ACTH-secreting Pituitary Tumors Research Articles

LH-RH and dopamine levels in hypophysial stalk plasma and their relationship to plasma gonadotrophins and prolactin levels in male rats bearing a prolactin- and adrenocorticotrophin-secreting pituitary tumor.

The present study was concerned with the effects of a transplantable pituitary tumor secreting prolactin (PRL) and adrenocorticotrophin (ACTH) on the levels of LH and FSH in peripheral plasma and on the hypothalamic release of LH-RH and dopamine in the male rat. Male rats of the same age not inoculated with the tumor served as controls. Hypophysial stalk blood was collected from urethane-anesthetized rats 4-5 weeks after tumor inoculation to measure their LH-RH and dopamine content. A peripheral blood sample was withdrawn from the animals just before sectioning the hypophysial stalk to measure their content of LH, FSH and PRL. It was found that in the tumor-bearing rats the levels of PRL increased 17-fold, whereas plasma levels of LH and FSH decreased by 45 and 70% respectively, when compared with the control rats. In the tumor-bearing rats, the secretion rate of dopamine in hypophysial stalk plasma increased from 1.4 to 4.1 ng/h, whereas the secretion rate of LH-RH decreased from 122 to 61 pg/h. However, when at the time of tumor inoculation adrenalectomy was performed, the tumor did not decrease plasma levels of LH and FSH and the secretion of LH-RH into hypophysial stalk blood any longer. The effect of the tumor on hypothalamic dopamine secretion was, however, still present in the adrenalectomized rats. It is concluded that the effect of the PRL- and ACTH-secreting pituitary tumor on plasma levels of LH and FSH requires the presence of the adrenal gland and that this effect is mediated through an inhibition of the hypothalamic release of LH-RH. Furthermore, this tumor increases the hypothalamic release of dopamine independent of the presence of the adrenal gland.

Transplantation of ACTH-secreting pituitary tumor cells in athymic nude mice.

Chronic excess of glucocorticoids results in Cushing's syndrome in humans. A common cause of excess cortisol secretion is the presence of an adrenocorticotropin secreting pituitary tumor which stimulates the adrenal cortex to produce excess glucocorticoids. ACTH-secreting AtT-20 mouse pituitary cells transplanted subcutaneously in oestrogenized athymic nude mice form tumors rapidly. Six weeks after receiving the tumor transplants, the mice weighed 45% more than normal mice due to the increase in body fat. The tumor-bearing mice exhibit the familial "buffalo hump" appeaance due to the abnormal distribution of body fat. The adrenal glands of the tumor-bearing animals are enlarged due to hypertrophy of the zona fasciculata. The foamy looking fasciculata cells in normal mice were converted to dense, eosinophilic cells in the tumor-bearing mice. Transplantation of normal pituitary glands to athymic nude mice with or without oestrogen treatment did not produce these morphological changes. The experimental model described here may be useful for future studies of Cushing's syndrome.

A cyproheptadine-reversible defect in ACTH control persisting after removal of the pituitary tumor in Cushing's disease.

We studied two phases of cortisol feedback suppression of ACTH in nine patients who had had adrenalectomy for Cushing's disease. Four had been treated by adrenalectomy alone and presumably had ACTH-secreting pituitary tumors. Five others were studied two or more years after transsphenoidal removal of an ACTH-secreting microadenoma. In both groups, cortisol-ACTH feedback during the first 30 minutes of cortisol infusion was abnormal; plasma ACTH fell only 2.7 +/- 2.6 per cent (mean +/- S.E.), as compared with 28.0 +/0 10.1 per cent in five hypoadrenal controls (p less than 0.01). The fall in ACTH during the second phase of cortisol infusion was similar in the patients and the controls. Cyproheptadine corrected the feedback abnormality occurring during the first phase in both groups of patients with Cushing's disease; ACTH fell by 24.4 +/- 4.8 per cent (P less than 0.005). Persistence of a cortisol-ACTH feedback abnormally after removal of the pituitary tumor in Cushing's disease, as well as the correction by cyproheptadine, suggests that higher centers have a role in the pathophysiology of Cushing's disease.

