[Changes in the activity of adenylate- and guanylate cyclase in different rat tissues after chronic administration of ACTH or cortisol]. / Izmeneniia aktivnosti adenilat- i guanilattsiklazy v razlichnykh tkaniakh krys pri khronicheskom vvedenii AKTG ili kortizola.

The state of adenylate and guanylate cyclases in the adrenals, suprarenal fat and ventricular myocardium of the rat was studied under conditions of chronic administration of ACTH or cortisol. By the end of ACTH injections the weight of the adrenals and the DNA content in them increased 6 and 3 times, respectively; both parameters showed a gradual increase. The corticosteroid level in the blood changed throughout the experiment. The changes in the DNA content in the adrenals and in the corticosteroid level in the blood were oppositely directed. This was paralleled with cyclic changes in the basal and stimulated activities of adenylate and guanylate cyclases occurring with a periodicity of 15 days. The peaks of the cyclase activity preceded the increase in the DNA content. Similar cyclic changes in the enzyme activity were observed in the adipose tissue and myocardium. It was supposed that periodic changes in the cyclase activity are the main prerequisites for the growth and replication of cells under conditions of changed hormonal status of the organism.

[Dynamics of adenylate cyclase desensitization during long-term exposure to the hormone]. / Izuchenie dinamiki desensitizatsii adenilattsiklazy pri dlitel'nom deistvii gormona.

The dependence of adrenal gland adenylate cyclase desensitization on the dose of in vivo injected ACTH, the time of occurrence and duration of the enzyme refractory period and the dependence of desensitization on the number of ACTH injections were analyzed. The experiments were carried out on guinea pigs injected with prolonged action preparations of ACTH (4 and 6 units) daily for 1-6 days. Intramuscular injections of ACTH caused adenylate cyclase refraction to the repeated action of the hormone. The effect of desensitization was the most conspicuous within the first few hours after hormone injection. The decrease of adenylate cyclase sensitivity and the duration of this effect were found to depend on the ACTH dose as well as on the number of injections. It has been shown for the first time that a single in vivo injection of 0.9% NaCl causes short-term desensitization of adenylate cyclase to the repeated action of much higher doses of ACTH in vitro, presumably due to endogenous ACTH release in response to weak stress exposure. The periodicity of changes in adenylate cyclase sensitivity upon prolonged hormone administration is discussed. Sensitization of the enzyme upon daily short-term exposure to physiological doses of ACTH (administration of 0.9% NaCl for 6 days) was revealed.

[The role of periodic changes in cyclase and protein kinase activity in the mechanism of the proliferative effect of ACTH]. / Rol' periodicheskikh izmenenii aktivnosti tsiklaz i proteinkinaz v mekhanizme proliferativnogo deistviia AKTG.

A prolonged effect of ACTH on the state of adenylate and guanylate cyclase systems in the adrenal glands of experimental animals was investigated. It was found that in guinea pigs injected with ACTH (4 units daily for 1-50 days) the weight of adrenal glands and the DNA content in these organs increased 2.0-2.5-fold by the end of experiment; the increase in both values was stepwise. The corticosteroid level in the blood varied throughout the experiment: the changes in the DNA content in adrenals and in the corticosteroid content in the blood were oppositely directed. This was accompanied by cyclic changes in the basal and stimulated activities of adenylate and guanylate cyclases and proteinases in the adrenal glands occurring with a periodicity of 6-15 days. The activity peaks for cyclases and protein kinases preceded the rise in the DNA content in the adrenals. A clearcut correlation between the changes in the enzyme activity and the hormone dose was observed. The changes in the basal and stimulated activities of guanylate cyclase seem to be due to the control of cAMP level in the cell (stimulation of cGMP-dependent cAMP phosphodiesterase). Apparently, the periodic changes in the activity of cAMP-dependent protein kinases in the cytoplasmic and nuclear fractions and a relatively high activation of nuclear protein kinases (by 30-60%) in comparison of cytoplasmic ones (8-10%) are related to stimulation of DNA synthesis. It is concluded that the changes in the activity of cyclases and protein kinases play a role in the mechanism of proliferative effect of ACTH.

[Species and organ differences in the activity and regulation of adenylate and guanylate cyclases]. / Vidovye i organnye razlichiia v aktivnosti i reguliatsii adenilat- i guanilattsiklaz.

