Large Congenital Cutaneous Mastocytoma Presenting With Recurrent Persistent Blistering: A Case Report

Congenital cutaneous mastocytoma is an uncommon disorder characterized by abnormal proliferation of mast cells. It typically presents as a single, small, yellowish-brown plaque, and its diagnosis is generally facilitated by distinctive clinical features, including a positive Darrier's sign. This report presents a case of an unusually large, solitary congenital mastocytoma encompassing nearly the entire circumference of the calf, observed in a newborn boy of Bangladeshi origin. Measuring 13x6 cm, the lesion formed large bullae and subsequent erosions. The perplexing clinical appearance prompted a skin biopsy, revealing monomorphic CD117 (c-KIT) positive infiltration without significant cell pleomorphism, confirming the diagnosis of cutaneous mastocytoma. The patient underwent management with potent and very potent topical steroids, oral antihistamines, and non-adhesive dressings, remaining under long-term follow-up with secondary care dermatology. In reporting this case, our objective is to augment the existing scientific literature by providing additional evidence that cutaneous mastocytomas can display a spectrum of clinical presentations, as illustrated in this case.

Erythema multiforme-like lesions in a patient with systemic lupus erythematosus progressing to toxic epidermal necrolysis-like lupus

A 34-year-old woman of African ancestry had a diagnosis of systemic lupus erythematosus that was antinuclear antibodies (> 1 : 640, speckled), anti-U1-ribonucleoprotein, anti-Smith and anti-C1q positive. She presented to hospital with severely painful annular and polycyclic erosions, some with a targetoid-like appearance. After 6 weeks she developed slowly evolving dusky papules/plaques and flaccid bullae, suggestive of toxic epidermal necrolysis-like lupus, and was successfully treated with intravenous rituximab and intravenous immunoglobulin (2 g kg–1 over 3 days).

The reorganisation of emergency general surgery services during the COVID-19 pandemic in the UK: outcomes of delayed presentation, socio-economic deprivation and Black, Asian and Minority Ethnic patients

INTRODUCTION

The COVID-19 pandemic is a global public health emergency. Lockdown restrictions and the reconfiguration of healthcare systems to accommodate an increase in critical care capacity have had an impact on 'non-COVID' specialties. This study characterises the utilisation of emergency general surgery (EGS) services during the UK lockdown period at a university teaching hospital with a catchment population that represents one of the most deprived and ethnically diverse areas in the UK.

METHODS

EGS admissions during the UK lockdown period (March to May 2020) were compared with the same period in 2019. Patient demographics were recorded together with clinical presentation, hospital stay and treatment outcomes, and readmission data.

RESULTS

The study included 645 patients, comprising 223 in the COVID-19 period and 422 in the non-COVID-19 period. There was no difference in age, sex, comorbidity or socio-economic status. A lower proportion of patients of Black, Asian and Minority Ethnicity (BAME) were admitted during the pandemic (20.6% vs 35.4%, p < 0.05). The duration of symptoms prior to presentation was longer, and admission clinical parameters and serum inflammatory markers. More patients presented with an acute kidney injury (9.9% vs 4.7%, p = 0.012). There was no difference in perioperative outcomes or 30-day mortality, but more patients were readmitted following conservative management (10.6% vs 4.7%, p = 0.023).

CONCLUSIONS

The reorganisation of EGS to a senior-led model has been successful in terms of outcomes and access to treatment despite a more unwell population. There was a significantly lower proportion of BAME admissions suggesting additional barriers to healthcare access under pandemic lockdown conditions.

