Impact of Radiation on Dysphagia-Related Structures: A Dosimetric and Clinical Comparative Analysis of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT) Techniques in Patients With Head and Neck Cancer

Introduction Head and neck squamous cell carcinoma (HNSCC) is a significant health concern in India, with around one million new cases annually. The prevalence of HNSCC is notably high in Asia, especially in India, due to habits like tobacco chewing, betel nut usage, and alcohol consumption. Treatment typically involves a combination of surgery, radiation, chemotherapy, and biological therapy, aiming for tumor control while preserving function and quality of life. However, survivors often face long-term side effects like difficulty swallowing, leading to complications such as aspiration pneumonia. Intensity-modulated radiotherapy (IMRT) has shown promise in improving outcomes by sparing critical swallowing structures. Efforts to minimize radiation-related dysphagia are crucial for enhancing patients' quality of life post-treatment. Our study focuses on examining dosimetric parameters associated with dysphagia aspiration, alongside evaluating dysphagia grades in both treatment groups using the RTOG scale. Material and methods Patients with histologically confirmed non-metastatic head and neck carcinomas were included in our study in November 2018-April 2020. A total of 56 patients were taken into our study with 28 in each arm. They underwent radical radiotherapy (RT) with a total dose of 66-70 Gy, with or without concurrent chemotherapy, meeting specific inclusion criteria and excluding those receiving reirradiation or with distant metastasis. Patients were divided into two groups: Group I received three-dimensional conformal radiotherapy (3D-CRT), and Group II received IMRT. Treatment planning involved immobilization, CT imaging, delineation of target volumes and organs at risk, and contouring of swallowing structures. Dose-volume histogram parameters (mean dose, maximum dose, V30, V70, V80, D50, and D80) were used to assess mean dose to swallowing structures outside the planning target volume (PTV), with a mean dose constraint of 50 Gy. Dysphagia was evaluated using the RTOG criteria at baseline, during treatment, and six months post-treatment. Statistical analysis was performed using SPSS, with significance set at p < 0.05. Results In our study, the mean age at presentation differed slightly between the IMRT and 3D-CRT arms: 58 years versus 55 years, respectively. A higher proportion of patients in both arms experienced symptoms for three to six months, with 53.6% in 3D-CRT and 42.9% in IMRT. Stage distribution varied, with IV being most common in 3D-CRT and stage II in IMRT. Approximately 56% of patients in both groups had a history of smoking. Significant differences were observed in spinal cord dose between 3DCRT and IMRT techniques (p < 0.001). Similarly, a significant difference was found in the mean dose received by dysphagia aspiration-related structures (DARSs) between the 3D-CRT and IMRT arms (p = 0.04). Patients in the IMRT arm exhibited superior dysphagia grades compared to those in the 3D-CRT arm, with statistical significance observed in the third month (p = 0.008) and sixth month (p = 0.048). Conclusion Our study found a notable decrease in the mean DARS dose and reduced dysphagia severity at three and six months in the IMRT group compared to the 3D-CRT group. However, due to the diverse study population, establishing a definitive correlation between the DARS dose and dysphagia severity was challenging. Future large-scale studies are needed to validate these findings for improved preservation of DARS structures.

Patterns of Utilization and Outcomes of Perioperative Chemotherapy in Patients With Locally Advanced-urothelial Bladder Cancer (LABC)-Real World Data From an Indian Tertiary Care Cancer Center

AIM

Optimal utilization of perioperative systemic therapy in locally advanced bladder cancer (LABC) holds the key in improving the survival outcomes. We aim to analyze the oncological outcomes of clinically locally advanced urothelial bladder cancer patients treated with neoadjuvant (NACT) or adjuvant chemotherapy or without any systemic therapy in the perioperative period of radical cystectomy.

METHODS & MATERIAL

We retrospectively analyzed the medical records of patients with cancer of the urinary bladder diagnosed between 2012 and 2020. The demographic profile, and the treatment received, was recorded for all patients. Oncological outcomes of the patients based on these variables were analyzed.

