Some biochemical characteristics of hormone-secreting pituitary tumors and of the host's anterior pituitary gland

The activity of some glycolytic, oxidative, and degradative enzymes was studied in transplanted rat hormone-secreting pituitary tumors MtTW15 and 7315a and in the host pituitary gland. The elevated serum-hormone concentrations produced by 7315a tumor decreased the size of the host's pituitary gland, its hormone content, and G6P-DH, LDH, PK, and ICDH, but produced no changes in MDH, acid phosphatase, cathepsin-D, and LYSAR enzyme activities (mU/mg tissue). LDH and PK activities were greater in unit weight of pituitary tumors than in pituitary glands. Although more G6P-DH was found in MtTW15 tumor than in normal pituitary tissue, less of the enzyme was detected in 7315a pituitary tumor. It is concluded that elevated serum pituitary hormones selectively decrease hormone production and the activity of some enzymes in the pituitary gland, presumably through a feedback mechanism.

Three Types of Hereditary Antiterombin III Deficiency

The authors detected in the last seven years 15 patients with hereditary antithrombin III/AT III/ abnormality. All of them had typical clinical signs of recurrent arterious and venous thromboembolie. The abnormality inherited as an autosomal trait. Three types of the abnormality could be observed. In Type I both quantity and function of AT III were extremely decreased. In type II AT III is normal in quantity but abnormal in function. In Type III AT III is quantitatively normal and also its function seems normal as far as its basic activity is concerned /activity measured in absence of heparin/, but its abnormality becomes manifest in the presence of heparin in vitro/and also in vivo/. 5 of the patients belonged to Type I, 4 to Type II and 6 to Type III. In 60 examined family members of the 15 patients an abnormal AT III could be observed in 44, clinical signs in 23.

The examination of AT III activity in the presence of a given amount of heparin ia of great importance in recognition of the different types of antithrombin III abnormalities.

Activity alterations of metabolic enzymes in the anterior pituitary of female rats during acute and chronic starvation, as well as after refeeding

The activity of glycolysis and hexose monophosphate shunt decreases while the activity of some oxydative enzymes and acid phosphatase increases in the anterior pituitary of adult female rats during starvation. The alterations depend on the severity of starvation. The polypeptide hormone production also decreases. A close relationship exists between the metabolic activity of the gland and its endocrine function.

The role of estrogens in the regulation of lactate dehydrogenase activity and its submolecular organization in rat anterior pituitary

Estrogens increase LDH activity and decrease H/M subunit ratio in rat anterior pituitary in both the experimental circumstances and the physiological conditions. The cellular messengers mediating estrogenic effect are structure- and stereospecific. The activity increasing and subunit ratio decreasing potency of the three tested estrogens was of following decreasing order: 17 beta-estradiol, estrone, and estriol. 17 alpha-estradiol did not affect activity parameters and submolecular organisation of the enzyme. The estrogen induced activity increase is consequence of the enhanced de novo enzyme protein synthesis which could be inhibited by Actinomycin-D. The lack of adrenocorticoids did not involve the alteration of LDH activity and H/M ratio in female rat anterior pituitary. Accordingly, these steroids do not mediate estrogenic action. 17 beta-estradiol had a substantial increasing effect on LDH activity in the subrenal implanted pituitary homografts and decreased H/M subunit ratio. Pituitary LDH activity in androgenized female rats decreased only after the removal of the polycystic ovaries. The two latter observations suggest that hypothalamic hormones are not involved in the regulation of pituitary LDH activity and its submolecular organization. De novo synthesis of LDH enzyme protein and the regulation its submolecular organization is induced by the direct action on anterior pituitary cells of the estrogens.

