Correlación entre estudios diagnósticos prequirúrgicos y hallazgos operatorios en el hiperparatiroidismo primario / Correlation between pre-surgical diagnosis studies and the surgical findings in primary hyperparathyroidism

El hiperparatiroidismo primario (HPT 1°) se caracteriza por presentar niveles elevados de calcio(Ca) en sangre debido a un exceso en la producción de parathormona (Pth) por parte de las glándulasparatiroides (GP). El tratamiento primario es quirúrgico.En la actualidad, la utilización de métodos imagenológicos de localización preoperatorio facilitansu ubicación, disminuyen los tiempos quirúrgicos, laestadía hospitalaria y en ocasiones otorgan la posibilidadde abordajes de invasión mínima. El objetivo principalde este trabajo es determinar la correlación entre elhallazgo operatorio y los estudios de localización preoperatoria, pudiendo valorar de esta manera la utilidadde dichos estudios.RESULTADOS: Al total de la muestra se le realizó Centellograma y Ecografía y se los consideró positivocuando identificaron la presencia de una o más glándulasaumentadas de tamaño. En 43 casos la ecografíafue positiva (71.6 %). En relación a la gammagrafía en52 casos fue positiva (86.6%). En aquellos casos en loscuales ambos estudios de localización preoperatoriafueron positivos y coincidentes entre sí, se correspondierontambién con el hallazgo operatorio. Cuatro pacientes merecieron un análisis particular debido a las característicasde su presentación y hallazgos quirúrgicos obtenidos.CONCLUSIONES: Si bien los estudios de localizaciónprequirúrgicos son importantes en el manejo de estapatología, no coinciden en todos los casos con los hallazgosoperatorios.En relación a esto, es necesario un amplio conocimientodel cirujano especializado de los aspectosembriológicos y anatómicos de las glándulasparatiroides.Tales aspectos son indispensables en la exploraciónregional y el abordaje bilateral para la identificación deectopías y patología multiglandular...

Primary hyperparathyroidism (PYH1)is a pathology characterized for presenting high levels ofcalcium in the blood due to an excess of Parathyroidhormone (PTH) production by the parathyroid glands. The primary treatment is surgery. Currently, the use ofpre-surgical localized images studies help provideposition, diminishes the surgical time as well as the hospitalstay and in some occasions offers the possibility ofminimal invasion approach. The main goal of this workis to determine the correlation between surgical findingsand pre-surgical localization studies, being able to valuethe use of such studies. RESULTS: All samples underwent ultrasound andscintigraphy, it was considered positive to those were thepresence and identification of one or more glandsincreased in size. In 43 cases the ultrasound was positive(71.6%). Regarding the gammagraphy, 52 cases werepositive (86.6%). In cases were both methods of presurgicallocalization were positive, they were also inaccordance with the surgical findings in all cases. Only4 patients required a specific analysis because of itscharacteristics in display and surgical findings previouslyobtained.CONCLUSIONS: Although the pre-surgical localizedstudies are important when managing this pathology, theydo not meet in all the cases with surgical findings. Inrelation to this, it is necessary for a surgeon to have awide specialized knowledge regarding embryological andanatomical aspects of parathyroid glands. This isessential in regional exploration and bilateral approachfor identifying ectopic and multi-glandular pathologies...

Thyrotropin-secreting pituitary adenomas: biological and molecular features, diagnosis and therapy.