RESULTS

Two hundred and twenty nine (229) locally advanced bladder cancer patients were included in the study. Eighty eight (38%) of them underwent upfront radical cystectomy and 141 (62%) received neoadjuvant chemotherapy (NACT). With a median follow-up of 27 months, the 2-year DFS in either of the groups was 65.4% and 67.1% respectively (P - 0.373). In the multivariate analysis, the pathological lymph nodal status and lymph vascular invasion (LVI) status influenced the DFS. The initial modality of management chosen did not affect the outcome. (HR - 0.688; 95% CI: 0.38-1.21). The commonest reason for not receiving NACT was Cisplatin ineligibility due to malignant obstructive uropathy and a subgroup analysis of this set of patients also did not show any significant difference in 2 year DFS compared to those who received NACT.

CONCLUSION

A significant proportion of patients with LABC are unable to receive the recommended neoadjuvant chemotherapy and obstructive uropathy is the commonest reason for this in our centre. In our single centre series upfront radical cystectomy followed by adjuvant platinum based therapy had an outcome similar to neoadjuvant chemotherapy in LABC patients, in patients who were unable to receive the same due to various reasons.

LBMON65 Generation Of Serum Insulin Like Growth Factor -1 (IGF-1) Normative Data According To Age, Tanner Staging & Bone Age In Healthy Indian Children And Adolescents With Two Different Assays: The Germinative Study

Context

To diagnose and monitor GH-related disorders, serum IGF-I is a cornerstone, but Indian ethnicity based data, following consensus criteria for establishment of normative data are not available.

Objectives

To generate normative IGF-I data for chronological age (CA), Tanner stage and bone age (BA) [Greulich & Pyle (GP)] for both genders. Setting and Participants: We conducted a cross-sectional epidemiological study for Indian children (age 5-18 years) that included 2226 apparently normal subjects (1145 males; 1081 females). We used robust clinical exclusion criteria initially and later statistically we removed outliers separately for Age,Tanner Stage & Bone age using software SPSS 26. 0. Outcome Measures:: Serum IGF-I (ng/ml) using the Roche ECLIA & Immunodiagnostic Systems & Immunoassay System (IDS iSYS) were measured and normative data for 2.5th, 5th,10th, 25th, 50th (median), 75th, 90th, 95th and 97.5th centiles were generated.

Results

Age- and gender-specific serum IGF-I normative data generated from a uniquely large cohort reflected various patterns. With Roche assay, females (n=910) had IGF-I median peak at 13 years (356.85) [BA (n=804) at 14 years (401.5 ng/mL)] and & Tanner (n = 936) stage IV (368) while males (n=959) had median peak at 14 years (329.5) [BA (n=906) at 15 years (351 ng/mL)] & Tanner (n = 986) stage III (311. 0). With IDS iSYS assay, females had IGF-I median peak at Age (n=913) 13 years (397.5), Tanner (n=941) stage IV (418.5) and GP BA (n=843) 14 years (448.5) and males had median peak at Age (n=974) 14 years (376), Tanner (n=1003) stage III (367) and GP BA (n=909) 15-16 years (383). Females had earlier rise & peak and higher IGF-I values with both assays. In Tanner-specific data maximum difference noticed between stage II and III in both genders with both assays. On comparison of both assays, IGF-1 median peak was achieved at similar ages and Tanner stage but all the values are higher with IDS iSYS assay. When reviewed published literature on Caucasians, females had IGF-I median peak at 15 years (300.1) and Tanner stage III (382.8) and males had median peak at 15 years (318.3) and Tanner stage IV (439). The Indian & Caucasian IGF-1 normative data clearly demonstrates that every ethnicity has a unique pattern of growth.

Conclusions

The normative data on serum IGF-I are ethnicity-specific and it will improve the diagnostic utility of IGF-I in evaluation and management of growth disorders in Indian Children. Using both age- and Tanner stage-specific normative data simultaneously can improve diagnostic work-up.

Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Screening for Beta Thalassemia Carrier State Among Women Attending Antenatal Clinic in a Tertiary Care Centre and Framing a Model Program for the Prevention of Beta Thalassemia

Aim

This study was carried out to detect beta (β) thalassemia heterozygous state in antenatal women and to create a validated flag in the software utilizing the screening indices to filter the samples to be subjected to high-performance liquid chromatography (HPLC) and to define a model for the prevention of thalassemia.