Congenital diaphragmatic hernia causing cardiac arrest in a 30-year-old woman

Congenital diaphragmatic hernia (CDH) usually presents in infancy with respiratory failure requiring urgent surgical correction. Mortality in this group of patients remains poor and persistent pulmonary hypertension is a significant contributor. It is therefore rare for patients to reach adulthood undiagnosed. CDH is often identified incidentally in adults but when symptoms arise, they relate to the organ involved, and include gastrointestinal symptoms of dyspepsia and obstruction, as well as respiratory complaints such as dyspnoea. We present the case of a 30-year-old woman who was admitted with non-specific symptoms of upper abdominal discomfort but whose deteriorating condition culminated in a cardiac arrest, as an unreported presentation of CDH. The patient presented initially with severe left upper quadrant pain. Her chest x-ray on admission suggested a raised left hemidiaphragm. She went on to have computed tomography (CT) of the thorax and abdomen as well as oesophagogastroduodenoscopy, which raised the suspicion of diaphragmatic eventration. Repeat CT was performed after the patient collapsed on the ward five days following admission, revealing tracheal deviation, and a strangulated Bochdalek hernia containing stomach and spleen. After transfer to the anaesthetic room, she suffered a cardiac arrest. Advanced life support was required to return spontaneous cardiac function. She was intubated and ventilated, and a needle thoracostomy was performed to decompress the tension gastrothorax. Emergency laparotomy revealed a gangrenous stomach and spleen. Total gastrectomy with primary Roux-en-Y reconstruction, splenectomy and insertion of a feeding jejunostomy were performed. The patient recovered well postoperatively and was discharged two weeks following surgery.

Target and nontarget effects of novel "triple-stacked" Bt-transgenic cotton 1: canopy arthropod communities

Transgenic cotton varieties (Bollgard II) expressing two proteins (Cry1Ac and Cry2Ab) from Bacillus thuringiensis (Bt) have been widely adopted in Australia to control larvae of Helicoverpa. A triple-stacked Bt-transgenic cotton producing Cry1Ac, Cry2Ab, and Vip3A proteins (Genuity Bollgard III) is being developed to reduce the chance that Helicoverpa will develop resistance to the Bt proteins. Before its introduction, nontarget effects on the agro-ecosystem need to be evaluated under field conditions. By using beatsheet and suction sampling methods, we compared the invertebrate communities of unsprayed non-Bt-cotton, Bollgard II, and Bollgard III in five experiments across three sites in Australia. We found significant differences between invertebrate communities of non-Bt and Bt (Bollgard II and Bollgard III) cotton only in experiments where lepidopteran larval abundance was high. In beatsheet samples where lepidopterans were absent (Bt crops), organisms associated with flowers and bolls in Bt-cotton were more abundant. In suction samples, where Lepidoptera were present (i.e., in non-Bt-cotton), organisms associated with damaged plant tissue and frass were more common. Hence in our study, Bt- and non-Bt-cotton communities only differed when sufficient lepidopteran larvae were present to exert both direct and indirect effects on species assemblages. There was no overall significant difference between Bollgard II and III communities, despite the addition of the Vip gene in Bollgard III. Consequently, the use of Bollgard III in Australian cotton provides additional protection against the development of resistance by Helicoverpa to Bt toxins, while having no additional effect on cotton invertebrate communities.

Characterization of Δ7/11, a functional prolactin-binding protein

Prolactin is essential for normal mammary gland development and differentiation, and has been shown to promote tumor cell proliferation and chemotherapeutic resistance. Soluble isoforms of the prolactin receptor (PrlR) have been reported to regulate prolactin bioavailability by functioning as 'prolactin-binding proteins'. Included in this category is Δ7/11, a product of alternate splicing of the PrlR primary transcript. However, the direct interactions of prolactin with Δ7/11, and the resulting effect on cell behavior, have not been investigated. Herein, we demonstrate the ability of Δ7/11 to bind prolactin using a novel proximity ligation assay and traditional immunoprecipitation techniques. Biochemical analyses demonstrated that Δ7/11 was heavily glycosylated, similar to the extracellular domain of the primary PrlR, and that glycosylation regulated the cellular localization and secretion of Δ7/11. Low levels of Δ7/11 were detected in serum samples of healthy volunteers, but were undetectable in human milk samples. Expression of Δ7/11 was also detected in six of the 62 primary breast tumor biopsies analyzed; however, no correlation was found with Δ7/11 expression and tumor histotype or other patient demographics. Functional analysis demonstrated the ability of Δ7/11 to inhibit prolactin-induced cell proliferation as well as alter prolactin-induced rescue of cell cycle arrest/early senescence events in breast epithelial cells. Collectively, these data demonstrate that Δ7/11 is a novel regulatory mechanism of prolactin bioavailability and signaling.

