Administration Of Hemin Research Articles

Heme oxygenase-1 is upregulated in the kidney of angiotensin II-induced hypertensive rats : possible role in renoprotection.

In this study, we investigated the regulation and physiological role of heme oxygenase-1 (HO-1) in the kidney of rats with hypertension. Rats were continuously administered either angiotensin II (Ang II) or norepinephrine with an osmotic minipump for up to 7 days. Ang II infusion decreased the glomerular filtration rate (GFR) as determined through creatinine clearance (3.2+/-0.2 versus 1.2+/-0.2 mL/min with Ang II infusion, P<0.01) and increased proteinuria (9. 7+/-1.3 versus 28.1+/-7.2 mg/d with Ang II infusion, P<0.01). In contrast, norepinephrine did not alter these laboratory values. Ang II infusion significantly increased HO-1 expression in mRNA (442+/-98% of control at day 5, P<0.01) and protein levels (314+/-49% of control at day 5, P<0.01). Immunohistochemistry showed that in the kidney of normotensive rats, HO-1 was expressed mainly in the basal side in the renal tubules. After Ang II infusion, HO-1 staining was more extensively dispersed in the tubular epithelial cells. The intraperitoneal administration of zinc protoporphyrin, an HO inhibitor, to Ang II-infused rats further decreased GFR (0.8+/-0. 1 mL/min) and increased proteinuria (52.5+/-13.0 mg/d). In contrast, the administration of hemin, an HO inducer, ameliorated the Ang II-induced decrease in GFR (2.4+/-0.2 mL/min) and increase in proteinuria (9.3+/-4.5 mg/d). These data suggest that HO-1 upregulation in the kidney of Ang II-induced hypertensive rats may exert a renoprotective effect against Ang II-induced renal injury.

Balloon Injury Does Not Induce Heme Oxygenase-1 Expression, but Administration of Hemin Inhibits Neointimal Formation in Balloon-Injured Rat Carotid Artery

It has been shown that antioxidant agents act inhibitorily against neointimal formation after balloon injury, suggesting the role of oxidative stress as a promotor of intimal cell proliferation. Heme oxygenase-1 (HO-1) is an inducible form of heme catabolizing enzyme that is induced by and acts against oxidative tissue injury. In this set of experiments, we showed that HO-1 was present in newly formed neointima; however, arterial HO-1 expression did not increase in response to balloon injury in rat carotid artery. Intraperitoneal administration of hemin, a HO-1 inducer, for 5 consecutive days resulted in about a 4-fold increase of serum bilirubin concentration. In addition, hemin injection increased HO-1 protein expression in the carotid artery, the heart, the kidney, and the liver. In this condition, balloon injury-induced neointimal formation was markedly inhibited. Local application of tin protoporphyrin, a HO inhibitor, blocked this effect, suggesting that induced HO-1 in the carotid artery was responsible for the inhibition of neointimal formation after balloon injury. This study suggests that induction of the endogenous antioxidant gene can suppress neointimal formation after balloon injury.

Heme availability affects corticosterone and aldosterone biosynthesis in rat adrenal

In this paper, we studied the effect of heme availability on corticosterone and aldosterone synthesis in rat adrenal. We found that hemin stimulated corticosterone and aldosterone production in adrenal homogenates in a dose-dependent fashion. Hemin administration to rats also provoked an increase in both corticosterone and aldosterone content in adrenal. 3,5-Diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine (DDC), an inhibitor of liver ferrochelatase activity, was able to inhibit this enzyme in rat adrenal. This resulted in an impairment of heme concentration and consequently adrenal ALA-synthase and porphyrin content were increased. Thus, it was proven that DDC inhibits heme biosynthesis in adrenal as it does in liver. In vivo experiments with rats showed that DDC was able to partially blocked ACTH-mediated corticosterone and aldosterone production while hemin administration was able to partially restore it. These data indicate that heme availability affects steroid biosynthesis in rat adrenal.