Methods

This cross-sectional study was carried out for a period of two years on women attending the antenatal clinic. Complete blood count (CBC) and peripheral smear were done during their first visit. Serum iron and total iron-binding capacity were done for women who had microcytic hypochromic anemia. The samples of women without iron deficiency were processed by HPLC for hemoglobinopathies. The spouses of women who were found to have beta thalassemia trait were counseled to undergo screening, and those who consented were tested.

Results

A total of 183 antenatal women were screened for hemoglobinopathies. Βeta thalassemia trait was detected in 23.5% of them. Among the 16 red blood cell (RBC) indices analyzed, Sehgal index and Mentzer index, both with sensitivities of 97.67%, were found to be suitable. Alert flag incorporated in the software of the analyzer to detect these indices helps not to miss samples to carry out HPLC. The spouses of women with β thalassemia trait who underwent HPLC testing were 55.81%. A model screening program was designed.

Conclusion 

Antenatal testing by HPLC should be done on all mothers having microcytic hypochromic anemia without iron deficiency. Spouse testing of the woman who was carriers denotes the success of the antenatal screening program.

Performance and energetic analysis of hydrodynamic cavitation and potential integration with existing advanced oxidation processes: A case study for real life greywater treatment

The current work is a "first of a kind" report on the feasibility and efficacy of hydrodynamic cavitation integrated Advanced Oxidation Processes (AOP's) towards treatment of a real life greywater stream in form of kitchen wastewater. The work has been carried out in a sequential manner starting with geometry optimization of orifice plate (cavitating device) followed by studying the effects of inlet pressure, pH, effluent dilution ratio on degradation of TOC and COD. Under optimized conditions of pH 3, 4 bar pressure, TOC and COD reduction of 18.23 and 25% were obtained using HC for a period of 120 min. To improve the performance of HC, further studies were carried out by integrating H₂O₂and O₃with HC. Using 5 g/h optimum dosage of H₂O₂, 87.5% reduction in COD was obtained beyond which it started decreasing. Moreover, integrating O₃(57.5% reduction in COD) increased the treatment cost. However, a hybrid process (HC + H₂O₂ + O₃) yielded 76.26 and 98.25% reductions in TOC and COD within60 min.The energetics of all the processes and the treatment costs were studied in detail and it was concluded that combined process of HC + H₂O₂ + O₃surpassed by far the performances of HC + H₂O₂and HC + O₃.

Alternative Chemotherapy Schedules in Ewing's Sarcoma: An Indian Perspective

Advances in the treatment of Ewing's sarcoma family of tumors (ESFTs) are a result of improvements in systemic and local therapies. VACA (vincristine, Adriamycin [doxorubicin], cyclophosphamide, dactinomycin) chemotherapy alone versus VACA + IE (VACA with alternate ifosfamide, etoposide) improve survival, but this regimen cannot be given to all patients due to poor tolerance and 5-day schedule chemotherapy in VACA + IE schedule. We reviewed the records of 50 patients treated as per our institutional protocols from 2007 to 2011. Two schedules of chemotherapy followed were vincristine, Adriamycin, cyclophosphamide (VAC) and VAC with alternate ifosfamide, etoposide (VAC + IE). Factors predictive of local failure and distant recurrence were analyzed. A total of 50 patients were analyzed. The median age at diagnosis was 14 years. Thirty-two patients were male, whereas 18 were female. Approximately, 95% of the patients relapsed after a median time gap of 1.6 years. The median 5-year disease-free survival was 30%. Systemic treatment with VAC or VAC + IE–based chemotherapy had equal local control and distant control rates. Smaller tumors had a better local control and lesser systemic failure than those of larger sizes. Successful treatment of Ewing's sarcoma requires optimal systemic and local therapy. Both the chemotherapy regimens showed equal survival rates. Control of both the local and distant diseases is a result of the combined modality approach. Stage at presentation is the most important factor for prognosis. Complete surgery and local radiotherapy are important predictive factors for local and systemic control.

Pyridoxine-dependent convulsions among children with refractory seizures: A 3-year follow-up study

Introduction:

Epilepsy accounts for 1% of the global disease burden and about 8–10 million epilepsy patients live in India. About 30–40% of these patients become drug-resistant and land up with palliative or disease-modifying surgeries. This is a situation causing great concern in view of the psychosocial and economic burden on the patient and the family apart from severe cognitive and motor consequences, especially in children. Therefore, it is mandatory to have an insight into the wide spectrum of causes with reference to refractoriness to antiepileptic medications in children with epilepsy.

