Medroxyprogesterone induced changes in rat liver. A light and electron microscopic study

Medroxyprogesterone acetate (MPA) induced morphological alterations in the normal female rat liver and after carbon tetrachloride exposure were assessed by light and electron microscopy and morphometry. Administration of MPA increased the smooth endoplasmic reticulum (SER) in normal rat. Carbon tetrachloride, injected intraperitoneally for four weeks, caused fatty accumulation, enlargement of the cell nucleus and decrease of the rough endoplasmic reticulum (RER) and increase of the SER. After one week of recovery, without treatment, the fatty infiltration and the SER membranes decreased and the RER increased. MPA, following injury, induced a decrease in the fatty accumulation and mitochondrial volume density and the hepatocyte nuclear and cytoplasm size normalized. The SER membrane volume density increased and the surface density decreased, the RER membrane volume density increased while the surface density did not alter significantly. The volume densities of the mitochondria and the peroxisomes decreased in the MPA treated CCl4 exposed groups. The results demonstrate that MPA induces a proliferation of the SER in normal rat liver and after hepatic injury the compound has a beneficial effect on the regeneration.     

Rapid alterations induced by insulin in hepatocyte ultrastructure and glycogen levels

The speed with which insulin alters hepatocyte ultrastructure and glycogen levels in insulin-deficient rats has been studied. Insulin deficiency was induced with alloxan, followed by insulin treatment with regular and NPH insulin. Rats were killed at various times after the insulin injection, blood samples were obtained, plasma glucose levels were determined, and liver samples were prepared for electron microscopy and glycogen determinations. Plasma glucose levels in insulin-deficient rats declined to normal values by 4 hours post insulin, returning to insulin-deficient levels by 8 hours post insulin. Hepatic glycogen was considerably reduced in the insulin-deficient rats. By 1 hour post insulin hepatic glycogen increased, reached maximal levels by 8 hours, then declined to insulin-deficient levels by 36 hours. The ultrastructural appearance of both centrilobular and periportal hepatocytes from insulin-deficient rats showed abundant vesicular smooth endoplasmic reticulum (SER), decreased rough endoplasmic reticulum (RER), and enlarged RER intracisternal spaces. One-half hour post insulin, centrilobular hepatocytes were unchanged. In periportal hepatocytes, however, vesicular SER was no longer visible, the RER intracisternal spaces appeared normal, and the amount of RER had increased. By 1 hour post insulin the centrilobular hepatocytes showed similar ultrastructural changes. These changes became more pronounced in the next few hours and remained through 24 hours. By 36 hours both centrilobular and periportal hepatocytes appeared similar to those in the insulin-deficient rat. These results demonstrate the rapid and lobular-specific effects insulin has on the hepatocyte.     

The fructose induces "glycogenosis". III. Histochemical and morphometrical studies of glycogen metabolism in mouse liver after fructose overload (author's transl)]

Introduction: After feeding fructose for 7 days rat liver cells show an accumulation of glycogen, a high activity of glucose-6-phosphatase combined with a SER- and RER-reduction. This result was reviewed by mouse liver cells using histochemical and morphometrical methods. Material and Methods: 60% fructose in drinking water was given mice as only nutritional source. Controls had free access to Altromin-R-standard diet and drinking water. Glycogen and glycogen metabolizing enzymes are demonstrated in the course of an 1-14 days fructose diet. After a 7 days diet liver tissue was analysed morphometrically. Results and discussion: Feeding of fructose leads to a high glycogen content, combined with a high activity of glycogen-phosphorylase and glucose-6-phosphatase in the liver parenchyma of mouse. Glycogen-synthetase activity falls to a low level. The SER and RER and the peroxisomes are reduced. The single volume of the hepatic nucleus is decreased and the hepatocellular chondrioma is transformed in a smaller number of larger mitochondria. Compared with the rate the analysed organelles and enzymes of mouse liver show only slight quantitative differences. The increase of glucose-6-phosphatase and simultaneous reduction of endoplasmic reticulum-membranes is illustrated by the dynamic structure of endoplasmic reticulum-membranes, which adapt to metabolic changes. The variable turnover of different parts of endoplasmic reticulum-membranes seems to be very important.     