A 65-kDa Protein Mediates the Positive Role of Heme in Regulating the Transcription of CYP2B1/B2 Gene in Rat Liver

Heme deficiency precipitated by CoCl2 administration to rats leads to a striking decrease in the inducibility of CYP2B1/B2 mRNA levels and its transcription by phenobarbitone (PB), besides decreasing the basal levels. Exogenous hemin administration counteracts the effects of CoCl2 administration. The binding of nuclear proteins to labeled positive cis-acting element (-69 to -98 nucleotides) in the near 5'-upstream region of the gene is inhibited by CoCl2 administration to saline or PB-treated rats, as assessed in gel shift assays. Administration of exogenous hemin to the animal or addition in vitro to the extracts is able to overcome the effects of CoCl2 treatment. The protein mediating this effect has been purified from CoCl2 administered nuclear extracts by heparin-agarose, positive element oligonucleotide affinity, and heme affinity column chromatography. This 65-kDa protein manifests very little binding to the positive element, but in the presence of certain other nuclear proteins, shows a strong heme-responsive binding. The purified protein binds heme. It is also able to stimulate transcription of a minigene construct of the CYP2B1/B2 gene containing -179 nucleotides of the 5'-upstream region and the I exon in a cell-free system, manifesting heme response. It is concluded that the 65-kDa protein mediates the constitutive requirement of heme for the transcription of CYP2B1/B2 gene.

Regulation of Ferritin H-Chain Expression in Differentiating Friend Leukemia Cells

The mechanisms that regulate the expression of ferritin, the iron storage protein, have been investigated in Friend erythroleukemia cells (FLCs) induced to differentiate by several chemical compounds. In differentiating FLCs, administration of hemin increases the steady-state level of ferritin mRNA about 15-fold and the ferritin content about 20- to 25-fold. Conversely, iron salts have only mild stimulatory effects on these parameters and iron chelators only slightly inhibited the stimulatory effect of hemin. Transient transfection experiments with a construct in which the human ferritin H-chain promoter drives the expression of the indicator chloramphenicol acetyltransferase (CAT) gene show that the increase in mRNA content is mainly due to enhanced transcription. In addition to transcriptional effects, translational regulation resulting in the further increase in ferritin synthesis is shown by CAT assays from cells transiently transfected with a construct containing the coding region for the indicator CAT mRNA under the translational control of the mRNA ferritin iron-responsive element. We conclude that, in FLCs induced to differentiate, hemin acts synergistically with the differentiation inducers, increasing ferritin expression. Both transcriptional and translational mechanisms are responsible for this synergistic effect, which appears to be characteristic of differentiated erythroid cells because it is not observed in other cell types (ie, fibroblastic cell lines).

Characterization of 2,3,7,8-tetrachlorodibenzo- p-dioxin-induced brain serotonin metabolism in the rat

It has previously been shown that a lethal dose of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) increases the brain concentrations of serotonin precursor, tryptophan, and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in TCDD-suceptible Long-Evans but not in TCDD-resistant Han/Wistar rats. In the present study, TCDD (50 μg/kg; LD 100 for Long-Evans and nonlethal for Han/Wistar rats) enhanced de novo biosynthesis of serotonin in the brain of Long-Evans but not Han/Wistar or food-restricted Long-Evans rats 10 days after exposure. Furthermore, TCDD increased the plasma level of free trytophan in Long-Evans rats alone, which may be causally related to the observed effects of TCDD on brain tryptophan levels. Administration of hemin modified the time course of TCDD-induced anorexia although 10 day cumulative food consumption was not altered. Hemin tended to attenuate TCDD-elicited increases in brain serotonin turnover, whereas a β-adrenergic blocker, propranolol, did not. In the majority of Long-Evans rats, TCDD inhibited the main tryptophan degrading enzyme in the liver, tryptophan pyrrolase, but the rest exhibited augmented activities; these effects were not altered by hemin. TCDD increased the plasma levels of nonesterified fatty acids in Long-Evans (five-fold) but not in Han/Wistar rats. A slight elevation (two-fold) was also seen in food-restricted Long-Evans rats. It is concluded that TCDD selectively promotes brain serotonin turnover in Long-Evans rats and this acceleration is related to increased plasma levels of free tryptophan. The inhibition of tryptophan catabolism in the liver and elevation of plasma nonesterified fatty acids may contribute to these changes.