Patients and Methods:

Children admitted under our team with refractory epilepsy as per the International League Against Epilepsy (ILAE) criteria in the last 3 years were included in the study.

Results:

Refractory epilepsy constituted 13.3% of inpatients in the pediatric group. Males dominated with 68.9% of these patients. Nearly 34.4% of these patients were found to suffer from various neurometabolic diseases. Almost 3.5% were due to pyridoxine-dependent convulsions. This group of patients showed an excellent response to dietary manipulation, disease-modifying treatment for the metabolic disorder, and supportive small-dose anticonvulsants. During follow-up, they showed very good response with reference to global development and seizure control.

Conclusion:

Pyridoxine-dependent convulsions are relatively rare forming about 3.5% of refractory epilepsies in this series. With initiation of appropriate therapy, results with reference to seizure control as well as neurodevelopment became evident within 2 weeks, and at 1-year follow-up, complete independence for majority of the needed activities is achieved with minimum cost, almost zero side effects, and absolute elimination of the need for palliative surgery.

Psychosocial Effects of Fractured Anterior Teeth among Rural Children

Aim: The aim of the study is to determine how rural children view children with visible incisor fracture.

Materials and methods: Class 7 (aged 11-12 years) and class 10 (aged 14-15 years) schoolchildren (the participants) were invited to make a social judgment about the color photograph of two children (the subjects). Participants were randomly allocated either (i) pictures of children without incisor fracture or (ii) pictures of the same children whose photographs had been digitally modified to visible incisor fracture. Using a child-centered questionnaire, participants rated subjects using a four-point Likert scale for three negative and six positive attributes. Total attribute scores were tested for significant differences, according to whether the subject had visible incisor fracture or not, using multivariate analysis of variance (p < 0.05).

Results: Both class 7 and 10 children rated subjects with visible incisor fracture more negatively than the subjects without incisor fracture. Female participants of class 10 have rated the male subject with incisor fracture significantly negatively (p < 0.01) than male subject without incisor fracture.

How to cite this article: Venkatesan R, Naveen M, Teja R, Paulindraraj S, Vallabhaneni SK, Arumugam SB. Psychosocial Effects of Fractured Anterior Teeth among Rural Children. Int J Clin Pediatr Dent 2016;9(2):128-130.

The role of the tissue renin-angiotensin system in the response of the rat adrenal to exogenous angiotensin II

The tissue renin-angiotensin systems (RAS) may have specific roles that complement those of the systemic RAS. In the adrenal, the tissue RAS has been implicated in the regulation of glomerulosa tissue growth and function, and in mediating the response of the tissue to stimulation by ACTH and potassium ions. To examine the role of the rat adrenal tissue RAS in its response to angiotensin II stimulation, adrenals were incubated either as bisected glands or as separated capsular glands (largely glomerulosa) under control conditions, or in the presence of the angiotensin-converting enzyme inhibitor captopril, or of angiotensin II, or both. Captopril inhibited the two different tissue preparations in different ways. In the capsular gland it inhibited basal aldosterone output, but facilitated its response to angiotensin II. In the bisected gland, captopril inhibited the response of aldosterone to angiotensin II. Other data suggest that one way in which captopril functions is by preventing the conversion of fasciculata-generated 18-hydroxydeoxycorticosterone (18-OH-DOC) to aldosterone in the glomerulosa. Immunolocalisation of 18-OH-DOC in perfused rat adrenal confirms that one function of angiotensin II is to mobilise tissue-sequestered 18-OH-DOC. The results illustrate the importance of tissue RAS in the synthesis of aldosterone and the response to angiotensin II.

