[Human serum alcaline phosphatase and ageing]. / Fosfátase alcalina sérica humana e envelhecimento.

BACKGROUND: In experimental ageing models an inverse relationship between age and alkaline phosphatase activity has been observed. OBJECTIVE: To characterize serum levels of alkaline phosphatase activity in humans according to age and gender. METHODS: Serum alkaline phosphatase was determined in a random sample of 203 community dwellers aged 40 or more years. RESULTS: In men (n=87) total serum alkaline phosphatase markedly increased from the 5th to the 6th decade and then stabilized. For women (n=116) there was a slight increase in total serum alkaline phosphatase from the 5th to the 6th decade, followed by a bend upward after 69 years of age. There was a significant positive correlation between total serum alkaline phosphatase and age for the whole population. CONCLUSIONS: Serum alkaline phosphatase activity appears as a biomarker of age in humans, similarly to what has been described for experimental animal models.

Modulation of uptake of organic cationic drugs in cultured human colon adenocarcinoma Caco-2 cells by an ecto-alkaline phosphatase activity.

Alkaline phosphatase (ALP) refers to a group of nonspecific phosphomonoesterases located primarily in cell plasma membrane. It has been described in different cell lines that ecto-ALP is directly or indirectly involved in the modulation of organic cation transport. We aimed to investigate, in Caco-2 cells, a putative modulation of 1-methyl-4-phenylpyridinium (MPP(+)) apical uptake by an ecto-ALP activity. Ecto-ALP activity and (3)H-MPP(+) uptake were evaluated in intact Caco-2 cells (human colon adenocarcinoma cell line), in the absence and presence of a series of drugs. The activity of membrane-bound ecto-ALP expressed on the apical surface of Caco-2 cells was studied at physiological pH using p-nitrophenylphosphate as substrate. The results showed that Caco-2 cells express ALP activity, characterized by an ecto-oriented active site functional at physiological pH. Genistein (250 micro M), 3-isobutyl-1-methylxanthine (1 mM), verapamil (100 micro M), and ascorbic acid (1 mM) significantly increased ecto-ALP activity and decreased (3)H-MPP(+) apical transport in this cell line. Orthovanadate (100 micro M) showed no effect on (3)H-MPP(+) transport and on ecto-ALP activity. On the other hand, okadaic acid (310 nM) and all trans-retinoic acid (1 micro M) significantly increased (3)H-MPP(+) uptake and inhibited ecto-ALP activity. There is a negative correlation between the effect of drugs upon ecto-ALP activity and (3)H-MPP(+) apical transport (r = -0.9; P = 0.0014). We suggest that apical uptake of organic cations in Caco-2 cells is affected by phosphorylation/dephosphorylation mechanisms, and that ecto-ALP activity may be involved in this process.

Regulation of [(3)H]MPP(+) transport by phosphorylation/dephosphorylation pathways in RBE4 cells: role of ecto-alkaline phosphatase.

The aim of this study was to investigate the role of phosphorylation/dephosphorylation mechanisms at the blood-brain barrier (BBB) in the uptake of organic cations. The experiments were performed using RBE4 cells, an immortalized, rat brain microvessel endothelial cell line, an in vitro model of the BBB. The modulation of the uptake of 1-methyl-4-phenylpyridinium (MPP(+)), a model organic cation, at the apical membrane of RBE4 cells was studied. Agents that stimulate protein kinase A, but not protein kinase C, produced a moderate inhibition (approximately 18% reduction) of uptake of [(3)H]MPP(+) by RBE4 cells. Okadaic acid, an inhibitor of protein serine/threonine phosphatase, did not affect uptake of (3)H-MPP(+), but the alkaline phosphatase (ALP) inhibitor levamisole markedly reduced (3)H-MPP(+) uptake. The activity of membrane-bound ALP expressed on the apical surface of RBE4 cells was studied at pH 7.4 using p-nitrophenylphosphate as substrate. Kaempferol, progesterone, 3-isobutyl-1-methylxanthine, all- trans-retinoic acid and iron stimulated ecto-ALP activity and uptake of [(3)H]MPP(+) in RBE4. Orthovanadate (a protein tyrosine phosphatase inhibitor) markedly inhibited both ecto-ALP activity and uptake of [(3)H]MPP(+) by RBE4 cells. In conclusion, these results suggest that apical transporter(s) of MPP(+) in RBE4 cells may be under the control of phosphorylation/dephosphorylation mechanisms, being active in the dephosphorylated state. A physiological role for ALP in the modulation of organic cation transport in the BBB is suggested.