Hydride spectroscopy of the diffuse interstellar medium: new clues on the gas fraction in molecular form and cosmic ray ionization rate in relation to H3+

The Herschel-guaranteed time key programme PRobing InterStellar Molecules with Absorption line Studies (PRISMAS)(1) is providing a survey of the interstellar hydrides containing the elements C, O, N, F and Cl. As the building blocks of interstellar molecules, hydrides provide key information on their formation pathways. They can also be used as tracers of important physical and chemical properties of the interstellar gas that are difficult to measure otherwise. This paper presents an analysis of two sight-lines investigated by the PRISMAS project, towards the star-forming regions W49N and W51. By combining the information extracted from the detected spectral lines, we present an analysis of the physical properties of the diffuse interstellar gas, including the electron abundance, the fraction of gas in molecular form, and constraints on the cosmic ray ionization rate and the gas density.

Rationalized polytherapy for epilepsy

In the past, epilepsy was usually treated with polytherapy, but with little knowledge as to the interactions and side-effects of the combinations of the anti-epileptic drugs used. Adverse events and sparse clinical knowledge led to monotherapy becoming the treatment regime of choice. A new generation of drugs, which are well-tolerated and have few or predictable interactions, have enabled the reassessment of polytherapy for the treatment of epilepsy. Extensive clinical trials of these drugs are allowing the emergence of a new, rationalized approach to polytherapy. In our study, 19 patients with refractory partial epilepsy, and who were 'socially active and integrated into society', received vigabatrin as add-on therapy. Patients were taking a mean of 1.5 drugs, and five patients were taking small doses of drugs which lead to tolerance, such as barbiturates and benzodiazepines. With vigabatrin as add-on therapy, 14 patients (73%) had a greater than 50% reduction in seizure frequency, and 10 (52%) had a greater than 70% reduction in seizure frequency. In one patient, seizure frequency increased, and two patients developed myoclonic jerks. Vigabatrin was not shown to have any harmful effects in extensive laboratory, EEG and cognitive function tests. In fact, a minor improvement occurred in visual memory, which was probably related to the reduction in seizures. Addition of vigabatrin may, therefore, be of benefit to patients with partial epilepsy refractory to monotherapy with standard anti-epilepsy drugs.

Methods to enhance the safety of methotrexate prescribing

The treatment of chronic inflammatory conditions often involves a difficult balance between the benefits of disease modification and the risks attendant with the use of disease-modifying agents. Methotrexate is a useful and commonly used disease-modifying agent but has a particularly notable reputation for causing morbidity and mortality. We explore ways in which the safety of methotrexate prescribing may be improved. There has been considerable debate as to the whether some of the side-effects can be mitigated by co-prescription of folate with methotrexate. Whereas no definitive conclusion can yet be reached, evidence suggests that the improvement in side-effect profile is limited to fewer elevations of liver enzymes, but that this may be at the expense of decreased methotrexate efficacy. The question remains as to whether the improved tolerability more than compensates for the decreased efficacy or whether folic acid should be used in a more circumspect way. However, a very specific danger arises from the fact that methotrexate is prescribed once weekly for inflammatory conditions, leading to errors at both the prescription and patient level. We highlight simple ways of improving safety to decrease such errors.