Anti-tumor effect of IL-2 and hemin on murine renal cell carcinoma

Hemin, which is the mitogenic oxidizing agent, has immunostinulatory properties for murine splenocytes. We studied the anti-tumor effect of hemin with IL-2 by using murine renal cell carcinoma (Renca). Treatment of cells with hemin and IL-2 resulted in a marked enhancement of mitogenicity and generation of cytotoxicity in vitro. These enhancements were achieved at low dose of IL-2. Splenocytes isolated from mice that had been treated with hemin and IL-2 incorporated increased amounts of 3H-thymidine during 20 hours incubation in vitro. Treatment with the combination of hemin and IL-2 was more effective than either hemin or IL-2 alone. The combination of hemin and IL-2 was effective in inducing cytotoxicity for Renca. Induction of cytotoxicity was optimal at the hemin concentration of 10 microM, and higher concentrations were less effective. In vivo administration of hemin and IL-2 in Renca bearing mice resulted in a significant survival prolongation. IL-2 alone, at the dose used, was ineffective. The anti-tumor effect was enhanced by administration of N-acetylcysteine and by nephrectomy. Since hemin can safely be administered to patients, it may represent a new class of biologic response modifiers that could enhance IL-2 mediated anti-tumor effects.

Modulation of ferritin H-chain expression in Friend erythroleukemia cells: transcriptional and translational regulation by hemin.

The mechanisms that regulate the expression of the H chain of the iron storage protein ferritin in Friend erythroleukemia cells (FLCs) after exposure to hemin (ferric protoporphyrin IX), protoporphyrin IX, and ferric ammonium citrate (FAC) have been investigated. Administration of hemin increases the steady-state level of ferritin mRNA about 10-fold and that of ferritin protein expression 20-fold. Experiments with the transcriptional inhibitor actinomycin D and transfection studies demonstrate that the increment in cytoplasmic mRNA content results from enhanced transcription of the ferritin H-chain gene and cannot be attributed to stabilization of preexisting mRNAs. In addition to transcriptional effects, translational regulation induces the recruitment of stored mRNAs into functional polyribosomes after hemin and FAC administration, resulting in a further increase in ferritin synthesis. Administration of protoporphyrin IX to FLCs produces divergent transcriptional and translational effects. It increases transcription but appears to suppress ferritin mRNA translation. FAC treatment increases the mRNA content slightly (about twofold), and the ferritin levels rise about fivefold over the control values. We conclude that in FLCs, hemin induces ferritin H-chain biosynthesis by multiple mechanisms: a transcriptional mechanism exerted also by protoporphyrin IX and a translational one, not displayed by protoporphyrin IX but shared with FAC.

Modulation of ferritin H-chain expression in Friend erythroleukemia cells: transcriptional and translational regulation by hemin.

The mechanisms that regulate the expression of the H chain of the iron storage protein ferritin in Friend erythroleukemia cells (FLCs) after exposure to hemin (ferric protoporphyrin IX), protoporphyrin IX, and ferric ammonium citrate (FAC) have been investigated. Administration of hemin increases the steady-state level of ferritin mRNA about 10-fold and that of ferritin protein expression 20-fold. Experiments with the transcriptional inhibitor actinomycin D and transfection studies demonstrate that the increment in cytoplasmic mRNA content results from enhanced transcription of the ferritin H-chain gene and cannot be attributed to stabilization of preexisting mRNAs. In addition to transcriptional effects, translational regulation induces the recruitment of stored mRNAs into functional polyribosomes after hemin and FAC administration, resulting in a further increase in ferritin synthesis. Administration of protoporphyrin IX to FLCs produces divergent transcriptional and translational effects. It increases transcription but appears to suppress ferritin mRNA translation. FAC treatment increases the mRNA content slightly (about twofold), and the ferritin levels rise about fivefold over the control values. We conclude that in FLCs, hemin induces ferritin H-chain biosynthesis by multiple mechanisms: a transcriptional mechanism exerted also by protoporphyrin IX and a translational one, not displayed by protoporphyrin IX but shared with FAC.