The activity of adenylate and guanylate cyclases was determined in adrenal, heart, liver and fat tissues of guinea pigs, mice, rabbits and monkeys. The enzymes activities varied markedly depending both on the species and organs. The highest basal activities of adenylate cyclase was observed in all organs of guinea pigs. It was found that organs with low basal level of adenylate cyclase possess high guanylate cyclase. Species variations of the basal and stimulated adenylate cyclase activity may determine the functional activity of an organ: the higher the adenylate cyclase activity, the more intensive steroidogenesis in adrenals, lipolysis in the fat tissue, muscle contraction and nerve impulse conduction in heart.

[Adenylate- and guanylate cyclase systems in pathology of the adrenal glands]. / Adenilat- i guanilattsiklaznye sistemy pri patologii nadpochechnikov.

The authors have summed up the results of a study of the activity of adenylate and guanylate cyclase system in the adrenals of patients with the Icenko-Cushing disease and syndrome and in the adrenals of experimental animals after unilateral adrenalectomy and in ACTH administration. It has been established that the biochemical mechanisms of compensatory hypertrophy of the adrenals in the normal and pathological tissue differ significantly. It has been shown for the first time that an increase in the basal activity of adenylate cyclase, resulting in the restoration of the initial hormonal level, is an obligatory condition for the compensation of organ function. Disorder in hormonal regulation of adenylate cyclase and diverse changes of the cyclase activity may indicate to the transition of tissue into a pathological state. Cyclic changes of the basal and stimulated activity of cyclases and protein kinases have been established for the first time in the adrenals of animals during administration of 2.5 units of ACTH for 5-40 days. The importance of detected changes in the mechanism of ACTH proliferative action is discussed.

[Adenylate cyclase and cAMP-dependent protein kinase activity in the adrenal glands of animals after chronic administration of ACTH]. / Izuchenie aktivnosti adenilattsiklazy i cAMP-zavisimykh proteinkinaz v nadpochechnikakh zhivotnykh pri khronicheskom vvedenii AKTG.

ACTH, a prolonged action hormone, in a dose of 2.5 mu. was injected into guinea pigs daily for 5-35 days. The adenylate cyclase activity of the crude adrenal membrane fraction and the activity of cAMP-dependent protein kinases in the cytoplasmic fraction were determined. Cyclic changes in the basal and stimulated adenylate cyclase activities occurring with 15-20-day intervals have been established for the first time. The sensitivity of adenylate cyclase to ACTH, NaF and GTP did not change in the course of two cycles. The activity of cAMP-dependent protein kinases increased during the first few days after ACTH administration and decreased after further injections of the hormone. The role of cyclic changes of the enzyme activity in the mechanism of proliferative effect of ACTH is discussed.

[Adenylate and guanylate cylase system function in human hyperplastic adrenals in Itsenko-Cushing disease]. / Sostoianie adenilat- i guanilattsiklaznoi sistem v giperplazirovannykh nadpochechnikakh cheloveka pri bolezni Itsenko-Kushinga.

The content of cyclic nucleotides and the activity of adenylate and guanylate cyclases as well as of cAMP phosphodiesterase in the human hyperplastic adrenals were determined after one- and two-step bilateral adrenalectomy for Itsenko-Cushing's disease. A decrease in cGMP concentration and a corresponding increase in cAMP/cGMP correlation were seen in the 2nd hyperplastic adrenal comparatively to those in the 1st one. An enhanced basal activity of adenylate cyclase and its lowered sensitivity to ACTH were found in the 1st and the 2nd adrenals. These changes correlate with a rise in the blood ACTH concentration in patients after the ablation of one adrenal. It is suggested that the augmented adenylate cyclase activity leads to an increased activation of steroidogenesis enzymes in the rest adrenal, ensuring the elevated rate of corticosteroid secretion. The nature of changes in guanylate cyclase activity is contrary to that of adenylate cyclase; namely, guanylate cyclase basal activity of the 2nd hyperplastic adrenal was shown to be lower than that of the 1st one. The cAMP phosphodiesterase activity in the 1st and the 2nd adrenals remained unchanged.

[Changes in cyclic nucleotide metabolism in compensatory adrenal hypertrophy (following unilateral adrenalectomy)]. / Izmeneniia v metabolizme tsiklicheskikh nukleotidov pri kompensatornoi gipertrofii nadpochechnikov (posle odnostoronnei adrenaléktomii).