Role of the tissue renin-angiotensin system in the response of the rat adrenal to exogenous angiotensin II

The tissue renin angiotensin systems (RAS) may have specific roles that complement those of the systemic RAS. In the adrenal, the tissue RAS has been implicated in mediating the response of the tissue to stimulation by ACTH and potassium ions, but its role in the response to angiotensin II stimulation has not been addressed. To examine this, rat adrenals were incubated either as bisected glands or as separated capsular glands (largely glomerulosa) under control conditions, or in the presence of the angiotensin converting enzyme inhibitor captopril, or of angiotensin II, or both. Captopril inhibited the two different tissue preparations in different ways. In the capsular gland it inhibited basal aldosterone output, but facilitated its response to angiotensin II. In the bisected gland, captopril inhibited the response of aldosterone to angiotensin II. The results illustrate the importance of the tissue RAS in the synthesis of aldosterone and the response to angiotensin II, and the two sets of data suggest that the fasciculata and glomerulosa zones interact in the formation of aldosterone. One way in which this may occur is by the mobilisation of fasciculata synthesised substrate, such as 18-hydroxydeoxycorticosterone (18-OH-DOC), for conversion by the glomerulosa, which is apparently supported by endogenous angiotensin II.

A two cell type theory for aldosterone biosynthesis: the roles of 11 beta-hydroxylase and aldosterone synthase, and a high capacity tightly binding steroid carrier for 18-hydroxydeoxycorticosterone in rat adrenals

Several lines of experimentation suggest that a tissue-sequestered pool of 18-hydroxydeoxycorticosterone (18-OH-DOC) in the rat adrenal may be mobilized as an aldosterone precursor. We show here that this steroid is maintained in a non-extractable form in the membranes of collagenase-dispersed fasciculata/reticularis cells. Because of this stability, the complex can be identified by immunocytochemistry and also, in IEF gels of solubilized inner adrenocortical zone membrane preparations, by immunoblotting. However, the complexed steroid cannot be extracted from the gels into organic solvent unless first treated with trypsin. Preincubation of viable whole glandular tissue with trypsin significantly enhanced aldosterone output and eliminated the trypsin-releasable 18-OH-DOC pool in IEF gels of solubilized inner zone membranes. Both prior sodium depletion and acute trypsin stimulation of whole glands enhanced extractable 18-OH-DOC in glomerulosa tissue membranes. Other experiments using in situ hybridization show that mRNA coding for 11 beta-hydroxylase (which generates 18-OH-DOC) is confined to the inner adrenocortical zones, whereas aldosterone synthase (which does not) is transcribed exclusively in the glomerulosa. The data suggest that a pool of 18-OH-DOC in inner zone membranes can be mobilized for utilization as an aldosterone precursor in the glomerulosa. The results also indicate the existence of an entirely novel tightly binding steroid carrier from which steroid cannot be extracted by organic solvent unless first subjected to proteolytic degradation.

Internalisation of the type I angiotensin II receptor (AT1) and angiotensin II function in the rat adrenal zona glomerulosa cell

Using a specific monoclonal antibody (6313/G2) to the first extracellular domain of the type 1 receptor (AT1), we showed that most of the receptor is internalised in the rat glomerulosa cell. When viable glomerulosa cells are incubated with 6313/G2, the receptor is transiently concentrated on the cell surface, and aldosterone output is stimulated. This stimulated output is enhanced by neither threshold nor maximal stimulatory concentrations of AII amide, although the antibody does not inhibit AII binding to the receptor. The antibody directly stimulates inositol trisphosphate (IP3) generation, but, while having no intrinsic action on protein kinase C (PKC) activation, it significantly inhibits the PKC response to angiotensin II. The data suggest that although the receptor is mostly internalized, recycling to the plasma membrane is constitutive, or regulated by unknown factors. Retention of the AT1 receptor in the membrane is alone enough to allow sufficient G protein interaction to generate maximal steroidogenic effects, through IP3 generation. PKC activation induced by angiotensin II has no bearing on steroidogenesis in the dispersed glomerulosa cell system.

Zonation, paracrine function and aldosterone secretion in the rat adrenal cortex

Using in situ hybridisation we show that, in the rat adrenal, 11 beta-hydroxylase is confined to the inner zones, whereas aldosterone synthase is expressed exclusively in the glomerulosa. Immunoblotting methods identify an 18-hydroxydeoxycorticosterone (18-OH-DOC) in IEF gels of solubilised inner adrenocortical zone membrane preparations. This steroid, which can also be identified by immunocytochemistry, cannot be solvent extracted from the IEF gels unless the gel slices are first treated with trypsin. Preincubation of viable whole glandular tissue with trypsin significantly enhances aldosterone output, and eliminates the trypsin releasable 18-OH-DOC pool in IEF gels. The data suggest that 18-OH-DOC is synthesised and sequestered in inner zone cells, in a novel non-solvent extractable manner, but can be mobilised for utilisation as an aldosterone precursor in the glomerulosa.