Circadian Cortisol Secretory Rhythms in Cushing's Disease*

Plasma cortisol was measured at 20-min intervals for 24 h in eight patients with Cushing's disease and ACTH-secreting pituitary tumors. The 24-h mean (+/- SD) cortisol level was 25.6 +/- 11.3 microgram/dl (range, 15.5--40.6), which was significantly higher than the level of normal control subjects (P less than 0.01). The 24-h mean ACTH level varied between 22--107 pg/ml, with a mean +/- SD of 63.4 +/- 27.2. The mean ACTH level was higher than that of the control subjects but the difference was not statistically significant. The 24-h cortisol secretory pattern was characterized by an absence of the normal circadian variation and a failure of the plasma cortisol level to fall to less than 2 microgram/dl between 2300--0300 h. The coefficient of variation, an expression of the amplitude of cortisol secretory episodes, was significantly decreased in patients with Cushing's disease compared to normal control subjects; there was no significant difference in the number of cortisol secretory episodes in the patients vs. control subjects. Three of the patients were restudied after successful resection of their ACTH-secreting pituitary tumors. Two showed normalization of their 24-h circadian cortisol patterns and normal metyrapone responses. In the third, the 24-h mean cortisol level was normal, but the circadian cortisol rhythm remained abnormal. This patient had diminished ACTH reserve, demonstrated by a subnormal response to metyrapone. Additional studies will be required to determine if normalization of the circadian cortisol rhythm occurs in all patients with Cushing's disease who are cured after transsphenoidal microsurgery and who also show normal ACTH reserve.

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A biosynthetic labeled peptide structurally related to the thymic peptide ubiquitin was first identified fortuitously in bovine pars intermedia cells in regard to its partial NH2 terminal amino acid sequence (Met 1, Leu 8, 15 and Lys 6, 11, 27, 29, 33) after a protein segment data bank search. A peptide with the same behavior on carboxymethylcellulose chromatography and polyacrylamide gel electrophoresis has been purified after labeling experiments in two areas of rat brain, hypothalamus and striatum, and in a mouse and a human ACTH-secreting pituitary tumors. It represents about 1 to 10% of the total labeled proteins in the various experiments. Its identity with the above mentioned bovine pituitary peptide was confirmed by microsequence analysis with respect to Met 1, Lys 6, 11 in hypothalmus, Met 1 in striatum, and Lys 6, 11, 27, 29, 33 in the two pituitary tumors. The availability of standard purified ubiquitin allowed us to show that labeled and cold peptides have the same electrophoretic mobility and elution volume on Sephadex G-50 chromatography this further confirms their identity. Possible interests of such a biosynthetic characterization of a ubiquitin-related peptide are discussed, particularly in view of the structural relationship of ubiquitin to the non histone component of nuclear protein A-24, and as a test of tissue viability and biosynthetic efficiency in our in vitro biosynthetic systems.

Biosynthesis of a ubiouitin-related peptide in rat brain and in human and mouse pituitary tumors

A biosynthetic labeled peptide structurally related to the thymic peptide ubiquitin was first identified fortuitously in bovine pars intermedia cells in regard to its partial NH 2 terminal amino acid sequence (Met 1, Leu 8, 15 and Lys 6, 11, 27, 29, 33) after a protein segment data bank search. A peptide with the same behavior on carboxymethylcellulose chromatography and polyacrylamide gel electrophoresis has been purified after labeling experiments in two areas of rat brain, hypothalamus and striatum, and in a mouse and a human ACTH-secreting pituitary tumors. It represents about 1 to 10% of the total labeled proteins in the various experiments. Its identity with the above mentioned bovine pituitary peptide was confirmed by microsequence analysis with respect to Met 1, Lys 6, 11 in hypothalmus, Met 1 in striatum, and Lys 6, 11, 27, 29, 33 in the two pituitary tumors. The availability of standard purified ubiquitin allowed us to show that labeled and cold peptides have the same electrophoretic mobility and elution volume on Sephadex G-50 chromatography this further confirms their identity. Possible interests of such a biosynthetic characterization of a ubiquitin-related peptide are discussed, particularly in view of the structural relationship of ubiquitin to the non histone component of nuclear protein A-24, and as a test of tissue viability and biosynthetic efficiency in our in vitro biosynthetic systems.

A POSSIBLE ACTH SECRETING TUMOUR OF THE PITUITARY DEVELOPING IN A CONVENTIONALLY TREATED CASE OF ADDISON'S DISEASE

A patient with Addison's disease, treated with conventional corticosteroid therapy, developed endocrine and radiological features suggestive of an ACTH secreting pituitary tumour. The negative feedback control of ACTH secretion by the inhibitory effect of hydrocortisone was shown to be preserved although attenuated. Retiming and alteration of corticosteroid therapy reinforced this feedback control, without the need for supraphysiological amounts of steroid, and resulted in the regression of the endocrine disorder.