Glycogen metabolism in cultured chick hepatocytes: A morphological study

Ultrastructural and autoradiographic observations of cultured chick hepatocytes under the following conditins are described: Induction of glycogen synthesis with glucose alone and glucose plus insulin, and glucagon-induced glucogen glucogen breakdown. Profiles of hepatocytes cultured in medium containig 10 mM glucose showed typical cellular organelles and occasionally a few glycogen granules. After incubation of hepatocytes with ³H-glucose, silver grains were found over these sparse glycogen granules, indicating a low level of glycogen synthesis by a few cells. After addition of 75 mM glucose for 1 hr about 3% of the profiles of cells showed glycogen, and by 24 hr half of the hepatocytes had glycogen. Addition ofinsulin plus glucose induced glycogen synthesis in 82% of the cells after 6 hr. and by 24 hr almost every cellular profile showed glyocgen particles. Morphologically, glycogen accumulation was similar whether the cells were stimulated by high glucose or by glucose plus insulin: glycogen granules appeared in restricted regions of the cytoplasm, which were rich in smooth endoplasmic reticulum (SER), and peroxisomes were found close to the newly deposited glycogen particles. At maximum glycogen accumulation the association of SER and peroxisomes with glycogen was less obvious. Glycogenolysis induced by incubation of glycogen-rich hepatocytes with glucagon resulted in proliferation of SER in the glycogen regions of the cells. These observations are compatible with the concept of regions in the hepatocyte cytoplasm specialized for glycogen metabolism. Possible roles for SER and peroxisomes found near glycogen particles and other organelles in hepatic glycogen metabolism are discussed.     

Action of metabolic hormones on the fine structure of rat liver cells III. Effects of adrenalectomy and administration of cortisone

Electron microscopic studies were made of hepatocytes from sham-operated rats, adrenalectomized animals fasted 15 hours, and adrenalectomized rats fasted 15 hours but given a single I.P. injection (10 mg) of cortisone acetate. The objective of this work was to define the earliest morphological response of hepatocytes to injection of a glucocorticoid and to provide additional information on the mechanism of hormone action at the cellular level. Hepatocytes from fasted, adrenalectomized rats contained no glycogen particles and very little smooth endoplasmic reticulum (SER). In addition the rough endoplasmic reticulum was disorganized and showed fewer ribosomes and polysomes than found in liver cells from sham-operated rats. Two hours after glucocorticoid injection glycogen particles were seen in numerous centrilobular cells and some periportal hepatocytes. Elements of SER were associated with the glycogen particles. By 4 hours after hormone injection abundant glycogen was found in all hepatocytes. Centrilobular cells showed dispersed glycogen with extensive tubules of SER associated with the glycogen particles. Periportal hepatocytes accumulated glycogen as dense masses scattered throughout the cytosome. SER occurred mainly at the edges of the glycogen masses. Midlobular cells showed glycogen patterns intermediate between periportal and centrilobular cells; masses of dispersed glycogen with abundant SER occurred within and around the glycogen areas of the cells. Glucocorticoid stimulation also caused cisternae of RER to align in parallel arrays, and more ribosomes and polysomes appeared on membranes of RER than in similar cells from adrenalectomized rats. The interpretation is offered that the glucocorticoid-stimulated proliferation of SER is the morphological expression of induced microsomal enzyme synthesis (glucose-6-phosphatase) known to occur under these hormonal conditions.     