Structure, turnover, and heme-mediated suppression of the level of mRNA encoding rat liver delta-aminolevulinate synthase.

lambda gt11 cDNA libraries were constructed with poly(A)+ RNA preparations from both porphyric chicken and rat livers. A cDNA which encodes chicken hepatic delta-aminolevulinate synthase was cloned by screening with an anti-chicken liver delta-aminolevulinate synthase antibody. Using this cDNA as a probe, cDNAs encoding the entire protein coding sequence of rat hepatic delta-aminolevulinate synthase were then cloned. The complete nucleotide sequences of the cDNAs have been determined. The result predicts that the rat hepatic pre-delta-aminolevulinate synthase comprises 642 amino acids. We measured the half-life of the hepatic delta-aminolevulinate synthase mRNA by RNA blot hybridization analysis using allylisopropylacetamide-induced porphyric rats as an experimental model and the rat cDNA as a hybridization probe. The half-life of the mRNA determined by the injection of alpha-amanitin is as short as 20 min. This value is significantly shorter than the estimated half-lives of most other mRNAs in the differentiated tissues of animals. The effect of hemin administration on the level of hepatic delta-amino-levulinate synthase mRNA was also examined. The half-disappearance time of the mRNA after the hemin administration was essentially the same as that determined by alpha-amanitin or actinomycin D, and no additive effect was observed between alpha-amanitin and hemin on the half-life determination. The results provide convincing evidence that heme inhibits the transcription of delta-aminolevulinate synthase mRNA.

Regulation of 5-aminolevulinate synthase mRNA in different rat tissues.

cDNA clones for rat liver 5-aminolevulinate synthase have been isolated and used to examine mRNA levels in different rat tissues. Northern hybridization analysis of total RNA from various rat tissues showed the presence of a single 5-aminolevulinate synthase mRNA species of estimated length 2.3 kilobases. Primer extension and RNase mapping studies indicated that the mRNA is identical in all tissues. Highest basal levels were seen in liver and heart. Administration of hemin to rats reduced the basal level of this mRNA only in liver but the heme precursor, 5-aminolevulinate (or its methyl ester), repressed the basal levels in liver, kidney, heart, testis, and brain. The drug 2-allyl-2-isopropylacetamide increased the mRNA level in liver and kidney only while human chorionic gonadotropin hormone elevated the level in testis. Administration of the heme precursor 5-aminolevulinate prevented these inductions. Nuclear transcriptional run-off experiments in liver cell nuclei showed that 2-allyl-2-isopropylacetamide and 5-aminolevulinate exert their effect by altering the rate of transcription of the 5-aminolevulinate synthase gene. The results indicate that a single 5-aminolevulinate synthase mRNA is expressed in all tissues and that its transcription is negatively regulated by heme.

Regulation of intestinal mucosa guanylate cyclase by hemin, heme and protoporphyrin IX

Mg 2+-dependent activity of intestinal brush border guanylate cyclase was stimulated 4–5-fold by 50–100 μM hemin. Higher concentrations were inhibitory. In the presence of 25% dimethyl sulfoxide, which stimulated activity 9-times, 50 μM hemin further increased activity 1.7-fold. However, when activity was stimulated 32-fold by the Escherichia coli heat-stable enterotoxin, or 26-fold by Lubrol PX, hemin produced only concentration-dependent inhibition. The first type of activation was more sensitive to hemin than the second. Reduction of hemin by dithiothreitol eliminated stimulation of basal activity, while inhibition of Lubrol PX-stimulated activity remained. Protoporphyrin IX also had no effect on basal activity, however, it inhibited enterotoxin- and Lubrol PX-stimulated activities similarly, but only to half the extent of hemin. Substitution of Mn 2+ for Mg 2+ elevated basal activity 15-fold, and this Mn 2+-dependent activity was inhibited by hemin. Mn 2+-dependent activity was stimulated (43%) by enterotoxin, however, the stimulated activity was more sensitive to hemin inhibition than the basal Mn 2+-dependent activity and both inhibition curves were congruent above 50 μM hemin. Hemin inhibition of Lubrol PX-stimulated activity was much less with Mn 2+ than with Mg 2+. These results were interpreted as suggesting two sites of hemin inhibition; on an inhibitory regulator and on the enzyme. We also found that the secretory effect of enterotoxin in the suckling mouse bioassay was reduced 56% by the oral administration of hemin.