Central hyperthyroidism due to a thyrotropin (TSH)-secreting pituitary adenoma is a rare cause of hyperthyroidism, representing 0.5-1.0% of all pituitary adenomas. The etiopathogenesis of TSH-secreting-adenomas is unknown and no definite role for various oncogenes has been proven. Patients with TSH-secreting adenoma usually present with signs and symptoms of hyperthyroidism milder than those in patients with hyperthyroidism of thyroid origin, in addition to symptoms secondary to mass effects of the pituitary tumour. Mixed pituitary tumours co-secrete growth hormone and prolactin. The characteristic biochemical abnormalities are normal or high serum TSH concentrations in the presence of elevated total and/or free thyroid hormones concentrations. Measurement of markers of peripheral thyroid hormone action and dynamic tests may aid in the differential diagnosis with the syndrome of resistance to thyroid hormone. Neuroimaging is fundamental to visualize the pituitary tumor. Therapy of TSH-secreting adenomas can be accomplished by surgery, radiation therapies, and medical treatment with somatostatin analogs or dopamine agonists. Nowadays, and in contrast with the first reports on this rare disease, most patients are well controlled by current therapies.

Effectiveness of frequency-modulated electromagnetic neural stimulation in the treatment of painful diabetic neuropathy.

AIMS/HYPOTHESIS: The largely unsatisfactory results reported for the pharmacological treatment of diabetic neuropathy has spurred the search for alternative therapies. The aim of this study was to evaluate the efficacy of frequency-modulated electromagnetic neural stimulation (FREMS) as a novel treatment for painful diabetic neuropathy. METHODS: Patients (n=31) with painful neuropathy associated with decreased nerve conduction velocity (<40 m/s) and increased vibration perception threshold (>25 V) were enrolled in a randomised, double-blind, crossover study designed to compare the effects of FREMS with those of placebo. Each patient received two series of ten treatments of either FREMS or placebo in random sequence, with each series lasting no more than 3 weeks. The primary efficacy end point was the change in pain measured by a visual analogue scale (VAS). RESULTS: FREMS induced a significant reduction in daytime and night-time VAS pain score (all p<0.02). Furthermore, FREMS induced a significant increase in sensory tactile perception, as assessed by monofilament; a decrease in foot vibration perception threshold, as measured by a biothesiometer; and an increase in motor nerve conduction velocity (all p<0.01). No significant changes were observed after placebo. Comparison of measurements at the 4-month follow-up with those at baseline revealed that a significant benefit persisted for all measures that showed an improvement at the end of treatment, with an additional improvement in quality of life evaluated by the Short Form-36 questionnaire (all p<0.05). No significant side effects were recorded during the study. CONCLUSIONS/INTERPRETATION: FREMS is a safe and effective therapy for neuropathic pain in patients with diabetes and is able to modify some parameters of peripheral nerve function.

IFN-alpha 1 gene expression into a metastatic murine adenocarcinoma (TS/A) results in CD8+ T cell-mediated tumor rejection and development of antitumor immunity. Comparative studies with IFN-gamma-producing TS/A cells.

Cells from a spontaneous, invasive, and metastasizing mouse mammary adenocarcinoma (TS/A-pc) were transfected with a retroviral vector containing the mouse IFN-alpha 1 gene. TS/A clones secreting varying amounts of IFN-alpha 1 were isolated and their tumorigenicity was evaluated after s.c. or i.v. injection into immunocompetent BALB/c mice. Almost all of the IFN-alpha-secreting TS/A clones failed to grow in a high percentage of mice or formed small tumors after a long latency time, whereas TS/A-pc or transfection control cells always grew into large s.c. tumors. Rejection was mainly mediated by CD8+ T lymphocytes and partially by polymorphonuclear cells, as demonstrated by selective immunosuppression experiments and histologic and ultrastructural data. After rejection, a significant portion of mice displayed an immune resistance to the subsequent challenge with TS/A-pc. When the metastatic ability of IFN-alpha-secreting clones was compared with that of previously characterized IFN-gamma-secreting TS/A clones, it was found that the expression of IFN-alpha into TS/A tumor cells resulted in a potent inhibition of metastases formation, whereas IFN-gamma expression either did not affect or even enhanced the metastatic behavior of TS/A cells. These results provide strong evidence for the usefulness of IFN-alpha-producing tumor cells for the development of gene therapy strategies and vaccines against metastatic tumors.