Modulation of insulin transport in rat brain microvessel endothelial cells by an ecto-phosphatase activity.

The physiological function of alkaline phosphatase (ALP) remains controversial. It was recently suggested that this membrane-bound enzyme has a role in the modulation of transmembranar transport systems into hepatocytes and Caco-2 cells. ALP activity expressed on the apical surface of blood-brain barrier cells, and its relationship with (125)I-insulin internalization were investigated under physiological conditions using p-nitrophenylphosphate (p-NPP) as substrate. For this, an immortalized cell line of rat capillary cerebral endothelial cells (RBE4 cells) was used. ALP activity and (125)I-insulin internalization were evaluated in these cells. The results showed that RBE4 cells expressed ALP, characterized by an ecto-oriented active site which was functional at physiological pH. Orthovanadate (100 microM), an inhibitor of phosphatase activities, decreased both RBE4-ALP activity and (125)I-insulin internalization. In the presence of L-arginine (1 mM) or adenosine (100 microM) RBE4-ALP activity and (125)I-insulin, internalization were significantly reduced. However, D-arginine (1 mM) had no significant effect. Additionally, RBE4-ALP activity and (125)I-insulin internalization significantly increased in the presence of the bioflavonoid kaempferol (100 microM), of the phorbol ester PMA (80 nM), IBMX (1 mM), progesterone (200 microM and 100 microM), beta-estradiol (100 microM), iron (100 microM) or in the presence of all-trans retinoic acid (RA) (10 microM). The ALP inhibitor levamisole (500 microM) was able to reduce (125)I-insulin internalization to 69.1 +/- 7.1% of control. Our data showed a positive correlation between ecto-ALP activity and (125)I-insulin incorporation (r = 0.82; P < 0.0001) in cultured rat brain endothelial cells, suggesting that insulin entry into the blood-brain barrier may be modulated through ALP.

Alkaline phosphatase from rat liver and kidney is differentially modulated.

OBJECTIVE: To investigate the effect of inhibitors of alkaline phosphatase (ALP) and modulators of P-glycoprotein (Pgp), multidrug resistance protein (MRP) and hepatic taurocholate uptake on the activity of tissue-nonspecific ALP (TNALP) in liver and kidney. DESIGN AND RESULTS: ALP activity was determined in rat liver and kidney homogenates. Levamisole had a stronger inhibitory effect on renal TNALP than on the hepatic isoform. 1,3-dimethylxanthine (theophylline) almost abolished renal TNALP activity whereas its effect on hepatic TNALP was less intense. 3-isobutyl-1-methylxanthine (IBMX) and lidocaine produced opposite effects, activating hepatic TNALP and inhibiting the kidney isoform. Quinidine significantly inhibited renal TNALP without affecting hepatic TNALP. Kaempferol activated both liver and kidney isoforms, the effect being more pronounced on hepatic TNALP. CONCLUSIONS: a) renal TNALP seems to be more sensitive to inhibition than hepatic TNALP, b) TNALP activity studies should take into account the source of ALP isoform and c) ALP pharmacological manipulation in vivo may produce different and even opposite effects in different tissues/organs.

Effect of fasting on rat duodenal and jejunal microvilli.

Duodenal and jejunal ultrastructural morphology and total serum alkaline phosphatase (ALP) activity were investigated in Wistar rats submitted to normal feeding, a 24 h fasting without or with access to sawdust or expanded polystyrene, and a 22 h fasting followed by a 2 h refeeding. Ultrastructural observation of duodenal and jejunal villous tips showed the occurrence of degenerating epithelial cells that were much more frequent in the epithelium of fasted rats. Refeeding and ingestion of sawdust or expanded polystyrene decreased the mean percentage of degenerating cells in the duodenum but not in the jejunum in comparison to plain fasted animals. Normal feeding produced the highest value of serum ALP activity. Refeeding as well as ingestion of sawdust or expanded polystyrene increased serum ALP activity values from those of plain fasted state: the difference being significant only for the refed group. It is concluded that: a) feeding, for both duodenum and jejunum, and refeeding and mechanical stimulation, just for the duodenum, increased proliferation, decreased apoptosis or facilitated desquamation of the epithelium; b) ALP increase in serum was induced by feeding and refeeding.

[The discovery of the body]. / A descoberta do corpo.