Cellular injury of adrenocorticotropic pituitary tumor (AtT-20) by corticosteroid in mice.

A transplantable ACTH-secreting pituitary tumor (AtT-20) in mice was studied for its growth in relation to adrenocortical steroid. The latency of transplanted tumor in LAF-1 mice with 10(6) tumor cells was about 2 weeks in adrenalectomized and in intact mice. In the former, however, tumor size reached 1.5 cm in diameter within 1 month, while it remained about 0.5 cm in the latter. Macroscopic and microscopic observation revealed that the tumor grafted in intact mice showed massive necrosis, leaving minimum intact tumor cells among necrotic foci. In contrast, the tumor grafted in adrenalectomized mice was healthy, soft, and showed adenomatous structure. It is concluded that excess of adrenocortical steroid produced in the grafted AtT-20 was inhibitory for the growth of transplanted tumor and removal of the adrenal glands was good for growth and survival of transplanted tumor. For the assessment of direct effect of adrenal steroid on AtT-20 cells, incorporation of 3H-thymidine in cultured AtT-20 cells was examined in a medium supplemented with glucocorticoid hormone. The autoradiographic study indicated that the inhibition of 3H-thymidine uptake was demonstrated at 24 hr after incubation with steroid and labeled cells were barely detectable on 3rd and 5th day.

Rapid Appearance of Transient Secondary Adrenocortical Insufficiency After Alpha-Particle Radiation Therapy for Cushing's Disease

A 17-year-old women received 12,000 rads of alpha-particle radiation for the treatment of Cushing's disease. One day after the completion of therapy, the patient developed nausea, vomiting, headache, and postural hypotension. Laboratory evaluation demonstrated a marked fall of the previously elevated urinary 17-hydroxycorticosteroids (17-OHCS) and undetectable plasma cortisols. The urinary 17-OHCS transiently returned to supranormal levels but over a 2 1/2-week period decreased and then remained low. The patient also demonstrated a subnormal urinary aldosterone excretion in relation to plasma renin activity (PRA) during 10 mEq/24 h sodium restriction. The remainder of the endocrine evaluation was normal, suggesting that pituitary function otherwise remained intact. One and one-half years after alpha-particle therapy, the patients's urinary 17-OHCS were normal and responded normally to metyrapone. The relationship between urinary aldosterone excretion and PRA also was normal. It is postulated that there was an infarction of an ACTH secreting pituitary tumor leaving the remainder of the pituitary intact. Achronically elevated circulating level of ACTH with sudden loss of ACTH secretion appeared to have been responsible for the initial low urinary aldosterone as well as the low urinary 17-OHCS. This is the first reported case of a presumed pituitary tumor infarction in association with alpha-particle pituitary radiation.

EFFECT OF BROMOCRIPTINE IN PITUITARY-DEPENDENT CUSHING'S SYNDROME

Department of Medicine III and Clinical Endocrinology, University Hospital 'Dijkzigt', Erasmus University, Rotterdam, The Netherlands (Received 16 February 1976) The role of catecholamines in modulating the secretion of adrenocorticotrophin (ACTH) has been investigated by numerous workers with conflicting results (van Loon, 1973). In some of these studies l-DOPA has been used, which induces the production of adrenaline and noradrenaline in addition to that of dopamine. Recently 2-bromo-α-ergocryptine became available; this drug seems to be a more specific activator of the dopaminergic pathways in the central nervous system (Corrodi, Fuxe, Hökfelt, Lidbrink & Ungerstedt, 1973). On the basis of a recent observation, that the daily administration of 0·05 mg ergotamine to rats bearing ACTH-secreting pituitary tumours inhibited tumour growth and reversed adrenal enlargement (Macleod & Lehmeyer, 1973), we investigated the effect of bromocriptine on plasma ACTH levels in seven patients with pituitary-dependent Cushing's syndrome (one with a pituitary tumour) and four

Mitochondrial 11 β hydroxylation and adrenal morphology in rats bearing a mammotropic, ACTH-secreting pituitary tumor