Basic fibroblast growth factor enhances testosterone secretion in cultured porcine Leydig cells: site(s) of action.

The effect and mechanism of action of basic fibroblast growth factor (bFGF) on testicular steroidogenesis were investigated using as a model primary cultures of purified porcine Leydig cells from immature intact animals. Basic FGF increased basal and human chorionic gonadotrophin (hCG)-induced testosterone accumulation (with an ED50 of 0.64 ng/ml bFGF, 35 pM) in the medium following a long-term treatment. The effects of bFGF (10 ng/ml, 72 h) were found at all hCG concentrations tested (0.001-1 ng/ml), the growth factor affecting the maximal steroidogenic capacity of the Leydig cells but not their sensitivity to the gonadotrophin. In this context, we have therefore investigated whether the stimulatory effect of bFGF on testosterone formation was related to an increase of the steroidogenic enzyme activities. The data obtained indicate that the growth factor did not affect the gonadotrophin action on the formation of delta 5-steroid hormone, namely dehydroepiandrosterone (DHEA) (evaluated in the presence of 10(-5) M WIN 24540, an inhibitor of 3 beta-hydroxysteroid dehydrogenase/isomerase). By contrast, bFGF (10 ng/ml, 72 h) was found to increase in a comparable manner the conversion of pregnenolone, DHEA and delta 4-androstenedione into testosterone, suggesting a stimulatory effect on 17 beta-hydroxysteroid dehydrogenase activity. Indeed, bFGF enhanced in a dose-dependent manner (ED50 = 39 pM) this enzyme activity evaluated through the conversion of delta 4-androstenedione to testosterone. These effects of bFGF on Leydig cell steroidogenic activity are probably exerted through specific membrane bFGF receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of activin A on dehydroepiandrosterone and testosterone secretion by primary immature porcine Leydig cells.

In the present study, we evaluated the effect of the homodimer activin A on immature porcine Leydig cell functions in primary culture. Activin A (0.5-100 ng/ml) reduced hCG-stimulated dehydroepiandrosterone (DHEA) accumulation in a dose- and time-dependent manner, with a maximal inhibitory effect (58% decrease) at 20 ng/ml (8 x 10(-10) M). Activin A was found not to control steroidogenesis, either through a modulation of the gonadotropin LH/hCG binding or low-density lipoprotein cholesterol binding and internalization. However, activin A significantly decreased pregnenolone (p less than 0.002) and DHEA (p less than 0.001) formation (evaluated in the presence of 10(-5) M of WIN 24540, an inhibitor of 3 beta-hydroxysteroid dehydrogenase/isomerase [3 beta-HSDI]activity) in Leydig cells maximally stimulated with hCG (3 ng/ml, 3 h) or incubated in the presence of 22R-hydroxycholesterol (5 micrograms/ml, 2 h). These findings indicate that activin A probably exerts a partial inhibitory effect on cholesterol side-chain cleavage cytochrome P450 (P450scc) activity. On the other hand, activin A significantly (p less than 0.001) enhanced the conversion of exogenous pregnenolone and DHEA (500 ng/ml) but not of progesterone and androstenedione (500 ng/ml) into testosterone, suggesting that activin A potentially enhances 3 beta-HSDI activity in Leydig cells. Activin A action on 3 beta-HSDI activity was found to be closely related to that of transforming growth factor-beta 1 (TGF beta 1), since both activin A (20 ng/ml) and TGF beta 1 (2 ng/ml) induced a comparable and non-additive increase in 3 beta-HSDI activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermal growth factor directly stimulates steroidogenesis in primary cultures of porcine Leydig cells: actions and sites of action.