Acute toxic effects of paraquat on ultrastructure of rat liver

Paraquat was administrated to pathogen-free male rats orally, and the livers were studied by light and electron microscope at intervals of 6 hours to 5 days. Congestion and hepatocellular injury (degeneration and/or fatty metamorphosis) were seen by light microscope. Electron microscope showed that degranulation of RER, proliferation of SER, decreasing of glycogen particles and mitochondrial swelling occurred in the cytoplasm of the hepatocytes within 2 layers around the central vein at 6 hours. After 12 hours the liver cells throughout the centrolobular area were injured. Degranulation of RER, proliferation of SER, and decreasing of glycogen particles became prominent, and mitochondria showed swelling and transformation. In the midzonal and periportal areas, numerous lipid droplets were seen in the cytoplasm of the hepatocytes. From the result of ultrastructural findings, it is considered that detoxication and biotransformation of paraquat occur in the hepatocytes within 2 layers around the central vein at an early stage, and spread to the hepatocytes throughout centrolobular area later.     

Effect of 3 amino 1,2,4 triazole administration on the early CCl4-induced ultrastructural alterations in rat liver.

CCl4 administration to rats caused at 3 and 6 h intense effects on the liver-cell endoplasmic reticulum such as dilatation, disorganization, detachment of ribosomes, development of extensive areas of smooth component (SER) and formation of myelin figures. 3 Amino 1,2,4 triazole administration (AT) at 3 and 6 h led to the formation of round small vesicles from the rough endoplasmic reticulum (RER), detachment of ribosomes, appearance of extensive areas of SER, appearance of elongated and distorted mitochondria with an increase in the number of peroxisomes. The administration of CCl4 to AT-pretreated animals led to a mutual cancellation of the effects on the RER, particularly remarkable at 3 h but still evident at 6 h; also, the formation of myelin figures was prevented. The other effects on cell ultrastructure exerted either by CCl4 or by AT were also observed with the combination of both chemicals. These observations reinforce the hypothesis about the need of either covalent binding of CCl4 metabolites to cellular constituents or lipid peroxidation, or both, in the origin of CCl4-induced alterations.     

Surface area ratios. III. A stereological method for estimating relative changes in average hepatocytes

Stereological information seems to be most interpretable, with respect to experimental changes, when related to an average cell. Current methods for obtaining an average cell volume essentially consist of dividing an aggregate volume of cells by the number of nuclei therein, assuming one nucleus per cell (Loud, ′68). Hepatocytes represent a somewhat special case, however, in that some are binucleated. Since the number of hepatocytes in one cm³ of tissue is less than the number of hepatocyte nuclei in the same cm³, dividing the hepatocytic volume by the number of nuclei gives only an average “mononuclear” hepatocyte. Such an estimate creates two interpretation difficulties: (1) the volume of an average mononuclear hepatocyte is less than that of an average hepatocyte; and (2) changes in the proportion of binucleated cells may compromise the “relative comparisons” for which the method was originally intended. The purpose of this study is to describe a new approach that can avoid these difficulties altogether, and then to assess the errors associated with the average mononuclear hepatocyte estimates. This was accomplished by combining a surface area ratio method, which can detect average cell changes without being influenced by binucleated cells, with the method of Loud (′68), which is affected as described above. The experimental model was the rat liver (n = 20) recovering for 3 days from 5 daily injections of sodium phenobarbital (100 mg/kg). The results indicate that changes in the average cell volumes for the two methods have similar slopes, but by not accounting for binucleated cells, the average mononuclear hepatocyte reference overestimates average hepatocytic volume changes by 63.1%. Similarly, the mononuclear hepatocyte reference overestimates changes in the surface areas of the ER by 32.1% (range = 26.1% to 39.1%), the SER by 21.6% (range = 14.3 to 30.1%), and the RER by 65.1% (range = 54.6% to 76.4%).     