Changes of lactic dehydrogenase activity and combination of its subunits in rat anterior pituitary during puberty and in maturity, as well as during estrous cycle on the actue effect of estradiol and after castration

LDH activity in the female rat anterior pituitary increases substantially at the opening of the vagina, after the gradual increase up to the 90st day no important change occurs. During the estrous cycle activity reaches its peak during the estrus, and lowest in ghe proestrus. Molecular organization of the enzyme shows a change only at the opening of the vagina, i. e. a sudden decrease of H/M ratio occurs, value of which does not change during the estrous cycle. Pituitary LDH activity and subunit ratio in males remains constant during life. LDH activity excess in mature female rat pituitary, being about the double as compared to males, develops at the age of about three months, the difference in H/M ratio however is manifest already during puberty. Anterior pituitary LDH activity and structure of the enzyme are affected by sexual hormones, primarily by estradiol, under physiological conditions, too. After ovariectomy LDH activity decreases gradually. The value before the opening of the vagina to be considered as basal level, develops in the 4th postoperative week. H/M ratio decreases by 20 per cent one week after the operation and shows no change thereafter. Orchidectomy involves but a minor activity and H/M ratio decrease. Experimental findings on activity and subunit ratio are related presumably to prolactin cells and suggest that sexual hormone feedback effects in addition to polypeptide production pituitary metabolism.

Sexual difference in pituitary pyruvic acid content, as well as of lactic acid/pyruvic acid quotient

The lactic acid/pyruvic acid quotient of rat anterior pituitary varies betweeen 30 and 80. The dominance of lactic acid is in accordance with the earlier observation that pituitary lactate dehydrogenase isoenzymes in rat are made up, in majority, of M subunits. The pituitary lactic acid concentration in female and male animals shows no appreciable difference and does not change 2 and 4 weeks after castration. In males the pituitary pyruvic acid concentration was almost double of that in females. Pyruvic acid content increases after ovariectomy and decreases after orchidectomy. The sexual differences having been observed in lactic acid/pyruvic acid quotient are in correlation with the discrepancy of pyruvic acid concentration.

Correlation between sexual steroid effect and activity changes and isoenzyme distribution of lactate dehydrogenase (EC 1.1.1.27) in rat anterior pituitary

Sexual steroid feed-back is a fundamental regulating factor oification of pituitary metabolism in rat. Oestrogen synthesis and/or activity of M subunif testosterone, in males testosterone treatment as well as lack of oestrogen result in characteristic pituitary LDH activity and isoenzyme distribution. Physiological doses of sexual steroids affect, directly or indirectly, pituitary LDH activity, oxydative metabolism, and imply different biochemical bases for the polypeptide hormone production in the anterior pituitary gland.

Growth hormone and prolactin content of hyperplastic anterior pituitary of dehydroepiandrosterone treated rats

30 days after implantation of 80 mg dehydroepiandrosterone (androst-5-en-3betaol-17-one) hyperplastic enlargement of the anterior pituitary has been observed in about 80 per cent of the female rats. There was an important increase of prolactin content, growth hormone content remained unchanged. The mentioned alterations were found to be reversible, since regression was observed after DEA treatment exceeding 30 days. In females developing no hyperplasia pituitary growth hormone contentration and content has been decreased, prolactin content remained unchanged. In male rats on identical treatment no change of pituitary weight, growth hormone and prolactin concent has been found. The results suggest that, under physiological conditions, DEA does not affect pituitary growth hormone and prolactin content, however response to pharmacological doses was different in male and female rats.

Compensatory hypertrophy in radiothyroidectomized dwarf rats

The aim of the study was to clarify whether growth hormone and thyroid hormones play a role in compensatory organ hypertrophy. Radiothyroidectomized dwarf rats with serious disorder of growth hormone production due to the loss of thyroid function were used in the experiments. As regards growth hormone production these animals may be considered as having been "hypophysectomized". The loss of thyroid function and growth hormone deficiency did not affect the degree of compensatory hypertrophy of the kidney, the adrenal and the gonad. The observation indicates that the hormones under study are not of decisive importance in the mechanism of compensatory organ enlargement. Further investigations are needed to clarify whether organ enlargement in the hypometabolic rat occurring at the level observed in the controls is associated with enhanced function.