The function and structure of adrenal mitochondria has been studied in rats bearing an ACTH, growth hormone and prolactin secreting tumor (MtT-F4). Basal levels of 11 β hydroxylation of deoxycorticosterone (DOC) in incubated mitochondria were higher in MtT-F4 than in controls ( P < 0.001). The addition of NADH and calcium to controls increased the conversion of DOC to corticosterone ( P < 0.001) but no change was observed in MtT-F4. With addition of NADPH plus calcium, the increase in controls was of a much higher magnitude than that produced in MtT-F4 ( P < 0.05). Calcium alone diminished the high levels of hydroxylation in MtT-F4. Measurement of mitochondrial swelling showed that in the presence of albumin and at 37°C swelling rates in MtT-F4 and controls were similar; however, large amplitude swelling developed in MtT-F4 when albumin was omitted and temperature was lowered to 25°C. ATPase activity was not different in mitochondria from both groups of rats either in the presence or absence of magnesium. The depressive effect of calcium, an uncoupler of oxidative phosphorylation, showed that some form of energy was needed for the high rate of basal hydroxylation in MtT-F4. The diminished response to the nucleotides indicated that probably both the P 450 hydroxylation chain and the transhydrogenase enzyme are impaired in MtT-F4. Electron microscopy of whole adrenal cortex showed a general appearance of hyperfunction. Mitochondria of zona glomerulosa contained inclusions of high electron density, and the outer membrane showed a multillaminar appearance. In zona fasciculata mitochondria showed normal structure, but different electronic density and individual variation in the number of cristae. In contrast, mitochondria of zona reticularis showed normal morphology.

BEHAVIOR OF HEPATIC GLUCONEOGENIC ENZYMES, RNA METABOLISM AND AMINO ACID LEVEL IN RATS CARRYING TRANSPLANTABLE ACTH-SECRETING PITUITARY TUMORS.

The metabolic effects of an ACTH-secreting transplantable mammotropic pituitary tumor, strain MtT.F4, were investigated in the rat. The body weight of the rats was not increased, but the liver weight and liver to body weight ratio were increased more than 2-fold and the adrenal weight was enlarged to 6 times that of normal rats. The activities of the hepatic enzymes involved in gluconeogenesis, glucose 6-phosphatase, fructose 1,6-diphosphatase, lactic dehydrogenase, and those of the malic enzyme and malic dehydrogenase were markedly increased. The liver homogenate and supernatant nitrogen, the free amino acid nitrogen content and the glycogen level increased approximately 2- fold. The amount of RNA was elevated 3- fold, whereas the incorporation of orotate into RNA decreased to one third the activity found in control, normal rats. V\fhen the animals bearing the ACTH-secreting pituitary tumors were adrenalectomized, the inci'eased enzyme activities, nitrogen, glycogen and RNA content decreased markedly. However, some of the parameters did not return completely to normal. The enzymatic and metabolic alterations in the liver of the ACTHproducing tumor-bearing host are attributed to increased adrenocortical hormone secretion. The changes are similar to those found in rats treated with exogenous adrenocortical hormones. (Endocrinology76: 902, 1965)

Vasopressin and ACTH release.

SummaryA new method of testing for ACTH-releasing activity of neurohumoral substances has been described. The material to be tested is injected directly into the arterial blood supply of an ACTH-secreting pituitary tumor grafted in the hind leg of a hypophysectomized rat. The amount of ACTH released is measured by the difference in corti-costerone secretion rate before and after the injection. Amounts of vasopressin as minute as 1.0 μU to 10.0 μU release measurable quantities of ACTH. Doses of vasopressin 1,500 times this amount given intravenously have no effect on ACTH release. These findings suggest that vasopressin may be the ACTH-releasing neurohumor. It is suggested that the method may be used as an assay method for vasopressin.

Growth of human epidermoid carcinomas (strains KB and HeLa) in hamsters from tissue culture inocula.

Summary1. The KB and HeLa strains of human epidermoid carcinoma have been established in the cheek pouches of golden hamsters by means of quantitated suspensions prepared from tissue cultures in a medium providing the specific amino acid and vitamin requirements of these cell lines. 2. Strain KB, isolated directly from a biopsy specimen in these media, has been grown in LAFi mice bearing homologous ACTH secreting pituitary tumors. This strain also has been established in the cheek pouch of non-conditioned hamsters but thus far has failed to grow in non-conditioned mice. 3. The use of quantitated tissue culture inocula for the production of tumors in the hamster cheek pouch for chemotherapeutic studies is suggested.