The actions and the mechanisms of action of epidermal growth factor (EGF) in testicular steroidogenesis were investigated using a model of primary culture of purified porcine Leydig cells from immature intact animals. EGF decreased (1.7-fold) human CG (hCG)-induced dehydroepiandrosterone (DHEA) accumulation in the medium whereas it enhanced (2.5-fold) that of testosterone. The maximal and half-maximal effects on both DHEA and testosterone secretions were observed at similar concentrations which were, respectively, 3 (5 x 10(-10) M) and 0.7 (11 x 10(-11) M) ng/ml EGF, after 72-h treatment. EGF effect on DHEA and testosterone secretion was similarly observed whether the cells were acutely (3 h) stimulated with hCG (1 ng/ml) or with 8-bromo-cAMP (10(-3) M). To further localize the steroidogenic biochemical steps affected by EGF, the growth factor action on steroidogenic enzyme activities was investigated. EGF increased delta 5 steroid intermediate (i.e. pregnenolone and DHEA) formation [evaluated in the presence of 10(-5) M of WIN 24540, an inhibitor of 3 beta-hydroxysteroid dehydrogenase/iosomerase (3 beta-HSDI) activity]. However, this stimulation was observed in cells when acutely (3 h) stimulated with hCG (0.01-1 ng/ml) but not when incubated with 22R-hydroxycholesterol (0.01-10 micrograms/ml). Such findings indicate that EGF did not affect cholesterol side chain cleavage cytochrome P450 activity but probably increased cholesterol substrate availability for this enzyme in the inner mitochondria. Moreover, EGF significantly (P less than 0.001) increased delta 5 steroid intermediate (i.e. pregnenolone and DHEA) but not delta 4 steroid intermediate (i.e. progesterone and androstenedione) conversion into testosterone, indicating that EGF enhances 3 beta-HSDI activity. Such effects of EGF are directly exerted on Leydig cells since EGF receptors (Kd = 16 x 10(-11) M) are present in primary cultures of purified porcine Leydig cells. Together, the present findings show that in Leydig cells from intact animals, EGF enhances the gonadotropin action on testosterone formation through an increase in the availability of cholesterol substrate in the mitochondria as well as an increase in the activity of 3 beta-HSDI.

[Interaction between gonadotropins and "Transforming Growth Factor Beta" (TGF Beta) in testicular function control]. / Interactions entre les gonadotrphines et le "Transforming Growth Factor beta " (TGF beta) dans le contröle des fonctions testiculaires.

Testicular function is regulated not only by circulating hormones, among which the gonadotrophins play the main role, but also by local factors originating in multiple and complex interactions among cells. In this review, the example of gonadotrophins (LH and FSH) and Transforming Growth Factor beta (TGF beta) was chosen to illustrate the role of interactions between circulating hormones and gonadal growth factors in testicular function control; TGF beta-like activity has been found in the male gonad and we have used a model of cultured purified testicular cells to show that the action of TGF beta on testicular function mainly involves antagonism of the effect of gonadotrophins. Conversely, TGF beta promotes differentiated Leydig and Sertoli cell function. The example of interactions between TGF beta and gonadotrophins reported here shows that locally produced growth factors can regulate the response of testicular cells to gonadotrophins, a finding that extends our concept of reproductive endocrinology to cell-cell interactions.

[The effect of food intake on drug action]. / Beeinflussung der Arzneimittelwirkung durch Nahrungseinnahme.

Interactions between medicaments and food are only incompletely documented--despite their frequent occurrence. Food can influence the effect of medicaments in a variety of ways: the effect of the medicament can be delayed or weakened; in some cases the effect may also be increased. The interactions between the kinetics of medicaments and food are described in the present survey. The absorption conditions in the stomach and small intestine are influenced physiologically and chemically by food. In very rare cases the elimination of active ingredients too can be modified by the quality and quantity of the food. Detailed knowledge about the physical-chemical properties of the medicaments used help to optimize the pharmacotherapy in the individual case. For the patient, the easiest suggestion to follow would be to take the medicaments with plenty of water and always at the same time.

