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At least 19 recordsLinked to original sources
PubMed1993

Regulation of cholesterol metabolism in adrenal cortex: effects of apoproteins on cholesterol esterase in rat adrenal glands.

We have investigated the effects of apoproteins on cholesterol esterase (CEase) in rat adrenal glands in order to clarify the mechanism of synthesis of free cholesterol which is the most important substrate for steroidogenesis. We prepared lipid mixtures containing cholesteryl oleate plus apoproteins with and without phosphatidylcholine as a substrate for CEase in order to investigate the effect of the substrate state on CEase. The substrate containing only cholesteryl oleate and apo-HDL increased both acid and alkaline CEase activities. Both acid and alkaline CEase activities were also increased by a substrate containing apo-HDL plus cholesteryl oleate and phosphatidylcholine more than by a substrate containing cholesteryl oleate plus apo-LDL with phosphatidylcholine or cholesteryl oleate with phosphatidylcholine. We have already reported that phosphatidylcholine is an important factor for the regulation of adrenal CEase. Therefore, the present studies show that apoproteins as well as phosphatidylcholine may be important factors for the regulation of adrenal CEase.

Adrenal Cortex↗
PubMed1993

[Interrelationship of microsomal and mitochondrial systems for hydroxylating steroids from cattle adrenal cortex: effect of highly-purified components of the mitochondrial monoxygenase system on hydroxylation of steroids by microsomes].

The possibility of functioning of microsomal steroid hydroxylases in the adrenal cortex in the presence of the electron-transporting proteins in mitochondrial monooxygenase systems has been studied. It was found that adrenodoxin reductase stimulates both the 21- and 17 alpha-steroid hydroxylation activities in microsomes of the adrenal cortex with the same efficiency as does NADPH-dependent cytochrome P-450 reductase. Using cytochrome b5 and its specific antibody, an attempt has been made to investigate possible mechanisms of the stimulating effect of adrenodoxin reductase.

Adrenal Glands↗
PubMed1975

Quantitative ultrastructural study of the adrenal cortex: effects of a mammotropic pituitary tumor producing growth hormone and prolactin (MtT-W10), and of injected growth hormone in the rat.

The ultrastructure of the adrenal cortex has been examined in animals bearing a growth hormone and prolactin secreting mammotropic tumor (MtT-W 10). The large quantities of hormone secreted by the tumor caused a stimulation of zona fasciculata cells. The adrenal weight increased approximately 2-fold in tumor bearing animals. There were increases in the cellular volume of zona fasciculata cells and in the volume of mithchondria and smooth endoplasmic reticulum per cell as determined by quantitative morphometric techniques. The surface area of smooth endoplasmic reticulum and total mitochondrial membranes showed a significant increase in zona fasciculata cells as well. Injections of purified bovine growth hormone caused small but not significant increases in mitochondrial and smooth endoplasmic reticulum volumes. Growth hormone however did induce a significant increase in the surface area of mitochondrial membrane.

Adrenal Glands↗
PubMed1981

Regulation of the fetal human adrenal cortex: effects of adrenocorticotropin on growth and function of monolayer cultures of fetal and definitive zone cells.

Monolayer cultures have been prepared from both definitive and fetal zones of the human fetal adrenal cortex. Cultures from each zone consist predominately of adrenocortical cells, as determined by a specific morphological retraction response to ACTH, and by ACTH-induced inhibition of DNA synthesis and cell proliferation. Cell growth was stimulated by fibroblast growth factor. ACTH stimulated steroidogenesis in cells from each zone with an ED50 of 0.4--1.0 nM and at a maximal concentration of 5 nM. Short term stimulation of less than 24 h with ACTH produced a pattern of steroid secretion that was characteristic of the zone of origin. Definitive zone cultures produced both cortisol and dehydroepiandrosterone plus its sulfate (DHA/S), with cortisol production exceeding DHA/S production. Fetal zone cultures produced more DHA/S than cortisol. 3 beta-Hydroxysteroid dehydrogenase, delta 4,5-isomerase enzyme activity was 3-fold less in fetal than in definitive zone cultures. Long term stimulation of 1--4 days with ACTH, 8-bromo-cAMP, or cholera toxin increased steroidogenic capacity in cultures from both zones. The pattern of steroid production by definitive zone cells remained constant, but cortisol production was preferentially increased in fetal zone cells. Forty-eight-hour treatment of fetal zone cells with ACTH increased 3 beta-hydroxysteroid dehydrogenase, delta 4,5-isomerase activity 5-fold. alpha-, beta-, gamma 1-, gamma 2-, and gamma 3-MSH were not effective steroidogenic agents for either zone. These studies indicate that steroidogenic agents induce in fetal zone cells steroid production characteristic of definitive and adult adrenocortical cells.