This paper initially recognises that the human body tends to implicate itself in the current triad in which it gains evidence (body, soul and spirit). Its discovery is, therefore, a difficult cognitive process. In the conveyance of the message that one has from the body to the desideratum of its knowledge, the possibility of discovery fulfills itself in the adventure of its study where religious, artistic and scientific paths distinctively appear as modes of evidence. As discovery is usually entrusted on medicine it is nowadays important that the latter should pronounce itself on acquired knowledge. Health and its re-establishment after illness are correlated with the knowledge of the body! In order for the allegations regarding the body's rights over the body to be more than mere phantasmagoric exorcisms, it is necessary to consider the knowledge of the body as an experience, particularly, of existing, of having and of being.

Differences between duodenal and jejunal rat alkaline phosphatase.

OBJECTIVES: The aim of this study was to kinetically characterize rat tissue-nonspecific-alkaline phosphatase (TNS-ALP) and intestinal (duodenal- and jejunal-IALP), and to determine the effect of substances known to affect phosphorylation/dephosphorylation on TNS- and IALP activity. DESIGN AND RESULTS: The ranking order of ALP activity (K(enzyme)) was duodenal mucosa (IALP) > jejunal mucosa (IALP) > kidney (TNS-ALP) > brain (TNS-ALP). Levamisole was found to produce a concentration-dependent decrease of ALP activity in kidney and brain. However, levamisole had no effect on duodenal ALP activity and produced a concentration-dependent increase on jejunum ALP activity. In brain and jejunum homogenates, octreotide, a stable somatostatin analogue, produced a concentration-dependent increase in ALP activity. In relation to duodenum ALP activity, octreotide produced a biphasic effect.Reverse transcription-polymerase chain reaction showed the presence of IALP-I mRNA both in duodenal and jejunal mucosa, but IALP-II only in duodenal mucosa. CONCLUSIONS: The results show that duodenal- and jejunal-IALP differ in kinetic parameters and in drug sensitivity. Thus, we can speculate on a different physiologic role for duodenal- and jejunal-IALP, particularly in relation to their dephosphorylation targets.

Effect of P-glycoprotein modulators on alkaline phosphatase activity in cultured rat hepatocytes.

Alkaline phosphatases (orthophosphoric-monoester phosphohydrolase, E. C. 3.1.3.1) are a group of nonspecific phosphomonoesterases located primarily in the plasma membrane of the cells in which they occur [1]. It was recently demonstrated that alkaline phosphatase (ALP) concentration in different tissues is positively correlated with the extent of exchange surface per unit volume of the tissue, suggesting an association between ALP and transport systems [2]. Moreover, several groups [3,4,5] obtained evidence of an involvement of ALP in the modulation of P-glycoprotein activity in hepatocytes. The aim of the present study was to determine the putative influence of compounds known to modulate P-glycoprotein-mediated transport on hepatic ALP activity, by using primary cultured rat hepatocytes. The K(m) and V(max) values of ALP were determined (657.2 microM (306.8-933.1) and 32.0+/-1.5 nmol mg protein(-1) min(-1), respectively). Vanadate and corticosterone concentration-dependently reduced ALP activity, producing maximal reductions of 79% (100 microM) and 71% (100 microM), respectively. The IC50's were found to be 7.9 microM (2.1-29.5 microM) and 2.4 microM (0.2-35.2 microM), respectively. Cyclosporin A, verapamil, octreotide, kaempferol, daunomycin and genistein produced a concentration-dependent increase in ALP activity. ALP activity was maximally increased to 253%, 390%, 180%, 487%, 449% and 193% of control in the presence of 100 microM cyclosporin A, 50 microM verapamil, 10 microM octreotide, 100 microM kaempferol, 100 microM daunomycin and 1 microM genistein, respectively. The results show that all P-glycoprotein modulators tested were able to significantly affect the activity of hepatic-ALP. These effects on ALP activity may contribute to the modulation of P-glycoprotein activity by these drugs.

Physiologic concentrations of bile salts inhibit rat hepatic alkaline phosphatase but not the intestinal isoenzyme.