On the mechanisms involved in the inhibitory and stimulating actions of transforming growth factor-beta on porcine testicular steroidogenesis: an in vitro study.

By using immature porcine Leydig cells cultured in defined medium as a model, transforming growth factor-beta (TGF beta) was shown to exert a dramatic inhibitory effect on their basal and human chorionic gonadotropin (hCG) (or 8-bromo-cyclic AMP) stimulated dehydroepiandrosterone secretion, in the presence or absence of saturating concentrations of exogenous (low density lipoprotein) cholesterol substrate. In contrast, TGF beta exerted both a stimulating and inhibitory effect on testosterone secretion: while hCG-stimulated testosterone secretion was enhanced by low doses of TGF beta (0.06-0.4 ng/ml, 48 h), it was decreased with higher concentrations of TGF beta (2.5-10 ng/ml, 48 h). The data obtained show that the inhibitory action of TGF beta on testicular steroidogenesis was related to a decrease in pregnenolone formation by affecting a step(s) distal to cyclic AMP formation but before cholesterol association with cytochrome P-450 side-chain cleavage. As for the stimulatory effect of TGF beta on testosterone formation, this was mainly related to an increase (about 2-fold) in 3 beta-hydroxysteroid dehydrogenase/isomerase activity (ED50 0.05 ng/ml, 2 X 10(-13) M). The results indicate that the (short-term) steroidogenic stimulatory action of luteinizing hormone (LH)/hCG is antagonized by high concentrations of TGF beta by decreasing pregnenolone formation while it is enhanced by the stimulating action of low concentrations of TGF beta exerted on 3 beta-hydroxy steroid dehydrogenase/isomerase activity.

Partial 17, 20-desmolase and 17 alpha-hydroxylase deficiencies in a 16-year-old boy.

Thirteen plasma steroids as well as ACTH, LH and FSH were measured by specific RIAs under basal and dynamic conditions in a 16-year-old boy (normal external genitalia, 46, XY karyotype) who presented slowness and unachievement of pubertal development. On the delta 4-pathway: basal levels of testosterone and dihydrotestosterone were low- with a normal ratio-, delta 4-androstenedione and 11 beta-hydroxyandrostenedione were in the low normal range. Meanwhile, 17 alpha-hydroxyprogesterone and progesterone levels were markedly elevated. On the delta 5-pathway: dehydroepiandrosterone was extremely low while 17 alpha-hydroxypregnenolone and pregnenolone were almost normal; dehydroepiandrosterone sulfate was subnormal while pregnenolone sulfate was normal. Cortisol, aldosterone were normal while ACTH was moderately increased. Basal and responsive levels of LH and FSH were markedly increased. ACTH stimulation induced a subnormal rise of cortisol and 11 beta-hydroxyandrostenedione, a low or absent rise of dehydroepiandrosterone, 17 alpha-hydroxypregnenolone, androstenedione and 17 alpha-hydroxyprogesterone contrasting with a marked rise of pregnenolone and progesterone. After hCG stimulation, responses were low for testosterone, extremely high for 17 alpha-hydroxyprogesterone with a normalisation of the 17 alpha-hydroxyprogesterone/progesterone ratio. Fluoxymesterone dramatically reduced the pathologically high basal levels of progesterone and 17 alpha hydroxyprogesterone. Dexamethasone induced only a minute decrease in the delta 4-progestagens, a marked decrease in pregnenolone, with a more than 80% reduction of 17 alpha- hydroxypregnenolone, dehydroepiandrosterone, dehydroepiandrosterone sulfate and androstenedione. These data suggest a defect involving the cytochrome P450 common to both 17 alpha-hydroxylase and 17, 20-desmolase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

[Malignant arterial hypertension disclosing late congenital adrenal hyperplasia due to 17 alpha-hydroxylase deficiency]. / Hypertension artérielle maligne révélant tardivement une hyperplasie congénitale des surrénales par déficit en 17 alpha-hydroxylase.

