through the rostrocaudal extension of the caudal neurosecretory system. Three morphologically different types of neurosecretory cells have been identified according to size and shape: large, medium, and small Dahlgren cells. The three different-sized cells share similar patterns of immunoreactivity with the UI (or oCRF) and the UII antisera. Electron microscopic examination of the synaptic neuropil throughout the caudal system revealed the presence of four types of terminals: dense-cored-vesicle end bulbs (DC), spherical-vesicle end bulbs (S), flattened-vesicle end bulbs (F), and granular-vesicle end bulbs (G). The present study demonstrates that the small Dahlgren cells receive different synaptic inputs from the large and the medium neurosecretory cells. Indeed, G terminals are only found on the small Dahlgren cells, whereas DC, S, and F terminals are distributed on the large, medium, and small Dahlgren cell bodies and proximal processes.

Urotensin II in the central nervous system of the frog Rana ridibunda: immunohistochemical localization and biochemical characterization.

Urotensin II (UII) is traditionally regarded as a product of the neurosecretory cells in the caudal portion of the spinal cord of jawed fishes. A peptide related to UII has been recently isolated from the frog brain, thereby providing the first evidence that UII is also present in the central nervous system of a tetrapod. In the present study, we have investigated the distribution of UII-immunoreactive elements in the brain and spinal cord of the frog Rana ridibunda by immunofluorescence using an antiserum directed against the conserved cyclic region of the peptide. Two distinct populations of UII-immunoreactive perikarya were visualized. The first group of positive neurons was found in the nucleus hypoglossus of the medulla oblongata, which controls two striated muscles of the tongue. The second population of immunoreactive cell bodies was represented by a subset of motoneurons that were particularly abundant in the caudal region of the cord (34% of the motoneuron population). The telencephalon, diencephalon, mesencephalon, and metencephalon were totally devoid of UII-containing cell bodies but displayed dense networks of UII-immunoreactive fibers, notably in the thalamus, the tectum, the tegmentum, and the granular layer of the cerebellum. In addition, a dense bundle of long varicose processes projecting rostrocaudally was observed coursing along the ventral surface of the brain from the midtelencephalon to the medulla oblongata. Reversed-phase high-performance liquid chromatography analysis of frog brain, medulla oblongata, and spinal cord extracts revealed that, in all three regions, UII-immunoreactive material eluted as a single peak which exhibited the same retention time as synthetic frog UII. Taken together, these data indicate that UII, in addition to its neuroendocrine functions in fish, is a potential regulatory peptide in the central nervous system of amphibians.

Presence of sauvagine-like epitopes in the interrenal gland of the bullfrog Rana catesbeiana.

Immunocytochemistry was used to investigate the presence of corticotropin-releasing factor-like peptides in the interrenal (adrenal) glands of the bullfrog Rana catesbeiana by using specific antisera raised against synthetic nonconjugated rat/human corticotropin-releasing factor, urotensin I, and sauvagine. From these three antisera, covering a broad range of corticotropin-releasing factor-like immunoreactivities, only the sauvagine antiserum gave positive immunoreactivity. Sauvagine immunoreactivity was found in cortical cells grouped into cords in the renal zone of the interrenal gland. The central and subcapsular cords were less stained. Tyrosine hydroxylase-positive chromaffin cells were not sauvagine-immunoreactive. The immunoreactivity was abolished, in all cases, by previous immunoabsorption of the sauvagine antiserum with synthetic sauvagine (0.1 microM), but it was not eliminated by sucker (Catostomus commersoni) urotensin I, sole (Hippoglossoides elassodon) urotensin I, sucker corticotropin-releasing factor, rat/human corticotropin-releasing factor, or ovine corticotropin-releasing factor (0.1-10 microM). In a sauvagine radioimmunoassay, interrenal extracts displaced 125I-sauvagine from antiserum only partially, and not in parallel with the sauvagine standard curve. The results suggest that the sauvagine immunoreactivity in the R. catesbeiana interrenal gland may represent a novel sauvagine-like peptide.

Immunohistological localization of regulatory peptides in the midgut of the female mosquito Aedes aegypti.

The midgut of the female mosquito Aedes aegypti was studied immunohistologically with antisera to various regulatory peptides. Endocrine cells immunoreactive with antisera to perisulfakinin, RFamide, bovine pancreatic polypeptide, urotensin 1, locustatachykinin 2 and allatostatins A1 and B2 were found in the midgut. Perisulfakinin, RFamide and bovine pancreatic polypeptide all react with the same, about 500 endocrine cells, which were evenly distributed throughout the posterior midgut, with the exception of its most frontal and caudal regions. In addition, these antisera recognized three to five neurons in each ingluvial ganglion and their axons, which ran longitudinally over the anterior midgut, as well as axons innervating the pyloric sphincter. The latter axons appear to be derived from neurons located in the abdominal ganglia. Antisera to two different allatostatins recognized about 70 endocrine cells in the most caudal area of the posterior midgut and axons in the anterior midgut whose cell bodies were probably located in either the brain or the frontal ganglion. Antiserum to locustatachykinin 2 recognized endocrine cells present in the anterior midgut and the most frontal part of the posterior midgut, as well as about 50 cells in the most caudal region of the posterior midgut. Urotensin 1 immunoreactivity was found in endocrine cells in the same region as the perisulfakinin-immunoreactive cells, but no urotensin-immunoreactive axons were found in the midgut. Double labeling experiments showed that the urotensin and perisulfakinin immunoreactivities were located in different cells. Such experiments also showed that the locustatachykinin and allatostatin immunoreactivities in the most caudal area of the posterior midgut were present in different cells. No immunoreactivity was found in the mosquito midgut when using antisera to corazonin, allatropin or leucokinin IV. Since these peptides have either been isolated from, or can reasonably be expected to be present in mosquitoes, it was concluded that these peptides are not present in the mosquito midgut.