Evidence of hemin as an end product inhibitor of L-alanine:4,5-dioxovalerate transaminase in rat liver mitochondria

This study describes the in vitro and in vivo effect of hemin on L-alanine:4,5-dioxovalerate transaminase activity. Hemin was shown to be an inhibitor of the purified enzyme and this inhibition was proportional to the concentration of hemin. The examined kinetic data with hemin showed uncompetitive inhibition for both alanine and 4,5-dioxovalerate. An apparent k i of 30 and 42 μ M for hemin were obtained with both alanine and 4,5-dioxovalerate, respectively. Moreover, the enzyme activity in liver was considerably decreased after the intravenous hemin administration and such an inhibition is dose and time dependent. Furthermore, maximum inhibition of the enzyme was observed 30 min after hemin injection and 60% enzyme inhibition was achieved with a dose of 1.2 mg kg body wt of rat. Thus is suggests the important role of this enzyme on heme biosynthesis. L-Alanine: 4,5-dioxovalerate transaminase Heme biosynthesis Hemin End product inhibitor

The influence of propranolol on the concentration of heme and on the activity of δ-aminolevulinate synthase in monolayers of chick embryo liver cells

The addition of propranolol to monolayers of chick embryo liver cells caused a rapid increase in cellular heme, followed by an equally rapid decrease. Subsequently the concentration of heme rose at a relatively slower rate. About 10 hr after addition of propranolol to the medium a plateau level was reached at ± 35% above control values. Changes in the activity of δ-aminolevulinate synthase (ALAS) were negatively correlated with those of cellular heme. Cycloheximide prevented the above phenomenon. ALAS activity was not clearly correlated with the rapid, partial inhibition of protein synthesis, caused by propranolol. These observations are related to the beneficial influence of administration of hemin or of propranolol to patients with acute attacks of hepatic porphyria.

Effects of hemin on the synthesis and intracellular translocation of delta-aminolevulinate synthase in the liver of rats treated with 3,5-dicarbethoxy-1,4-dihydrocollidine.

The administration of hemin to rats which had been treated with 3,5-dicarbethoxy-1,4-dihydrocollidine (DDC) brought about a rapid decrease of the delta-aminolevulinate (ALA) synthase activity in the mitochondria and an appreciable increase of the enzyme activity in the cytosol in the liver. In DDC-treated rats, however, the degree of accumulation of ALA synthase in the liver cytosol resulting from the hemin administration was relatively small and the total ALA synthase activity in the liver was considerably decreased after the hemin administration; these results are in contrast with those for allylisopropylacetamide-treated rats. Further studies by combined use of [3H]leucine and an anti-ALA synthase IgG revealed that incorporation of [3H]leucine into the mitochondrial ALA synthase was greatly reduced in hemin-injected rats and that incorporation of [3H]leucine into total ALA synthase in the liver (the sum of radioactivity incorporated into the mitochondrial enzyme and the cytosolic enzyme) was also decreased to a considerable extent in these rats; this decrease in incorporation of [3H]leucine appeared to occur immediately after the administration of hemin. It was concluded that hemin actually inhibits the translocation of ALA synthase from the cytosol into the mitochondria and that hemin also inhibits de novo synthesis of ALA synthase, possibly at a post-transcriptional level in DDC-treated rats.

Immunochemical Studies of the Turnover of δ-Aminolevulinate Synthase in Rat Liver Mitochondria and the Effect of Hemin on It1

The half-life of delta-aminolevulinate (ALA) synthase in the liver mitochondria of allylisopropylacetamide-treated rats was estimated to be about 35 min, taking advantage of the observation that hemin strongly inhibits the translocation of ALA synthase from the liver cytosol into the mitochondria. ALA synthase accumulating in the liver cytosol in allylisopropylacetamide-treated rats is rapidly translocated into mitochondria with a half-disappearance time of about 20 min, but does not appear to undergo degradation until it is translocated into mitochondria. A study with an ALA synthase-specific IgG revealed that the decrease in the ALA synthase activity in the liver mitochondria observed after the administration of cycloheximide or hemin effectively paralleled the decrease in the amount of immunologically reactive protein, providing further evidence that ALA synthase is rapidly degraded in the mitochondria.