17 alpha-hydroxylase deficiency is a rare form of congenital abnormality in steroid synthesis, usually associated with moderate arterial hypertension and suppression of the renin-angiotensin system in a young adult. We report on a 45 years old woman with malignant hypertension (220/135 mmHg, severe retinopathy with papilledema, progressive renal insufficiency with serum creatinine over 300 mumol/l) of recent onset. Biological exploration revealed a metabolic alkalosis, a moderate hypokalemia (3 mmol/l), with elevated urinary excretion of potassium. Plasma aldosterone concentration (33 ng/dl) and plasma renin activity (17 ng/ml/h) were elevated. Acute captopril administration was followed by a marked (-29 p. 100) decrease in mean arterial pressure. In this 46 XX patient, a primary amenorrhea had never been explored; clinical examination disclosed the absence of female secondary sex characteristics. Plasma cortisol was low (203 mmol/l) as were plasma androgens (testosterone 0.55, androstene dione 0.19, delta HEA less than 0.1 nmol/l respectively) and oestrogens (oestradiol 59 nmol/l). Elevated levels of progesterone and pregnenolone sulfate (12.1 and 2027 nmol/l respectively) contrasted with decreased levels of 17 OH progesterone (0.35 nmol/l). Computed tomography revealed a subnormal right adrenal gland and a pseudo-tumoral aspect on the left side. Treatment with dexamethasone and combined antihypertensive drugs (captopril, nifedipine and atenolol) resulted in normalisation of blood pressure and secretion of renin and aldosterone but renal function did not fully recovered. Thus, the hypertension of 17 alpha-hydroxylase deficiency can follow a malignant course in association with a marked activation of the renin-angiotensin system.

Direct regulating effects of transforming growth factor beta on the Leydig cell steroidogenesis in primary culture.

The effect of transforming growth factor beta on testicular steroidogenesis was studied by using a model of immature porcine Leydig cells cultured in a chemically defined medium. Leydig cells were cultured in the presence of human or porcine purified TGF beta and the following parameters were measured: cell proliferation, LH/hCG binding, and hCG-stimulated steroid hormone productions (DHEA, DHEAS and testosterone). Whereas TGF beta from the two sources had no effect on Leydig cell multiplication, it markedly inhibited LH/hCG-stimulated DHEA and DHEAS in a time- and dose-dependent manner. The maximal inhibitory effect of this peptide on LH/hCG binding (65% decrease), hCG-stimulated DHEA (77% decrease) and DHEAS (92% decrease) productions was observed with 2 ng/ml for 48 h of treatment. In contrast, TGF beta exerted a biphasic effect on hCG-stimulated testosterone production: stimulating (110% increase) until 2 ng/ml and inhibiting (35% decrease) for higher concentrations. [125I]TGF beta was cross-linked to Leydig cells using disuccinimidyl suberate; cells affinity labelled with [125I]TGF beta exhibit a major labelled band of approx 280 kDa, which has the properties expected from a TGF beta receptor. These data demonstrate that TGF beta is a direct potent regulator of Leydig cell steroidogenic function and its effects are probably mediated via a specific receptor.

Acetylation of acetylhydrazine, the toxic metabolite of isoniazid, in humans. Inhibition by concomitant administration of isoniazid.

The effect of isoniazid and its metabolites on the disposition of acetylhydrazine, a toxic metabolite formed from isoniazid, was studied in humans. Acetylhydrazine was administered i.v. with and without prior ingestion of 300 mg of isoniazid. In the studies with isoniazid, 15N2-acetylhydrazine was administered in order to distinguish exogenous acetylhydrazine from the unlabeled acetylhydrazine formed from isoniazid. In each subject (two fast and three slow acetylators) the rate of elimination of acetylhydrazine was similar to the rate of elimination of isoniazid suggesting that the two compounds are subject to the same acetylation polymorphism. In the presence of isoniazid the rate of elimination of acetylhydrazine was consistently lower than in the absence of isoniazid, and the urinary excretion of diacetylhydrazine and the ratio of diacetyl/acetylhydrazine in urine decreased. The data indicate that therapeutic concentrations of isoniazid and its metabolites inhibit the acetylation of acetylhydrazine in humans. The inhibition of this detoxification pathway could contribute to the hepatotoxicity of isoniazid.