The relationship between the adrenal tissue renin-angiotensin system, internalization of the type I angiotensin II receptor (AT1) and angiotensin II function in the rat adrenal zona glomerulosa cell

Many data suggest that the elements of the tissue renin-angiotensin system (RAS) in the adrenal cortex are mostly located in the zona glomerulosa. The relationship of this paracrine/autocrine system with the cellular localization of the angiotensin II (AII) receptor has not bee clarified. Using a specific monoclonal antibody (6313/G2) to the first extracellular domain of the type 1 receptor (AT1), we show here that most of the receptor is internalized in the rat glomerulosa cell. This may result from tonic stimulation by the tissue RAS, and consequent permanent receptor occupancy. When viable glomerulosa cells are incubated with 6313/G2, the receptor is transiently concentrated on the cell surface, and aldosterone output is stimulated. This stimulated output is enhanced by neither threshold nor maximal stimulatory concentrations of AII amide, although the antibody does not inhibit AII binding to the receptor. The antibody directly stimulates inositol trisphosphate (IP3) generation, but, while having no intrinsic action on protein kinase C (PKC) activation, significantly inhibits the PKC response to angiotensin II. The data suggest that although the receptor is mostly internalized, recycling to the plasma membrane is constitutive, or regulated by unknown factors. Retention of the AT1 receptor in the membrane is alone enough to allow sufficient G protein interaction to generate maximal steroidogenic effects, through IP3 generation. PKC activation induced by angiotensin II has no bearing on steroidogenesis in the dispersed glomerulosa cell system.

Internalisation of the type I angiotensin II receptor (AT1) and angiotensin II function in the rat adrenal zona glomerulosa cell

Little is known about the cellular localisation of the angiotensin II (AII) type 1 receptor (AT1) in the rat adrenal glomerulosa cell, but some studies have suggested that receptor internalisation and recycling may occur. Using a specific monoclonal antibody (6313/G2) to the first extracellular domain, we show here that most of the receptor is internalised in the unstimulated cell. When viable glomerulosa cells are incubated with 6313/G2, the receptor is transiently concentrated on the cell surface, and aldosterone output is stimulated. This stimulated output is enhanced by neither threshold nor maximal stimulatory concentrations of AII amide, although the antibody does not inhibit AII binding to the receptor. Conversely, the stimulatory actions of the antibody and those of ACTH are additive. The data suggest that recycling to the plasma membrane is constitutive, or regulated by unknown factors. Retention of the AT1 receptor in the membrane is alone enough to allow sufficient G protein interaction to generate maximal stimulatory events.

Origin of aldosterone in trypsin-stimulated rat adrenal zona glomerulosa incubations

The time-course for the in-vitro secretion of aldosterone and 18-hydroxycorticosterone (18-OH-B) by rat adrenal whole capsular tissue (largely zona glomerulosa) was studied under control and stimulated conditions. The stimulatory effect of trypsin was relatively delayed, and the steroids were significantly enhanced only after 1 h, in contrast to the actions of ACTH, which produced effects after 15 or 30 min. Tissue-sequestered 18-hydroxydeoxycorticosterone (t-18-OH-DOC), which is not affected by ACTH, was significantly depleted by trypsin, but secreted 18-OH-DOC was not consistently affected by either stimulant. In contrast to the apparent mobilization of t-18-OH-DOC, the conversion of exogenously added [3H]18-OH-DOC to [3H]18-OH-B was inhibited by trypsin, and aldosterone was unaffected. When trilostane was added to inhibit de-novo steroidogenesis, under conditions in which the steroid secretory response to ACTH is completely inhibited, aldosterone and 18-OH-B secretion was still stimulated by trypsin although yields were lower. Compared with controls, trilostane reduced t-18-OH-DOC concentrations, and trypsin caused a further depletion. In other studies, glomerulosa plasma membrane enriched preparations were homogenized and centrifuged, and the supernatants were dialysed and added to incubations of dispersed zona glomerulosa cells in the presence or absence of stimulators of aldosterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