Comparison of components of the testis interstitium with testosterone secretion in hamster,rat, and guinea pig testes perfused in vitro

Components of the testis and cytoplasmic organelles in Leydig cells were quantified with morphometric techniques in hamster, rat, and guinea pig. Testosterone secretory capacity per gram of testis and per Leydig cell in response to luteinizing hormone (LH) (100 ng/ml) stimulation was determined in these three species from testes perfused in vitro. Numerous correlations were measured among structures, and between structures and testosterone secretion, to provide structural evidence of intratesticular control of Leydig cell function. Testosterone secretion per gm testis and per Leydig cell was significantly different in the three species: highest in the guinea pig, intermediate in the rat, and lowest in the hamster. The volume of seminiferous tubules per gm testis was negatively correlated, and the volumes of interstitium. Leydig cell, and lymphatic space per gm testis were positively correlated with testosterone secretion. No correlations were observed between volumes of blood vessels, elongated spindle-shaped cells, or macrophages per gm testes and testosterone secretion. The average volume of a Leydig cell and the volume and surface area of smooth endoplasmic reticulum (SER) and peroxisomes per Leydig cell were positively correlated, and the volume of lysosomes and surface area of inner mitochondrial membrane per Leydig cell were negatively correlated with testosterone secretion. No correlations were observed between volume and surface area of rough endoplasmic reticulum (RER), Golgi apparatus, and lipid, and volume of ribosomes, cytoplasmic matrix, and the nucleus with testosterone secretion per Leydig cell. These results suggest that Leydig cell size is more important than number of Leydig cells in explaining the difference in testosterone-secreting capacity among the three species, and that this increase in average volume of Leydig cell is associated specifically with increased volume and surface are of SER and peroxisomes. An important unresolved question is what is the role of peroxisomes in Leydig cell steroidogenesis.     

Cocaine hepatotoxicity in mice: histologic and enzymatic studies

The severity of hepatotoxicity in CF-1 mice given 5 daily doses of 5, 10, and 20 mg cocaine/kg body weight and sacrificed 24 hr after the last injection appeared to be dose-dependent. Using light microscopy, the hallmark of cocaine early toxicity was manifested by pallor and ballooning of the hepatocytes in the midzonal and then in the centrilobular areas. Degeneration and necrosis of the liver cells in the same zones were encountered while the hepatocytes in the periportal areas remained intact. When examined under the electron microscope, such pallor and ballooning of the hepatocytes appeared to to be due to dilation of the rough endoplasmic reticulum (RER) profiles which often revealed a significant loss of their ribosomes. Dilation of the smooth endoplasmic reticulum (SER) was also common and moderate proliferation of peroxisomes was frequently seen. In the degenerating hepatocytes, the 2 forms of endoplasmic reticulum were difficult to recognize and the peroxisomes appeared sparse. Cocaine treatment elevated the level of glutamic pyruvic transaminase and glutamic oxaloacetic transaminase in a dose-dependent manner. Although hepatic cytochrome P450 was slightly increased in the low dose groups, a reduction in the enzyme activity was noticed in the group treated with 20 mg cocaine/kg. However, hepatic reduced glutathione content manifested a significant increase in the group which received 20 mg cocaine/kg.     

Stereology of PCB 128-induced ultrastructural alterations in the rat liver

Hepatocyte cytoplasmic alterations were stereologically determined in male and female Sprague-Dawley rats fed PCB congener 128 (2,2',3,3',4,4'-hexachlorobiphenyl) in concentrations of 0.05, 0.5, 5, 50 ppm, or corn oil in diets daily for 13 weeks. A significant increase (p < 0.05) in the volume-fraction of smooth endoplasmic reticulum (SER) was measured in the female rats fed a diet containing 5 or 50 ppm of the congener and a significant increase was revealed in the male rats at doses of 0.5 and 50 ppm. Because drug metabolizing enzymes are bound to the SER, proliferated profiles may imply heightened enzyme activity necessary to metabolize the PCB. An elevation in volume-fraction of rough endoplasmic reticulum (RER) was measured in the hepatocytes of the male rats fed 5 ppm of the congener and none of the concentrations significantly enhanced the level of RER profiles in the females. The volume-fraction values of mitochondria, peroxisomes or lipid droplets of the hepatocytes in either the males or the females were not significantly different, as were the baseline volume-fraction of parameters studied between the male and the female rats. We determined for PCB 128, when administered in a diet to Sprague-Dawley rats, the no observable adverse effect level (NOAEL) is < 0.5 ppm.     