Somatomedin C/insulin-like growth factor 1 as a possible intratesticular regulator of Leydig cell activity.

By using immature porcine Sertoli cells cultured in serum-free defined medium, we report that Sertoli cell-conditioned medium (SCCM) contains immunoreactive somatomedin C/insulin-like growth factor 1 (ir-SmC/IGF 1) which dilutes in parallel with purified human SmC/IGF 1. The release of ir-SmC/IGF 1 in the culture medium was dependent on the exposure time to Sertoli cells: no measurable ir-SmC/IGF 1 at 8 h, 12.1 +/- 1.2 ng/10(6) cells at 24 h and 33.9 +/- 5.3 ng/10(6) cells at 48 h of incubation. Moreover, ir-SmC/IGF 1 was also evidenced in SCCM following high performance liquid chromatography using a muC18 Bondapak column; ir-SmC/IGF 1 Sertoli cell-conditioned medium co-eluted with pure human SmC/IGF, suggesting a high homology between the two peptides. The effects of SmC/IGF 1 on testicular steroidogenesis were studied by incubating immature porcine Leydig cells with a biosynthetic human SmC/IGF 1. SmC/IGF 1 exerted a dose- and time-dependent stimulating effect on Leydig cell function with a maximal response at 50 ng/ml after 48 h of treatment. SmC/IGF 1 increased both LH/hCG binding (4.3-fold), basal testosterone (4-fold) and DHAS- and hCG-stimulated testosterone and DHAS (dehydroepiandrosterone sulfate) production (15.5- and 6.4-fold respectively). The slight effect of SmC/IGF 1 (100 ng for 48 h) on cell number (1.3-fold) and incorporation of [3H]thymidine into DNA (1.5-fold) in comparison with the high steroidogenic effect, supports the concept that SmC/IGF 1 acts as a cytodifferentiative factor rather than as a growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased urinary excretion of toxic hydrazino metabolites of isoniazid by slow acetylators. Effect of a slow-release preparation of isoniazid.

To test the hypothesis that slow acetylators, who may have a greater risk of developing isoniazid hepatitis than rapid acetylators, are exposed to more acetylhydrazine and hydrazine, two toxic metabolites of isoniazid, the urinary excretion of hydrazino metabolites of isoniazid was measured following the ingestion of 300 mg isoniazid. Slow acetylators (n = 7) excreted significantly more isoniazid (32.4 vs 9.2% dose), acetylhydrazine (3.1 vs 1.6% dose), and hydrazine (1.0 vs 0.4% dose) in 24 h than rapid acetylators (n = 5), whereas the excretion of acetylisoniazid and diacetylhydrazine was significantly lower. As the acetylation (i.e. detoxification) of acetylhydrazine is inhibited in the presence of high concentrations of isoniazid, a study was also made of the effect of a slow-release preparation that results in lower plasma concentrations of isoniazid on the production of hydrazino metabolites. The ratio of acetylisoniazid to isoniazid in urine was significantly increased in slow acetylators from 0.84 to 1.02 following administration of the slow release preparation, indicating increased acetylation of isoniazid. However, the excretion of diacetylhydrazine relative to the excretion of acetylhydrazine and hydrazine did not change. It is concluded that exposure to toxic metabolites of isoniazid is increased in slow acetylators. Detoxification of the toxic metabolites was not enhanced by a slow-release preparation of isoniazid.

Somatomedin C/insulin-like growth factor 1: an intratesticular differentiative factor of Leydig cells?