OBJECTIVE: The effect of bile salts on alkaline phosphatase (EC 3.1.3.1) activity from Wistar rat liver, duodenum, jejunum, and serum was investigated. DESIGN AND RESULTS: For concentrations higher than 1 mM conjugated bile salts (glycocholate, glycochenodeoxycholate, taurocholate, taurodeoxycholate, and taurochenodeoxycholate) inhibited hepatic ALP but, up to concentrations of 10 mM, had no effect on intestinal ALP. Also cholate, deoxycholate, and chenodeoxycholate, within the same concentration range, did not have any effect on intestinal ALP. ALP inhibition induced by conjugated bile salts was significantly higher in serum of starved rats than in serum of fed animals, what is in good agreement with the known higher proportion of hepatic ALP and lower proportion of intestinal ALP in serum of starved rats. CONCLUSIONS: Bile salts can, thus, be used to help discriminating between tissue-nonspecific and intestinal ALP isoenzymes and identifying pathologic conditions where the relative quantities of these isoenzymes are altered in serum. Inhibition of hepatic ALP by physiologic concentrations of bile salts may bear some relation to the bile salts effects on their own enterohepatic circulation and/or biosynthesis.

Importance of assay conditions in visualization and quantitation of serum alkaline phosphatase isoenzymes separated by electrophoresis.

The importance of separation and identification of serum alkaline phosphatase (ALP; E.C. 3.1.3.1) fractions/isoenzymes has been frequently reported. Each serum ALP fraction/isoenzyme quantitation has both practical and theoretical importance. In the present work, serum was collected from Wistar rats and, in identical experimental conditions, total serum ALP activity and serum ALP electrophoretic fractions/isoenzymes activities were quantified. Different results for both kinds of ALP activity were obtained when different buffers or mixture of these buffers (carbonate/bicarbonate; 2-amino-2-methyl-1-propanol/HCl; Veronal, sodium diethylbarbiturate/HCl), pH conditions (9.4 and 10.4) and substrates (alpha- and beta-naphthyl phosphates) were used. Higher total serum ALP activity was always observed with beta-naphthyl phosphate, independently of the buffer (or mixture of buffers) and pH used. Electrophoresis allowed the separation of two serum ALP fractions. Activity of both serum ALP electrophoretic fractions was always higher with beta-naphthyl phosphate, except with carbonate/bicarbonate pH 10.4. The effect of a change in pH was buffer- (or mixture of buffers) and substrate-dependent; the addition of a second buffer (to that previously used) was not always accompanied by an increase or decrease (of the same magnitude) in our results. The results obtained with different buffers (or mixture of buffers) were not identical with substrates and pH values. It is concluded that (i) from the same electrophoretic separation of serum ALP fractions/isoenzymes, different values for its activity can be obtained by changing the assay conditions used for ALP visualization (revelation, staining); (ii) the same assay conditions for quantitation of total serum ALP and serum ALP electrophoretic fractions/isoenzymes should be used; (iii) the choice of assay conditions should take into account the biochemical problem being studied in each case.

Effect of bile duct obstruction on hepatic uptake of 1-methyl-4-phenylpyridinium in the rat.

Previous studies have demonstrated that the organic cation 1-methyl-4-phenylpyridinium (MPP+) is avidly taken up by rat freshly isolated hepatocytes through at least two distinct transport mechanisms: the type I hepatic transporter of organic cations and P-glycoprotein. In this study, the effects of extrahepatic cholestasis induced by bile duct ligation for 4 days on the uptake of [3H]MPP+ by rat freshly isolated hepatocytes and liver slices were determined. Bile duct ligation produced no significant alterations in the characteristics of [3H]MPP+ uptake by freshly isolated hepatocytes. The strong correlation found between the effect of various drugs on [3H]MPP+ uptake by hepatocytes from control and treated rats (r = 0.958; P < 0.0001; n = 15) suggests that neither the type I hepatic transporter of organic cations nor P-glycoprotein were affected by bile duct ligation. On the contrary, uptake of [3H]MPP+ by liver slices was markedly changed after bile duct ligation: (1) there was a significant increase (approximately equal to 40%) in the amount of [3H]MPP+ taken up by liver slices from bile duct-ligated rats; (2) there was no correlation between the effect of various drugs on [3H]MPP+ uptake by liver slices from control and treated rats (r = 0.772; P= 0.072; n = 6). On the basis of (1) the lack of effect of bile duct ligation on [3H]MPP+ uptake by isolated hepatocytes; and (2) the profound morphological alterations of liver tissue observed 4 days after bile duct ligation (increase in volume density of bile ductules, ductular cells and infiltration of inflammatory cells), we suggest that non-parenchymal liver cells have an important participation in the hepatic uptake of [3H]MPP+ after bile duct ligation in the rat.