Adrenal Cortex↗
PubMed1994

Basic fibroblast growth factor receptor in the rat adrenal cortex: effects of suramin and unilateral adrenalectomy on receptor numbers.

Previous studies have suggested that basic fibroblast growth factor (bFGF) is involved in the mediation of the compensatory adrenal growth response. These studies were undertaken to identify the bFGF receptor in the rat adrenal cortex and determine bFGF receptor levels in vivo. Initial studies using primary cultures of rat glomerulosa cells demonstrated a high affinity binding site with a Kd of 10 pM, consistent with reported values for the bFGF receptor; however, these results could not be demonstrated in capsule-glomerulosa tissue. Using autoradiography to verify the existence of bFGF receptors in vivo, heparin-insensitive [125I]bFGF-binding sites were concentrated primarily in the capsule and glomerulosa of the adrenal cortex, suggesting the presence of FGF receptors. The presence of bFGF receptors was further verified by demonstration of internalization of [125I]bFGF into cells of capsule-glomerulosa preps. This approach was used to demonstrate that suramin (a bFGF antagonist) pretreatment of rats results in bFGF receptor up-regulation in the adrenal cortex. In addition, we demonstrated a decrease in bFGF internalization in the remaining adrenal 24 h after unilateral adrenalectomy, suggesting the utilization of bFGF during the compensatory adrenal growth response. Together, these data support a role for bFGF in autocrine stimulation of the adrenal cortex and in the compensatory adrenal growth response.

Adrenal Cortex↗
PubMed1989

The kinetics of steroidogenesis activator polypeptide in the rat adrenal cortex. Effects of adrenocorticotropin, cyclic adenosine 3':5'-monophosphate, cycloheximide, and circadian rhythm.

The behavior of steroidogenesis activator polypeptide (SAP), a recently described modulator of cholesterol side-chain cleavage activity (Pedersen, R. C., and Brownie, A. C. (1987) Science 236, 188-190), was investigated in rat adrenocortical cells using a specific radioimmunoassay. In response to a maximal dose of adrenocorticotropic hormone (ACTH) (1 nM) or of 8-Br-cAMP (1 mM), an increase in intracellular SAP begins rapidly (less than 1 min) and reaches half-maximal and maximal levels (16-fold greater than basal) at 3 and 15 min, respectively. A plateau at this maximal concentration of SAP is then maintained. The levels of intracellular SAP content and of corticosterone output exhibit a similar dose-dependent response to ACTH (EC50 = 25 and 30 pM, respectively). Treatment of ACTH-stimulated cells with cycloheximide reverses the rise in SAP (t1/2 congruent to 5-7 min). In vivo the SAP content of adrenals from quiescent rats is concordant with the circadian rhythm of the pituitary-adrenal axis; at the apex (1800 h), adrenal SAP is 13-fold higher than at the nadir (0800 h), paralleling 2- and 7-fold variations in cholesterol side-chain cleavage activity and serum corticosterone levels, respectively. At both time points, SAP levels rise in response to stress. Of the rat tissues examined, only the major steroid-forming organs (adrenal cortex and gonads) had significant levels of immunoreactive, cAMP-responsive SAP, while cAMP-unresponsive immunoreactivity was also detectable in the thymus, spleen, and brain. Considered together with the biological activity previously demonstrated for SAP in vitro, these data are consistent with its role as a cAMP-dependent, cycloheximide-sensitive modulator of steroid biosynthesis.

8-Bromo Cyclic Adenosine Monophosphate↗