An osteopontin fragment is essential for tumor cell invasion in hepatocellular carcinoma

Tumor cell invasion is a primary event in the metastatic progression of hepatocellular carcinoma (HCC). Our recent results indicate a concordant elevated expression of osteopontin (OPN) and matrix metalloproteinase-9 (MMP-9) in primary metastatic HCC. This study hypothesizes an MMP-9-directed cleavage of OPN that biologically contributes to HCC metastasis. We found that MMP-9 cleaved OPN into specific fragments in vitro, of which three could be identified by Edman degradation amino-acid sequencing. One of these fragments (OPN-5 kDa, residues 167-210) induced low-metastatic HCC cellular invasion via CD44 receptors, which was effectively blocked by the addition of small peptides within the region of OPN-5 kDa. Increased expression of an OPN splice variant (OPN-c) was associated with clinical metastatic HCC. Overexpression of OPN-c with physiological levels of MMP-9 enhanced cellular invasion and coincided with elevated OPN-5 kDa levels. Our data suggest that an alternative splicing event (OPN-c) promotes extracellular cleavage of OPN by MMP-9, thus releasing a distinct region of OPN (OPN-5 kDa) that is essential for HCC cellular invasion and appears to correlate with metastatic potential. The findings of this study may help to improve advanced-stage HCC prognosis and suggest the utility of small peptides for novel therapies.

Systemic pyoderma gangrenosum responding to infliximab and adalimumab

Pyoderma gangrenosum (PG) is frequently associated with constitutional symptoms as part of a nonspecific inflammatory response. However, extracutaneous discrete aseptic neutrophilic infiltrates are extremely rare. We report a patient with idiopathic PG with splenic and psoas muscle involvement. His disease was extremely aggressive and was unresponsive to conventional immunosuppressive therapy. His cutaneous and extracutaneous PG cleared with infliximab and adalimumab.

The zebrafish as a tool for understanding the biology of visual disorders

Retinal degenerations are the commonest cause of blindness in the Western world, affecting 5% of the population, yet remain largely untreatable. A better understanding of the mechanisms of disease is needed. Zebrafish fill a gap in the current repertoire of models, offering genetic tractability in a vertebrate. Their retina has many similarities with a human retina. Importantly, unlike rodents, they have rich colour vision, offering the potential to model the macular degenerations. A variety of physiological assays, genetic manipulations and histological tools have been developed and useful models of human disease created.

Optimizing pasture management for cow-calf production: the roles of rotational frequency and stocking rate in the context of system efficiency

An experiment was conducted on grass pasture in southwestern Quebec to evaluate the benefits of management intensive grazing (MiG). Sixty-one spring-calving cows, with calves, were assigned to nine treatments, arranged as a 3 x 3 factorial of rotational frequency (RF) (high, 2-d; medium, 6-d; continuous grazing) and stocking rate (SR) ( high, medium and low; 0.5, 0.7 and 0.9 ha per cow-calf pair, respectively). Hay harvested early in the season was used for pasture supplementation late in the season. Increasing RF had no effect (P > 0.05) on mean forage mass. Increasing SR from 0.9 to 0.5 ha per cow-calf pair resulted in a linear reduction (P < 0.01) in mean forage crude protein (CP) in September; forage CP was highest with 6-d rotation. At the start of the season, increasing RF caused a linear decrease (P < 0.01) in cow gain per head as well as gain per hectare, whereas increasing the SR caused a linear increase (P < 0.01) in cow gain per hectare without influencing cow gain per head (P > 0.05). Calf gain per hectare increased linearly (P < 0.01) in response to SR throughout the grazing season, but calf gain per head was unaffected (P > 0.05) by SR. Calf gains per head and per hectare were not influenced by RF until late season, when calves under a 6-d RF performed slightly better than both continuously grazed and 2-d RF calves. A 6-d-high SR system generated the greatest net revenue. The study showed little benefit of MiG on animal performance, but substantial benefit on efficiency of land use and economic performance. Key words: Grazing, cow-calf, net revenue, economics, animal performance

Evaluating a telemedicine system to assist in the management of dermatology referrals

BACKGROUND

Teledermatology systems fall into two categories: live video or store-and-forward. In the former, video-conferencing equipment is used to connect a patient with a remote consultant. This method has been evaluated as an aid to dermatology, but it is expensive both in terms of capital and running costs. Video consultations are generally longer than conventional ones and harder to schedule. Some authors have considered store-and-forward as an alternative to live video: instead of a consultation, specialists could make a rapid inspection of a transmitted still image.

