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Biomedical subjects

A S Mikosha

Publications and source records attributed to A S Mikosha.

At least 19 recordsLinked to original sources
PubMed2001

Isoforms of protein kinase C and their distribution in human adrenal cortex and tumors.

The cytosol and microsomal fractions of human adrenal cortex contain 3 isoforms of protein kinase C: alpha, zeta, and epsilon. The latter fraction is present in trace amounts. No isoforms beta1, beta2, gamma and delta were found in these cell fractions. The distribution of alpha-isoform between the cytosol and microsomal fraction is determined by tissue origin: in normal tissue its content differs by no more than 10%, while in most tumors this isoform is translocated into the microsomal fraction. The distribution of zeta-isoform did not depend on tissue origin.

Adrenal Cortex↗
PubMed1997

[Current problems of regulation of adrenocortical function].

The currently available data on the regulation of corticosteroid secretion are analyzed. ACTH is the main regulator during acute stress. It accelerates the biosynthesis of glucocorticoids at the stage of cholesterol delivery to the mitochondrial inner membrane where the latter is converted to pregnenolone by side-chain cleavage. The Steroidogenic Acute Regulatory Protein (STAR) could play a great role in the supply of mitochondria with cholesterol. Under chronic stress, adrenal hypertrophy is largely involved in higher corticosteroid formation. Neuropeptides, cytokines, and growth factors modulate adrenal function. Prolactin which plays a role as a mitogenic factor in many tissues takes an active part in the control of adrenal function and proliferation.

Adrenal Cortex↗
PubMed1996

[Phosphorylation of adrenal cortex proteins by protein kinase C induced by prolactin].

The in vitro effect of prolactin (PRL) on protein phosphorylation in male guinea pig adrenal cortex has been studied. It was found that 60 min after addition of PRL (10 micrograms/ml) to slices of adrenocortical tissue the rate of protein phosphorylation increased considerably. Autoradiographic studies revealed that at least part of the proteins are substrates for protein kinase C, since their phosphorylation increased in the presence of specific activators of protein kinase C (Ca2+, diacylglycerol, phosphatidyl serine) in the incubation medium. The molecular masses of these proteins were 95, 93, 90, 12 and 10 kDa. In extracts of PRL-treated adrenocortical tissue phosphorylation of these proteins was especially well-pronounced. Addition of staurosporine (10 nM) during incubation of the slices abolished the PRL effect on protein phosphorylation without any effect on the rate of unstimulated phosphorylation. Taking into account the ability of isolated nuclei to respond to PRL by activation of protein kinase C, the time course of PRL stimulation of protein phosphorylation was studied using preparations of isolated nuclei. The maximal increase of 32P incorporation into the proteins from [gamma-32P]ATP was observed after 60 min. Staurosporine only slightly attenuated the PRL effect.

Adrenal Cortex↗
PubMed1992

Trophic effect and modulation of ACTH-dependent stimulation of steroidogenesis by prolactin in guinea pig adrenal cortex.

The effect of PRL in intact guinea pig on the incorporation of specific labelled precursors into DNA, RNA, proteins and corticosteroids in adrenocortical tissue of intact guinea pig at different levels of activation of the gland were studied. PRL (2 IU/100 g daily) did not cause any significant changes until 3 days of treatment. PRL administered alone for 3 days caused significant elevation of 3H-thymidine incorporation into DNA in adrenocortical slices and no significant changes in labelling of RNA, protein and corticosteroids. In contrast, PRL administered together with ACTH (0.5 IU/100 g) for 3 days did not affect DNA synthesis but caused increase of 3H-cholesterol incorporation into cortisol and cortisone additionally to the ACTH action. Labelling of 17-deoxycorticosteroids in adrenocortical slices from animals of ACTH+PRL group either did not change significantly (aldosterone) or decreased (corticosterone).

Adrenal Cortex↗
PubMed1991

The participation of cAMP and protein kinase C in the regulation of aldosterone biosynthesis by potassium.

The mechanism of the effect of potassium ions (K+) on aldosterone production in guinea pig adrenal cortex was examined. At high K+ concentrations (approximately 8 mM) in the incubation media, aldosterone output and content was elevated, and there was a significant increase in the phosphorylation of intracellular proteins and of protein kinase C activity. Cyclic AMP levels showed a less significant increase. EGTA and lanthanum ions (La3+), and also chlorpromazine with regard to protein phosphorylation, appeared to remove the effect of raised K+ concentrations on steroidogenesis and protein phosphorylation. At low K+ concentrations, addition of EGTA led to a significant accumulation of cyclic AMP. Evidence that steroidogenesis is regulated by a cyclic-AMP-dependent mechanism at low K+ levels is presented, and we also report the first direct evidence of activation of aldosterone synthesis by protein kinase C at high K+ concentration.

Adrenal Cortex↗
PubMed1990

Effect of prolactin on phosphatidylcholine hydrolysis via phospholipase C in isolated adrenocortical cells of guinea pig.

Prolactin significantly increased the rate of incorporation of [3H]choline into phosphorylcholine (PRC) in a purified suspension of guinea pig adrenocortical cells. The rate of phosphatidylcholine (PTC) labelling and cellular PTC content did not change. In cells prelabelled with [3H]choline or CDP [14C]choline, prolactin diminished the rate of reduction of the radioactive PRC pool after 60-90 min incubation without any change in the rate of PTC biosynthesis. Taken together, these findings suggest that prolactin stimulates the hydrolysis of PTC by phospholipase C into PRC and diacylglycerol. The significance of this effect as part of the mechanism of action of prolactin on adrenocortical cells is discussed.