The cyclic nucleotide content, adrenocortical adenylatecyclase, guanylatecyclase, cAMP and cGMP phosphodiesterase activity, as well as the blood corticosteroid content of guinea pigs were determined at the different periods after bilateral adrenalectomy. The raised basal adenylatecyclase effect was also seen during compensatory hypertrophy of the sole adrenal. The response of adenylatecyclase to ACTH and Na is also enhanced at this moment. It is suggested that a physiological increase in the blood ACTH concentration, resultant of unilateral adrenalectomy, intensifies the adenylatecyclase catalytic activity and does not induce enzyme desensitization. The guanylatecyclase activity grows. It was established that changes in both cyclase activities are dependent on the postoperative time and are equal by character. The alteration of adenylatecyclase state always leads to the rise of guanylatecyclase activity. Changes in the cAMP and cGMP phosphodiesterase activity were not observed.

[Adenylate cyclase activity and cyclic nucleotide content in human adrenal tumors under Icenko-Cushing syndrome]. / Aktivnost' adenilattsiklazy i soderzhanie tsiklicheskikh nukleotidov v opukholiakh nadpochechnikov cheloveka pri sindrome Itsenko--Kushinga.

The adenylate cyclase activity and cyclic nucleotide content in excised human adrenal tumours (Icenko-Cushing syndrome) were determined. The experimental data were compared to those obtained for hyperplastic adrenals. All adrenal tumours under study revealed a decreased cAMP level, an increased cGMP level and a resulting decrease of the cAMP/cGMP ratio. In malignant adrenal tumours the adenylate cyclase activity was sharply increased in comparison with that in hyperplastic adrenals. In the majority of malignant tumours the adenylate cyclase response to ACTH was either altogether absent or sharply decreased. In benign adrenal tumours the basal activity of the enzyme was unchanged and the enzyme response to ACTH was essentially normal. The decrease of adenylate cyclase response to ACTH in malignant tumours is apparently not due to the impaired catalytic activity of the enzyme, since its response to stimulation by sodium fluoride remains unaffected. In some tumours (one malignant and two benign ones) a non-specific stimulation of adenylate cyclase by hormones, which are not natural activators of the enzyme was observed. It was assumed that these changes are due to the damage of hormonal receptors in adrenal tumours.

[Paths of corticosteroid biosynthesis in the adrenal glands of rhesus monkeys]. / Puti biosinteza kortikosteroidov v nadpochechnikakh Macaca rhesus.

In experiments in vitro corticosteroid formation from radioactive cholesterol in tha adrenal glands of monkeys (Macaca rhesus) was studied. A conclusion was drawn that pregnenolone and its hydroxy-derivatives were of the leading significance in the cortizol and corticosterone synthesis in the adrenal glands of monkeys. Progesteron was produced in insignificant amounts and was almost unutilized for steroidogenesis. The formation of 17.21-dioxypregnenolone was revealed; its role in the capacity of cortizol precursor was proved; 17-oryprogesteron was found to be of no great significance in cortizol synthesis; 21-oxypregnenolone, but not progesteron proved to serve as the principal intermediate product in corticosterone formation.

[Pathways of corticosteroid biosynthesis in human adrenals (Itsenko-Cushing disease)]. / Puti biosinteza kortikosteroidov v nadpochechnikakh cheloveka (bolezn' Itsenko--Kushinga)

Pregnenolone and its hydroxyl derivatives are of dominant importance in cortisol and corticosterone synthesis in human adrenals (hyperplasic glands and adenomes) removed in Itsenko-Kushing disease. Progesterone is produced in minimal amounts and is nearly not used for steroidogenesis. Participation of 17,21-dihydroxypregnenolone in cortisol synthesis is demonstrated. 17-hydroxyprogesterone is found not to take an important part as cortisol precursor. 21-hydroxypregnenolone is an essential intermediate in corticosterone synthesis. 11-hydroxyprogesterone does not participate in corticosteroids formation, since the rate of progesterone 11-hydroxylation in human adrenal mitochondria is minimal.

Role of 11 beta-hydroxyprogesterone in biosynthesis of corticosterone from progesterone in guinea pig adrenals.

Slices of male guinea pig adrenals were incubated with trace amount of 3-H7 alpha-progesterone and the percentage of incorporation of 3-H into various steroids at various intervals was measured. It was found that 3-H accumulates predominately in 11 beta-hydroxyprogesterone as compared to DOC. This indicates that, in guinea pig adrenals, 11 beta-hydroxyprogesterone plays a dominant role in a formation of corticosterone from progesterone. The observed sequence of changes in progesterone label accumulation in 17-hydroxycompounds indicates they pathway of cortisol synthesis through the intermediate formation of 17-hydroxyprogesterone and 11-deoxycortisol.