OBJECTIVES

A study was conducted to evaluate the role of telemedicine in the dermatology outpatients department of a district general hospital (Whittington Hospital NHS Trust, London, U.K.).

METHODS

One hundred and ninety-four patients were seen by one of two consultant dermatologists. A nurse used a video camera to store digital images of each patient's problem and compiled a history from the GP's referral letter. The images were reviewed 13 months later by both dermatologists; they recorded a provisional diagnosis and an assessment of how urgent an appointment would have been made given the information provided by the system. A third consultant graded the level of agreement between the telemedicine diagnoses and the face-to-face consultations.

RESULTS

High levels of agreement were found between the diagnoses of the dermatologists using the system to inspect images and those of the dermatologist who saw the patients (77%). Consultants using the system recommended fewer urgent appointments (32% compared with 64%) and felt that in 31% of cases the patient did not need to be seen. In 15% of these cases (5% of the total), however, their diagnosis differed significantly from that of the consultant who saw the patient. Had the system been in use, 14% of patients conventionally assigned a non-urgent appointment would have been seen urgently.

CONCLUSIONS

The images allowed a reasonably accurate diagnosis. The software was not reliable (six cases could not be viewed), or easy to use (it took approximately an hour to view 20 cases) but an improved version could be used in triaging outpatient appointments.

Surface membrane biotinylation efficiently mediates the endocytosis of avidin bioconjugates into nucleated cells

Here we demonstrate that biotin covalently attached to cell surface obligates existing receptors to endocytose avidin bioconjugates into nucleated cells. Incubation of fluorescein-labeled avidin with biotinylated cell lines resulted in uniform and rapid surface attachment and endocytosis compared with no detectable association of the avidin-conjugated dye with unbiotinylated cells. Uptake was detected within minutes with efficiencies approaching 100% in cell lines and freshly obtained peripheral blood mononuclear cells. After 24 h, avidin was barely detectable on the surface of the nucleated cells. In marked contrast, fluorescent avidin remained exclusively on the external membrane of erythrocytes after 24 h. To investigate biotin-mediated endocytosis for the delivery of DNA, we prepared polyethylenimine-avidin (PEI-avidin) conjugates. Surface biotinylation significantly increased the transfection efficiencies of PEI-avidin condensed plasmid DNA coding green fluorescent protein (GFP) to the level of transferrin-receptor targeted gene delivery (15-20% GFP positive cells in culture after 48 h). The increase in transfection efficiency was blocked by the addition of free avidin or biotin to the culture medium. Biotin covalently bound to cell surface membrane proteins efficiently mediates the entry of avidin bioconjugates into nucleated cells.

Extrinsic cerebral venous sinus obstruction resulting in intracranial hypertension

We report the case of a 70-year-old man reporting with headache and visual disturbances who was being treated for prostate cancer. Investigations showed him to have intracranial hypertension caused by venous sinus obstruction. Patients with metastatic disease and raised intracranial pressure in the absence of focal signs should be considered as possible cases of venous outflow obstruction.