Adrenal Cortex↗
PubMed1989

[Role of cAMP in the regulation of adrenal mineralocorticoid function by potassium ions].

The role of cAMP in K+-dependent regulation of aldosterone output was studied. Guinea pig adrenal slices were incubated with various concentrations of K+ for 20 min. Aldosterone and cAMP output, protein synthesis and phosphorylation were increased with a rise in K+ concentration. The increase in the phosphorylation of the protein with apparent molecular weight of about 38 kD resulted from the increase in K+ concentration in the incubation medium. Proteins from adrenal slices preincubated with 3.0 and 11.0 mM K+ were separated by SDS polyacrylamide gel electrophoresis. No qualitative differences were revealed in autoradiograms of [14C]-prelabeled proteins; however, quantitative differences were present. These results suggest that the cAMP messenger system may be involved in the K+-dependent control of aldosterone biosynthesis.

Adrenal Glands↗
PubMed1989

[Receptor of prolactin and its effect on binding of corticotropin in human and guinea pig adrenocortical cells].

Specific binding of prolactin (PRL) by human and guinea pig isolated adrenocortical cells is saturable and reach equilibrium during 60 min. Characteristics of PRL binding by adrenocortical microsomes were determined. A single receptor species related to the high affinity and low binding capacity receptor class was revealed. The PRL-receptor affinities in adrenal cortex and liver are similar (approximately 10(9) M-1). Human adrenals have a higher affinity than that in guinea pigs. PRL increased corticotropin binding by adrenocortical cells of both species. Corticotropin binding rise may be due to the increase in the number of available receptors of low affinity and high capacity.

Adrenal Glands↗
PubMed1989

[Chloditan-induced changes in lipid peroxidation in the adrenals of dogs and guinea pigs].

The effect of adrenocorticolytic drug chloditan (1-(o-chlorophenyl)-1-(p-chlorophenyl)-2,2-dichloroethane;) on the content and the rate of lipid peroxidation in dog and guinea pig adrenals was studied. In adrenals of dogs and guinea the amount of malondialdehyde (MDA) was increased. In vitro spontaneous lipid peroxidation was delayed in adrenal homogenate of DDD-treated dogs. Spontaneous lipid peroxidation in adrenal homogenate was not decreased by feeding DDD in the guinea pig. DDD consumption did not affect on lipid peroxidation promoted by ascorbic acid and ferrous iron. The accumulation of MDA in dog and guinea pig adrenal homogenates was inhibited by NADPH.

Adrenal Glands↗
PubMed1987

[Effect of K+ concentration on the rate of synthesis of fast-labeling proteins in the adrenal cortex].

The effect of K+ concentration on protein biosynthesis and 32P-incorporation into the acid-insoluble fraction of dog and guinea pig adrenal cortex slices was studied. An increase in K+ concentration in the incubation medium from 3 to 8-11 mM induced after 15-20 min of incubation a significant stimulation of 14C-leucine incorporation into the acid-insoluble fraction of post-mitochondrial supernatant. More extensive labelling of this fraction with 32P was observed. Addition of valinomycin caused a shift in the maximum of 14C-leucine incorporation towards lower K+ concentrations. The Na+,K+-ATPase inhibitors--ouabain and strophantin K--reduced the K+-stimulated protein synthesis. These data suggest that K+ transport into the cell is necessary for the stimulating effect to be manifested. Chelation of Ca2+ strongly decreased the incorporation of 14C-leucine into proteins in the presence of 5 mM K+. However, protein labelling increased with a gradual rise in K+ concentration up to 25 mM.

Adrenal Cortex↗
PubMed1978

[Effect of O,N'=dichlorodiphenyldichloroethane and pertan in vitro on glutathione reductase activity in the adrenals of dogs and guinea pigs].

Glutathione reductase is activated by o,p'-dichlorodiphenyldichlorethane (o,p'-DDD) and pertan added in a concentration of 312 micrometer to the homogenate and cytoplasmic fraction of the dog adrenals. At a concentration of 156 micrometer o,p'-DDD and pertan failed to influence the glutathione reductase activity of the dog adrenal glands. Added in vitro, o,p'-DDD and pertan activate glutatione reductase of the quinea pig adrenal glands. O,p'-DDD does not affect the glutathione reductase activity of the liver and kidney cytoplasmic fraction in dogs. This observation confirms the high specificity of o,p'-DDD action on the adrenal glands.

Adrenal Glands↗
PubMed1975

Effect of o,p'-dichlorodiphenyldichloroethane on glutathione reductase activity and content of SH groups in the dog adrenals.

The effect of o, p'-dichlorodiphenyldichloroethane (DDD), a compound inducing atrophy of the adrenal cortex and blocking steroid production, on glutathione reductase activity was studied. As a result of feeding dogs with DDD in a dose of 50 mg/kg body weight for 14 days activation of glutathione reducatase took place in the homogenate, cytoplasmic fraction, and disintergrated mitochondria of the adrenals. On the additon of DDD in vitro the activity of the enzyme was unchanged. The content of SH groups expressed per 100 mg tissue was reduced in the homogenate and in all subcellular fractions. If expressed per 100 mg protein in the level of SH groups was lowered only in the microsomes and the disintergrated mitochondria.

Adrenal Glands↗