The biosynthesis of aldosterone

The cellular mechanisms for aldosterone biosynthesis are incompletely understood. Although the enzymes involved are now well characterized, the dynamics of aldosterone secretion in a variety of rat adrenal preparations are not consistent with the concept that freshly synthesized corticosterone is an important intermediate. In whole glomerulosa tissue preparations, aldosterone is more readily formed from endogenous precursors than from an added radioactive precursor, such as [3H]pregnenolone, and in the in situ perfused gland preparation, aldosterone responses to stimulation, for example by ACTH, are significantly more rapid than those of corticosterone, suggesting a tissue source of steroid substrate for aldosterone production other than corticosterone. The only steroid which is stored in rat adrenal glomerulosa tissue to any extent is 18-hydroxydeoxycorticosterone (18-OH-DOC), and this pool has been located in plasma membrane fractions. It is lost on preparation of collagenase dispersed glomerulosa cells. Since dispersed glomerulosa cell preparations produce significantly less aldosterone, relative to corticosterone, than incubated intact whole glomerulosa, it is plausible that this tissue pool (which is not found in the inner zones) is the immediate precursor for aldosterone formation. Further evidence shows that trypsin, which stimulates aldosterone (and 18-hydroxycorticosterone) production in rat intact glomerulosa tissue, but not in dispersed cells, stimulates translocation of protein kinase C to the plasma membrane. It is plausible that one function of protein kinase C in the rat adrenal zona glomerulosa is to mobilize membrane sequestered 18-OH-DOC for conversion to aldosterone.

The role of endothelin in the control of adrenocortical function: stimulation of endothelin release by ACTH and the effects of endothelin-1 and endothelin-3 on steroidogenesis in rat and human adrenocortical cells

The rate of blood flow through the intact adrenal gland is closely linked to steroid hormone secretion, and although the mechanism involved is unknown, it is thought to involve secretory products of the vascular endothelium. In dispersed cell preparations, endothelin-1 and -3 both caused a dose-dependent and highly sensitive increase in steroid secretion by zona glomerulosa and zona fasciculata cells of the rat and human adrenal cortex. In addition, when the perfused rat adrenal was stimulated with ACTH, significant increases in steroid secretion and perfusion medium flow rate were accompanied by significantly increased secretion of immunoreactive endothelin into the adrenal vein. It is proposed that endothelin has a role in mediating the adrenocortical response to ACTH stimulation.

Control of steroidogenesis by the calcium messenger system in human adrenocortical cells

The involvement of the calcium messenger system in the control of steroidogenesis in the rat and bovine adrenal cortex has been studied extensively. However the role of these second messengers in the control of human adrenocortical function is not established. This was therefore studied by incubating collagenase-dispersed human adrenocortical cells with the calcium ionophore A23187 and the protein kinase C activator phorbol 12-myristate 13-acetate (TPA). The effects of the calcium channel blocker verapamil on basal and stimulated steroidogenesis were also studied. Both TPA (1 pmol/l-10 mumol/l) and A23187 (1 nmol/l-10 mumol/l) caused a dose-dependent increase in cortisol, aldosterone and corticosterone production. Verapamil (10 mumol/l) inhibited the increase in aldosterone, corticosterone and cortisol produced in response to ACTH(1-24), potassium, and desacetyl-alpha MSH. Unlike previous results in the rat, these effects were not specific for aldosterone secretion. The results suggest that, as in other species, calcium mobilization and protein kinase C activation have a role in the control of steroidogenesis in the human adrenal cortex. However, in contrast to the rat, these mechanisms appear to be involved in the control of steroidogenesis in both the zona glomerulosa and inner zone cells.