Postnatal development of organic cation transport in the rat liver.

Previous studies have demonstrated that the small permanently charged organic cation 1-methyl-4-phenylpyridinium (MPP+) is avidly taken up by rat hepatocytes. The aim of this study was to characterise the postnatal development of hepatic uptake of organic cations, using the model compound MPP+. Accumulation of [3H]MPP+ by liver slices obtained from rats ranging from 1 day to 7 weeks was measured, and the effect of a series of compounds on [3H]MPP+ uptake was examined. The accumulation of [3H]MPP+ by liver slices was similar in adult (87.5 +/- 19.9 pmol g-1; n = 7) and neonatal rats (110.6 +/- 11.5 pmol g-1; n = 15). Verapamil, quinidine (100 microM) and progesterone (200 microM) produced very marked reductions on [3H]MPP+ uptake at all ages, and the inhibitory effect of verapamil and quinidine was maximum in livers from 1-day-old rats. Bilirubin (200 microM) significantly reduced [3H]MPP+ uptake by liver slices from 1 day, 1 week and 7-week-old rats. However, [3H]MPP+ accumulation was reduced by cimetidine, vinblastine and daunomycin (100 microM) in 1-day-old rats, but the effect of these drugs disappeared as the animals age increased. These findings demonstrate that hepatic organic cation uptake capacity is remarkably high shortly after birth and suggest that at least two distinct uptake mechanisms are involved in this process. These uptake systems are the type I hepatic transporter of organic cations, active from birth to adulthood, and P-glycoprotein, active only in very young rats.

Rat serum alkaline phosphatase electrophoretic fractions: variations with feeding, starvation and cellulose fibre ingestion.

The effect of feeding, starvation and fibre ingestion on alkaline phosphatase (ALP) activity (E.C. 3.1.3.1) was studied in Wistar rat serum. Using identical assay conditions for total ALP activity determination and for electrophoretic ALP isoenzymes/fractions activity calculation, alpha- and beta-naphthyl phosphates and p-nitrophenyl phosphate were used as substrates and 2-amino-2-methyl-1-propanol/HCI was used as buffer, respectively. Total activity with beta-naphthyl phosphate was significantly higher than with alpha-naphthyl phosphate and p-nitrophenyl phosphate; with alpha-naphthyl phosphate it was significantly higher than with p-nitrophenyl phosphate. With all substrates, fed animals had significantly higher total activity than starving ones. Electrophoresis allowed the separation of two fractions. The second fraction activity was significantly higher in the fed group than in the starving ones, irrespective of the substrate used. Starving animals with fibre showed higher values of this fraction than starving animals without fibre, the difference reaching statistical significance with alpha-naphthyl phosphate. The first fraction predominated in both starved groups and the second in the fed group. The second fraction was identified as intestinal ALP. We conclude that the mechanical stimulation of the digestive tract appears to influence the passage of intestinal ALP to serum. The experimental conditions used enable quantification of electrophoretic fractions based on total activity. Activity depends on the substrate used.

Inward transport of [3H]-1-methyl-4-phenylpyridinium in rat isolated hepatocytes: putative involvement of a P-glycoprotein transporter.

1. The liver has an important role in the detoxification of organic cations from the circulation. [3H]-1-methyl-4-phenylpyridinium ([3H]-MPP+), a low molecular weight organic cation, is efficiently taken up and accumulated by rat hepatocytes through mechanisms partially unknown. 2. The aim of the present work was to characterize further the uptake of MPP+ by rat isolated hepatocytes. The putative interactions of a wide range of drugs, including inhibitors/substrates of P-glycoprotein, were studied. 3. The uptake of MPP+ was investigated in rat freshly isolated hepatocytes (incubated in Krebs-Henseleit medium with 200 nM [3H]-MPP+ for 5 min) and in the rat liver in situ (perfused with Krebs-Henseleit/BSA medium with 200 nM [3H]-MPP+ for 30 min). [3H]-MPP+ accumulation in the cells and in tissue was determined by liquid scintillation counting. 4. Verapamil (100 microM), quinidine (100 microM), amiloride (1 mM), (+)-tubocurarine (100 microM), vecuronium (45 microM), bilirubin (200 microM), progesterone (200 microM), daunomycin (100 microM), vinblastine (100 microM), cyclosporin A (100 microM) and cimetidine (100 microM) had a significant inhibitory effect on the accumulation of [3H]-MPP+ in isolated hepatocytes. Tetraethylammonium (100 microM) had no effect. 5. In the rat perfused liver, both cyclosporin A (100 microM) and verapamil (100 microM) had much less marked inhibitory effects as compared to their effects on isolated hepatocytes (0% against 35% and 45% against 96% of inhibition, respectively). 6. Inhibition of alkaline phosphatase activity by increasing or decreasing the pH of the incubation medium or by the presence of vanadate (1 mM) or homoarginine (500 microM) led to a significant increase in the accumulation of [3H]-MPP+ in isolated hepatocytes. 7. It was concluded that, in addition to the type I organic cation hepatic transporter, [3H]-MPP+ is taken up by rat hepatocytes through P-glycoprotein, a canalicular transport system that usually excretes endobiotics and xenobiotics. We proposed that the reversal of transport through P-glycoprotein may be related to the loss of efficacy of alkaline in isolated hepatocytes.