By using immature porcine Sertoli cells cultured in serum-free defined medium, we report that medium conditioned by Sertoli cells contained immunoreactive somatomedin C/insulin-like growth factor 1 (SmC/IGF1) measured following acidic gel filtration. The release of this immunoreactive SmC/IGF1 was slightly increased following Sertoli cell treatment with fibroblast growth factor but not with follicle-stimulating hormone or growth hormone. On the other hand, human biosynthetic SmC/IGF1 exerts a potent stimulatory effect on Leydig cell differentiated functions such as LH/hCG-binding (greater than 4-fold) and hCG-stimulated testosterone secretion (greater than 15-fold). This effect was dose and time dependent and the maximal increase of Leydig cell function was observed following 48 h treatment with 50 ng/ml SmC/IGF1. The steroidogenic action of the peptide was not related to Leydig cell growth since both cell number and 3H-thymidine incorporation into DNA were not or slightly (approximately equal to 1.5-fold) increased in the optimal conditions with SmC/IGF1 treatment (100 ng/ml for 48 h). Moreover, the concomitant treatment of Leydig cells by both arabinoside C (10(-5) M), a DNA synthesis inhibitor, and SmC/IGF1 did not modify the stimulating effect of the peptide on LH/hCG-binding and hCG-stimulated testosterone production. Taken together, the present findings support the concept that Sertoli cell derived SmC/IGF1 could be a potent regulator of Leydig cell differentiated functions.

Pattern of plasma levels of cortisol, dehydroepiandrosterone and pregnenolone sulphate in normal subjects and in patients with homozygous familial hypercholesterolaemia during ACTH infusion.

The aim of this study was to determine whether patients with homozygous familial hypercholesterolaemia (FH) have impaired adrenal cortical function. Plasma levels of cortisol, dehydroepiandrosterone (DHA), pregnenolone sulphate (PS) and DHA sulphate (DHAS) were measured during and 8 h ACTH infusion in six controls and two patients with homozygous FH. The basal PS levels of both patients and the basal DHA level of one were abnormally low for age and pubertal stage. During ACTH infusion we observed in both patients: (1) a mild impairment of control response after sustained stimulation (P less than 0.002); (2) a clear impairment of PS response (values less than 2 SD of those in controls); (3) a clear impairment of DHA response (values less than 2 SD) until 4 h in the boy who was at pubertal stage 4 and whose response could be compared to controls; no increase at all in the affected girl (pubertal stage 2) at a stage where normal subjects respond with significant increase. These results suggest that patients with FH lack cholesterol for corticosteroid biosynthesis under maximal ACTH stimulation and that mild chronic ACTH stimulation due to a deficit in the cholesterol supply to adrenal cells might increase the conversion of delta 5 to delta 4-steroids. They provide further evidence to support the primordial role of low density lipoprotein (LDL)-cholesterol in adrenal steroidogenesis in vivo.

Effect of concomitant isoniazid administration on determination of acetylator phenotype by sulphadimidine.

The influence of concomitant administration of isoniazid (INH) on the acetylation of sulphadimidine has been studied in 6 healthy volunteers, previously identified as having the fast acetylator phenotype. INH was administered in a slow release form (500 mg tablet) 1 hour before the sulphadimidine. Acetylation of sulphadimidine was measured in plasma 6 h after its intake and in urine collected between 5 and 6 hours. INH significantly decreased the acetylated fraction of sulphadimidine in plasma from 69.0 to 54.0 and in urine from 85.9 to 81.2%. This was reflected in a significantly higher plasma concentration of unconjugated sulphadimidine and reduced urinary excretion of acetylated sulphadimidine. It is concluded that concomitant administration of INH inhibits acetylation of sulphadimidine. Fast acetylators at the border line of discrimination, may be misclassified if phenotyped with sulphadimidine during concomitant administration of INH.