The relationship between adrenal vascular events and steroid secretion: the role of mast cells and endothelin

The actions of ACTH on the adrenal cortex are known to be 2-fold. In addition to increased steroidogenesis, ACTH also causes marked vasodilation, reflected by an increased rate of blood flow through the gland. Our studies, using the in situ isolated perfused rat adrenal preparation, have shown that zona fasciculata function and corticosterone secretion are closely related to vascular events, with an increase in perfusion medium flow rate causing an increase in corticosterone secretion, in the absence of any known stimulant. These observations give rise to two important questions: how does ACTH stimulate blood flow; and how does increased blood (or perfusion medium) flow stimulate steroidogenesis? Addressing the first question, we have recently identified mast cells in the adrenal capsule, and shown that Compound 48/80, a mast cell degranulator, mimics the actions of ACTH on adrenal blood flow and corticosterone secretion. We have also demonstrated an inhibition of the adrenal vascular response to ACTH in the presence of disodium cromoglycate, which prevents mast cell degranulation. We conclude, therefore, that ACTH stimulates adrenal blood flow by its actions on mast cells in the adrenal capsule. Addressing the second question, we looked at the role of endothelin in the rat adrenal cortex. Endothelin 1, 2 and 3 caused significant stimulation of steroid secretion by collagenase dispersed cells from both the zona glomerulosa and the zona fasciculata. A sensitive response was seen, with significant stimulation at an endothelin concentration of 10(-13) mol/l or lower. Endothelin secretion by the in situ isolated perfused rat adrenal gland was measured using the Amersham assay kit. Administration of ACTH (300 fmol) caused an increase in the rate of immunoreactive endothelin secretion, from an average of 28.7 +/- 2.6 to 52.6 +/- 6 fmol/10 min (P less than 0.01, n = 5). An increase in immunoreactive endothelin secretion was also seen in response to histamine, an adrenal vasodilator, which stimulates corticosterone secretion in the intact gland, but has no effect on collagenase-dispersed cells. From these data we conclude that endothelin may mediate the effects of vasodilation on corticosterone secretion, and this mechanism may explain some of the differences in response characteristics between the intact gland and dispersed cells.

Effect of the endothelins on aldosterone secretion by rat zona glomerulosa cells in vitro

Endothelins are thought to be involved in the local regulation of blood flow and tissue function. These experiments were carried out to investigate the possible role of endothelins in the control of aldosterone secretion by the rat adrenal. Suspensions of zona glomerulosa cells were prepared by collagenase digestion of capsular tissue, and incubated in the presence of increasing concentrations of endothelin. Aldosterone was measured by RIA. All three peptides caused a dose-dependent increase in the secretion rate of aldosterone by zona glomerulosa cells. The minimum concentration of peptide required to give a significant response was 10(-14) mol/l for endothelins 2 and 3 and 10(-13) mol/l for endothelin 1. At a concentration of 10(-7) mol/l endothelin 2 elicited a 20-fold increase over basal aldosterone secretion, while both endothelins 1 and 3 elicited a 30-fold increase (P less than 0.001 in all cases). These results show that the endothelins are potent stimulators of aldosterone secretion, and suggest that these peptides may have a role in the control of zona glomerulosa function.

Trypsin stimulation of aldosterone and 18-hydroxycorticosterone production by rat adrenal zona glomerulosa tissue is mediated by activation of protein kinase C

When rat adrenal whole capsules, containing the zona glomerulosa, were incubated, addition of the protein kinase C inhibitors TMB-8 (10 mumol/l), W7, H7, polymyxin-B and sphingosine (all 1 mumol/l) was found to inhibit the steroidogenic response to trypsin. Aldosterone and 18-hydroxycorticosterone were strongly, and corticosterone moderately, affected, while the production of 18-hydroxydeoxy-corticosterone was neither stimulated by trypsin nor inhibited by the protein kinase C inhibitors. Addition of neomycin, which prevents substrate interaction with phospholipase C, also inhibited the response to trypsin, while addition of phospholipase C itself stimulated aldosterone, 18-hydroxycorticosterone and corticosterone production with the same tissue sensitivity as trypsin. Addition of phospholipase A2 had no effect. Direct assay of protein kinase C activity showed that trypsin stimulation effected the translocation of Ca2+/phospholipid-activated protein kinase C from the cytosolic to the membrane fraction. When glomerulosa tissue was incubated with [32P]ATP, and cytosolic proteins were subjected to isoelectric focusing on polyacrylamide gels, autoradiography showed that incorporation of 32P into several protein components was increased by trypsin stimulation. It was concluded that trypsin exerts its stimulatory effects on steroidogenesis by activating protein kinase C; not, however, by generating the Ca2+/phospholipid-independent fragment, but possibly by enhancing the activity of phospholipase C.