Ultrastructure of the liver and biliary tract in health and disease

Ultrastructural studies with the transmission (TEM) and scanning (SEM) electron microscopes have added greatly to our knowledge of cellular structure and function in the liver. The normal polyhedral hepatocyte has numerous subcellular organelles, such as mitochondria, peroxisomes, lysosomes and complex rough (rer) and smooth (ser) endoplasmic reticulum. The normal hepatocyte stores glycogen, and sometimes lipid droplets, and secretes bile through the bile canaliculi between adjacent liver cells. It receives nutrients from the sinusoidal lumen across a fenestrated endothelium which is separated by the Space of Disse' from the plasma membrane. The Space of Disse' contains a scant network of reticulin fibers but no basal lamina. Two types of parasinusoidal cells are found in Disse's space: the fat storing cells of Ito, and the Pit cells which may have an endocrine function. The diseased liver has yielded much information in studies with TEM and SEM. The studies with TEM have been most helpful in studying the etiology of infectious diseases such as hepatitis B; have revealed organelle changes such as megamitochondria in cirrhosis and the fibrillar nature of alcoholic hyaline; have led to the identification of specific deposits in metabolic and storage diseases such as hemochromatosis (iron). Wilson's disease (copper), and alpha-1-antitrypsin deficiency (glycoprotein) have proven useful in identifying drug induced liver cell changes such as proliferation of SER and cholestasis, and are useful for identifying specific cell types in inflammatory and neoplastic diseases. In the future, both TEM and SEM coupled with histochemical, cytochemical, immunohistochemical and other analytic techniques will continue to add greatly to our understanding of the liver in health and disease.     

Association between mitochondria and rough endoplasmic reticulum in rat liver

Mitochondria were isolated from rat liver homogenate by both zonal and sedimentation equilibrium centrifugation. From electron microscopic examination of thin sections it was observed that 81% of the isolated mitochondria were in contact with rough endoplasmic reticulum (RER). Intact, non-sectioned mitochondria subjected to negative staining procedures appeared to show points of connection between RER and the outer mitochondrial membrane. After treatment of mitochondria with digitonin to remove outer membranes, some of the resulting mitoplasts (intact inner membranes) remained closely associated with RER. Serial section analysis of intact rat liver indicated that RER saccules fit over mitochondria like caps providing broad areas of contact between the two organelles. The RER saccules were also observed communicating with more than one mitochondrion.     

Effect of cerium on the rat liver: an ultrastructural and biochemical study.

In rats, liver steatosis and necrosis were induced by cerous chloride (CeCl3) and the evolution of these changes was examined. By electron microscopy, 17 hours after CeCl3 treatment, dilation, disorganization and degranulation of the rough endoplasmic reticulum (RER) were noted with an increase in the number and electron density of lysosome-like bodies. In addition, nuclear chromatin showed showed a marked focal electron density, and the nuclear membrane appeared to be interrupted. At 24 hours, the RER was markedly dilated and degranulated, with free ribosomes aggregated in the cytoplasm. The Golgi cisternae appeared to be empty. There was an increase in the number and size of lipid droplets, with depletion of glycogen. At 48 hours, a massive proliferation of smooth endoplasmic reticulum (SER) vesicles occurred. Large lipid droplets were scattered throughout the cytoplasm, while the mitochondria displayed mild changes. By the 8th day, the number of lipid droplets returned to normal; no abnormalities were detected in the other cell organelles. Biochemically, the total hepatic ATP levels fell significantly by the 12th hour, dropping to a minimum by the 48th hour. The liver was gradually depleted of glycogen within the first 48 hours, while hepatic triglycerides increased rapidly, reaching a peak at 96 hours. Exogenous administration of adenine, ATP (adenosine triphosphate), or tryptophan completely prevented CeCl3-induced mortality; hepatic fat accumulation and necrosis were markedly decreased. Glucose, dl-methionine, and choline had no protective effect. It appears that a defect in hepatocellular lipoprotein synthesis and/or release may be responsible for lipid accumulation.     