Follicular thyroglobulin (TG) suppression of thyroid-restricted genes involves the apical membrane asialoglycoprotein receptor and TG phosphorylation

Follicular thyroglobulin (TG) decreases expression of the thyroid-restricted transcription factors, thyroid transcription factor (TTF)-1, TTF-2, and Pax-8, thereby suppressing expression of the sodium iodide symporter, thyroid peroxidase, TG, and thyrotropin receptor genes (Suzuki, K., Lavaroni, S., Mori, A., Ohta, M., Saito, J., Pietrarelli, M., Singer, D. S., Kimura, S., Katoh, R., Kawaoi, A. , and Kohn, L. D. (1997) Proc. Natl. Acad. Sci. U. S. A. 95, 8251-8256). The ability of highly purified 27, 19, or 12 S follicular TG to suppress thyroid-restricted gene expression correlates with their ability to bind to FRTL-5 thyrocytes and is inhibited by a specific antibody to the thyroid apical membrane asialoglycoprotein receptor (ASGPR), which is related to the ASGPR of liver cells. Phosphorylating serine/threonine residues of TG, by autophosphorylation or protein kinase A, eliminates TG suppression and enhances transcript levels of the thyroid-restricted genes 2-fold in the absence of a change in TG binding to the ASGPR. Follicular TG suppression of thyroid-restricted genes is thus mediated by the ASPGR on the thyrocyte apical membrane and regulated by a signal system wherein phosphorylation of serine/threonine residues on the bound ligand is an important component. These data provide a hitherto unsuspected role for the ASGPR in transcriptional signaling, aside from its role in endocytosis. They establish a functional role for phosphorylated serine/threonine residues on the TG molecule.

Cloning and characterization of a calcium-sensing receptor from the hypercalcemic New Zealand white rabbit reveals unaltered responsiveness to extracellular calcium

The extracellular Ca2+ (Ca(0)2+)-sensing receptor (CaR) recently cloned from mammalian parathyroid, kidney, brain, and thyroid plays a central role in maintaining near constancy of Ca(0)2+. We previously showed that the hypercalcemia normally present in New Zealand white rabbits is associated with an elevated set point for Ca(02+)-regulated PTH release (the level of Ca(0)2+ half-maximally inhibiting hormonal secretion). This observation suggested an alteration in the Ca(02+)-sensing mechanism in the rabbit parathyroid, a possibility we have now pursued by isolating and characterizing the rabbit homolog of the CaR. The cloned rabbit kidney CaR (RabCaR) shares a high degree of overall homology (> 90% amino acid identity) with the bovine, human, and rat CaRs, although it differs slightly in several regions of the extracellular domain potentially involved in binding ligands. By Northern analysis and/or immunohistochemistry, a similar or identical receptor is also expressed in parathyroid, thyroid C cells, small and large intestine, and in the thick ascending limb and collecting ducts of the kidney. When expressed transiently in HEK293 cells and assayed functionally through CaR agonist-evoked increases in Ca(i)2+, the rabbit CaR shows apparent affinities for Ca(0)2+, Mg(0)2+, and Gd(0)3+ that are indistinguishable from those observed in studies carried out concomitantly using the human CaR. Therefore, at least as assessed by its ability to increase Ca(i)2+ when expressed in HEK293 cells, the intrinsic functional properties of the rabbit CaR cannot explain the hypercalcemia observed in vivo in the New Zealand white rabbit.

Urinary excretion of aquaporin-2 in humans: a potential marker of collecting duct responsiveness to vasopressin

The vasopressin-sensitive water channel (aquaporin 2; AQP-2) mediates water transport across the apical plasma membrane of the renal collecting ducts and is excreted in human urine. This study presents the hypothesis that measurements of the AQP-2 excretion rate might be used as a marker of collecting-duct responsiveness to vasopressin, and therefore could be useful in the clinical evaluation of various water-balance disorders. This study presents information about the development of an antibody to human AQP-2, and measures the urinary excretion of AQP-2 by quantitative Western analysis. A standard curve of band densities was generated by using known quantities of the modified immunizing peptide to derive the amount of AQP-2 contained in aliquots of urine. AQP-2 urinary excretion changed with short-term alterations in hydration status produced either by water loading (76% decrease, P < 0.01) or by 3% sodium chloride (760% increase, P < 0.01). Steady-state 24-h urinary excretion of AQP-2 was 43 +/- 10 nmol/24 h (or 28.5 +/- 6.9 pmol/mg creatinine), and 20 +/- 6 nmol/24 h (or 18.3 +/- 7.9 pmol/mg creatinine) in men and women, respectively. Therefore, urinary AQP-2 excretion can be quantified by using Western analysis, and may serve as a marker of collecting-duct responsiveness to vasopressin in different physiologic settings.