A correlated morphological and biochemical study on the rat adrenal steroidogenesis.

The ultrastructural and biochemical alterations produced by an hypocholesterolemic drug, 17 alpha-ethinyl estradiol, on the rat adrenal cortex were studied. Male rats aged two months and with approximately 200 g in weight were injected subcutaneously with 10 mg/kg/day of ethinyl estradiol during 9 days; rats injected with 1 ml propylene glycol were used as controls. The animals were sacrificed on the 10th day, and the adrenals from some of them were processed for electron microscopy. The adrenals from the remaining rats were used for measurements of the glands cholesterol and corticosterone, which were also measured in the blood. In estradiol-treated rats the zona fasciculata cells exhibited numerous microvilli, increase in the size of mitochondria and decrease in the number of lipid droplets. The quantitative analysis showed a significant increase of the volumetric density of mitochondria and microvilli and a significant decrease of the lipid droplets in the treated rats, when compared with normal ones. In treated rats, the concentration of cholesterol and corticosterone in the gland and blood were significantly decreased. These data show that hypocholesterolemia produced by estradiol has a remarkable effect on adrenal steroidogenesis, depletes the pool of adrenal cholesteryl esters, and evidences the role of plasma cholesterol in the corticosteroidogenesis.

Ultrastructural and biochemical alterations produced in rat adrenal cortex by 4-aminopyrazolopyrimidine.

The ultrastructural and biochemical changes produced by 4-aminopyrazolo[3,4-d]pyrimidine (4-APP), on zona fasciculata cells of rat adrenal cortex are described. Male rats weighing approximately 200 g were injected intraperitoneally with 50 mg/kg/day of 4-APP for 3 days; the controls were injected with buffer. All animals were sacrificed on the 4th day and the adrenals from some of them were processed for electron microscopy. The adrenals from the remaining rats were used for measurements of gland cholesterol and corticosterone; the latter was also measured in the blood. In 4-APP-treated rats the zona fasciculata cells exhibited an increase in the amount of smooth endoplasmic reticulum and in the number of free ribosomes, often arranged in polyribosomes, and a decrease in the number of lipid droplets. The nucleus showed scarce condensed chromatin and nucleolar fragmentation. The quantitative analysis showed a significant increase of the volumetric density of endoplasmic reticulum and a significant decrease of the lipid droplets in treated rats when compared with controls. Concerning the nucleus, the volumetric density of condensed chromatin significantly decreased, while the relative volume of fibrillar centers, and of granular and vacuolar components increased. In treated rats, the adrenal cholesterol and corticosterone concentrations and the blood corticosterone level were significantly decreased. These data show that 4-APP has a remarkable effect on corticosteroidogenesis and depletes the pool of adrenal cholesteryl esters, and these data stress the importance of plasma cholesterol in the steroidogenesis; on the other hand the drug appears to have a direct effect on the nucleus.

Effects of the inhalation of enflurane on hepatic microsomal enzymatic activities in the rat.

We have investigated the possible hepatic microsomal enzyme induction effect of enflurane, administered by inhalation in anaesthetic doses for periods of 1 h a day. In 15 experimental groups, differing from one another in anaesthetics concentration (1, 2 and 3% enflurane) and in the number of days of treatment (3, 7, 10, 14, 21 and 24) we found (1) no alteration either in the ratio of liver to body weight or in the microsomal protein content; (2) no modifications in aniline hydroxylase activity; (3) a decrease in the aminopyrine demethylase activity after a number of exposures, varying with the dose.