The effects of ethylene thiourea administration upon rat liver cells

The effect of ethylene thiourea (ETU) upon liver cells was evaluated in male Sprague-Dawley rats. ETU was administered ad libitum in drinking water at concentrations of 1, 5, 50, and 500 ppm for time intervals of 1, 2, and 5 days, 1 and 2 weeks, 1, 2, 4, and 8 months. Two additional groups of control animals received ETU-free drinking water or a diet supplemented with 0.06% 3-MeDAB. Electron microscopic evaluation of tissue samples could detect no changes in liver cell morphology of rats receiving 1, 5, or 50 ppm ETU for up to 8 months. By contrast, rats receiving 500 ppm ETU exhibited alterations in hepatic cell morphology after 4 months of exposure. These alterations included a dramatic increase in the amount of smooth endoplasmic reticulum (SER) with a concomitant reduction in rough endoplasmic reticulum (RER), and a relocation of microbodies and mitochondria to the periphery of the SER. No alterations were seen at the shorter time intervals. These changes probably represent a response to the sustained ingestion of high concentrations of highly toxic materials and most likely do not represent a specific response to ETU. No tumors were detected in any of the samples examined or in controls receiving ETU-free drinking water. Animals receiving 3-MeDAB in their diet all developed hepatic tumors within 4 months.     

Alpha-galactosyltransferase activity in the serum of frogs (Rana catesbeiana).

Human blood group 0 cells were converted into B-active cells by incubation with uridine diphosphate D-galactose and unfractionated serum from bull frog (Rana catesbeiana). Under these conditions, "Bombay" (Oh) type red cells were not converted, and group 0 foetal cells possessing a few H antigenic sites were only weakly converted into B-active cells. In addition, the agglutination titer of the converted cells with anti-H serum decreased. These results therefore indicate that the conversion depends upon the presence of H-substance on the red cells. It was concluded from the results of this investigation that the blood group B specific alpha-galactosyltransferase was present in the serum of Rana catesbeiana as well as in the human group B serum.     

The hepatic effects of hypolipidemic drugs (clofibrate, nafenopin, tibric acid, and Wy-14,643) on hepatic peroxisomes and peroxisome-associated enzymes.

Male Swiss-Webster mice were fed diets containing four hypolipidemic agents which are known to induce proliferation of hepatic peroxisomes. Treatment with all four drugs (clofibrate; its structural analogue, nafenopin; and two drugs structurally unrelated to clofibrate, tibric acid and Wy-14,643) produced a marked hepatomegaly in the mice. The extent of the increase in liver weight correlated well with the increases in total hepatic DNA and in the collective volume of hepatocyte peroxisomes. Treatment with these drugs also produced similar increases in the activities of peroxisome-associated enzymes. The most dramatic increases were noted in the activities of the short-chain (8- to 26-fold) and medium-chain (4- to 11-fold) carnitine acyltransferase. Significant increases were also noted in the activities of catalase (twofold to threefold), alpha-glycerophosphate dehydrogenase (twofold to threefold) and the long-chain carnitine acyltransferase (twofold to fourfold). Activity of the latter enzyme, however, is not known to be associated with peroxisome fractions. Concomitant administration of actinomycin D or cycloheximide with a single oral dose of clofibrate diminished the increases in liver weight and carnitine acyltransferase which occurred with clofibrate treatment alone. The finding that the major increase in activity of peroxisome enzymes occurred in those associated with metabolism of acyl CoA groups supports the hypothesis that the hypolipidemic action of the drugs and the proliferation of hepatic peroxisomes are related functions.     