The effect of topical steroid on the actions of vasoconstrictor and vasodilator peptides in human skin

The effect of topical application of clobetasol propionate ointment (0.05% w/v) on the vascular changes induced by intradermal injections of histamine, calcitonin gene-related peptide, substance P, endothelin-1 and compound 48/80 was studied. Clobetasol propionate ointment was applied topically under occlusion to the forearm skin of healthy volunteers and vehicle base was applied to the contralateral forearm. The intradermal injections were made 4 h or, in a separate study, 72 h after topical steroid application. Responses were measured by planimetry and laser Doppler flowmetry. Four hours application of steroid did not significantly alter the responses to any of the vasoactive substances. After 72 hours application, clobetasol propionate significantly increased the size of the endothelin-1-induced area of vasoconstriction (p < 0.02) and significantly reduced the size of the flares induced by endothelin-1 (p < 0.02), substance P (p < 0.009) and compound 48/80 (p < 0.05). We conclude that the most likely explanation of our data is an inhibition by the steroid of cutaneous mast cell function.

Leiomyomatous hamartoma of the posterior tongue: a case report

A case of a rare leiomyomatous hamartoma arising in the posterior tongue of a sixteen-month-old male is reported. There has been no recurrence following simple excision and presenting symptoms of choking on swallowing have resolved. Most other leiomyomatous hamartomas in the upper aerodigestive tract have been reported in Japanese patients and have involved the maxillary gingiva and hard palate.

Ramsay Hunt syndrome mimicking acoustic neuroma on MRI

The authors present a case of Ramsay Hunt syndrome in whish the MRI appearance mimicked that of an intracanalicular acoustic neuroma.

Plant stems: a possible model system for the transduction of mechanical information in bone modeling

As a grass stem bends in the wind, signals at the subcellular level initiate a process of stem strengthening. The same happens in human bones. What have the two got in common?

Coupling of endothelin B receptors to the calcium pump and phospholipase C via Gs and Gq in rat liver

We have demonstrated in liver from male rats that both endothelin A (ETA) and ETB receptors coexist in equal proportion and that ETA receptors mediate a calcium-dependent activation of glycogenolysis. We describe here a sex difference in endothelin action in hepatocytes because, in female rats, 80% of the ET receptors are of ETB type and, accordingly, activation of glycogenolysis is an ETB-mediated process (EC50 = 0.03 pM). ET-1 stimulation of glycogenolysis in female rats was consecutive to activation of phosphatidylinositol 4,5-bisphosphate hydrolysis (EC50 = 0.03 pM) and to inhibition of the calcium extrusion pump (IC50 = 0.03 pM) in plasma membranes, with ET-1 approximately sarafotoxin S6C approximately ET-3. Endothelin regulation of each effector was potentiated by GTP gamma S. ET-1 did not stimulate adenylyl cyclase activity. To identify the nature of the guanine nucleotide regulatory proteins (G protein(s)) coupling ETB receptors to each effector, we used antibodies against the COOH terminus of different G protein alpha subunits. Antibodies reactive with Gs alpha (RM) blocked ET-1 inhibition of the calcium pump, while they did not affect ET-1 stimulation of phospholipase C. Antibodies reactive with Gq alpha (QL) dose-dependently antagonized stimulation of phospholipase C by ET-1 and vasopressin, without affecting ET-1 inhibition of the calcium pump. Antibodies reactive with Gi1 alpha/Gi2 alpha (AS) had no effect on either system. We conclude that the calcium signal provoked by endothelins in hepatocyte is not only consecutive to activation of phospholipase C but also to inhibition of the plasma membrane calcium pump, each effector being coupled to ETB receptors by different G proteins, Gq, and Gs.