Fluoxymesterone-induced inclusion bodies in dog liver

A large dose of androgenic steroid fluoxymesterone (FM) was orally administered to beagle dogs for 15 days. At sequential time intervals, liver tissues were obtained by needle biopsy for light and electron microscopic examinations. The most prominent alteration of the hepatocytes was seen at 6 to 10 days of treatment in the endoplasmic reticulum. SER had proliferated. RER had lost their parallel arrangement with loss of ribosomes and the cisternae were elongated and meandering. Multilayers of concentrically arranged paired membranes, fingerprints, had enclosed the mitochondria, microbodies, lipids, and other cytoplasmic constituents. The paired membranes were in continuity with SER and RER at the periphery of the fingerprints. Horseshoe-shaped, incomplete rings or complex forms of multilayers of the paired membranes coexisted with fingerprints. Another characteristic structure was the presence of the elongated, bent endoplasmic reticulum aligned glycogen particles between the intercisternal spaces. It seemed that these cisternal structures fuse at their ends and become glycogen-bearing fingerprints which are transformed into tightly packed smooth glycogen-free ones. The fingerprints disappeared after cessation of FM administration. These results led to the conclusion that the FM-induced fingerprints originate from elements of the endoplasmic reticulum.     

Morphometric analysis, at electron microscope level, combined with hormone assay of nonfunctioning adrenocortical adenomas: comparison with aldosterone-producing adenomas

We performed electron microscopic studies of eight nonfunctioning adrenocortical adenomas (NFA) and nine aldosterone-producing adenomas (APA) obtained from surgical specimens. A comparison of these two types of adenomas was conducted by morphometric analysis of random electron micrographs. The organelles measured included mitochondria (M), smooth-surfaced endoplasmic reticulum (SER), rough-surfaced endoplasmic reticulum (RER), lipid vacuoles (LV), and lysosomes (Ly). The content of steroid hormones, including 17-alpha hydroxyprogesterone (17-OHP), aldosterone (Ald), and other steroid hormones, was measured in adenoma tissue from six NFA and eight APA. The percentages of the areas of the organelles M, SER, and RER per total cell area in the NFA were significantly lower than those in the APA. The average content of Ald in adenoma tissues in APA was markedly higher than that in the NFA, while the mean content of 17-OHP in the NFA was significantly higher than that in APA. In conclusion, NFA are morphometrically characterized by a reduction in organelles such as M, SER, and RER, compared with findings in APA. From the quantitative analysis of steroid hormones, it was suggested that NFA produce more precursor substances with less hormone activity than APA and that steroidgenesis in NFA is shifted to a glucocorticoid pathway, as indicated by the elevated 17-OHP concentration.     

Control of intracellular Ca2+ activity in rat myometrium.

Four fractions enriched, respectively, in plasma membrane (PM), smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER), and mitochondria were isolated from estrogen-dominated rat myometrium. Ca2+ uptake by these fractions was studied in order to estimate the relative potential of the corresponding organelles for controlling intracellular Ca2+ activity. Ca2+ uptake properties of the PM, SER, and RER fractions were similar except that potentiation by oxalate was in the order RER greater than or equal SER greater than PM. However, studies with the ionophores X-537A and A23187 suggested that Ca2+ was transported into the lumen of membrane vesicles of all these fractions. Unlike that of skeletal muscle sarcoplasmic reticulum, Ca2+ uptake by the myometrial fractions was not supported by high-energy compounds other than ATP. Mitochondria took up much less Ca2+ at low, and much more Ca2+ at high, free Ca2+ concentrations than did the other fractions. The amount of Ca2+ taken up in 30 s from a 1 muM free Ca2+ solution in the presence of ATP was similar for all fractions. These results suggested that mitochondria may act as an important Ca2+ control system in rat myometrium when the intracellular Ca2+ concentration is near 1 muM or higher, whereas the PM, SER, and RER may be of major importance at Ca2+ levels of 0.3 muM or lower.