Cardiac δ-aminolevulinic acid synthetase activity: Effects of fasting, cobaltous chloride and hemin

Cardiac δ-aminolevulinic acid (ALA) synthetase activity was studied in animals that had been fasted. The kinetics of the decline in cardiac ALA synthetase activity were measured for 48 hr after food was withdrawn from rats. A marked rate of decrease in activity was observed between 12 and 24 hr. Cardiac ornithine decarboxylase activity also decreased in fasted rats, but cardiac tyrosine aminotransferase activity remained unchanged. Cardiac ALA synthetase activity also decreased in fasted mice but did not decrease significantly in fasted guinea pigs or fasted rabbits whose activites were low even in the fed state. Cobaltous chloride administration caused a marked decrease in cardiac ALA synthetase activity which remained low for a longer duration of time than has been observed in rat liver. The administration of hemin, which causes a marked decrease in hepatic ALA synthetase activity. had no effect on cardiac ALA synthetase activity. The difference in the responses of hepatic and cardiac ALA synthetase activities to hemin administration and food deprivation suggests differential regulation of ALA synthetase activity in heart and liver.

Effect of Treatment with Hemin on Rat Liver Catalase1

Rats were injected with a single or repeated doses of hemin intraperitoneally, and the effect on liver catalase [EC 1.11.1.6] was studied. A single administration of hemin caused a reduction in the concentration of liver catalase, both in enzymatic activity and in catalase protein determined immunochemically. The reduction occurred a few hours after the hemin injection, and is probably due to stimulated degradation. Disappearance of radioactivity from liver catalase prelabelled with [14C]leucine was enhanced following the administration of hemin. No evidence for a repression in vivo incorporation of [14C]leucine and [3H]sigma-aminolevulinic acid into liver catalase was obtained with hemin-treated rats. When the hemin was given repeatedly at 12-h intervals, the level of liver catalase decreased considerably. However, the impairment in catalase-synthesizing activity of liver cells of rats thus treated was rather slight, when examined in a cell-free system. Some differences were noted between the results in the present study and those in previous investigations with Sedormid-treated rats.

Points from letters: Any future for graduate medical students?

Objective: To report a case of variegate porphyria (VP) who presented with severe hepatic dysfunction followed by acute sensorimotor axonal neuropathy. Background: Porphyrias are group of metabolic diseases caused by enzymes deficiency in heme biosynthetic pathway. VP is a rare type caused by protoporphyrinogen oxidase deficiency. The common manifestations are acute neurovisceral attacks and skin photosensitivity, but presentation with severe hepatic dysfunction is rare. Methods: Case analysis and literature review. Results: We report a 26-year-old woman who initially presented with abdominal pain, severe hyperbilirubinemia, elevated liver enzymes, and generalized edema for one month. Extensive workup for liver failure including blood test, imaging, liver biopsy, genetic testing failed to identify a cause. The patient was placed on transplant list. Later, she developed progressively generalized muscle weakness of hands and legs with tingling sensation within one week. Physical exam revealed moderate distal muscle weakness with impaired sensation, but no skin lesion. Nerve conduction study confirmed sensorimotor axonal polyneuropathy with predominant sensory involvement. Tests for common etiologic diagnosis of neuropathy were negative. Acute porphyria was one of differential diagnosis. Typical pattern of porphyric neuropathy is predominant motor neuropathy. Sensory predominant is uncommon presentation. The blood and urine tests suggested VP: negative urine delta-aminolevulinic acid, normal urine porphobilinogen (at two weeks), elevated total and subtotal plasma porphyrins, elevated urine coproporphyrin, and normal uroporphyrin. She received intravenous glucose for four days without improvement. After hemin administration and removal of hormonal intrauterine device, her liver function and motor power gradually improved, but paresthesia persisted for the following several months. Conclusions: Severe hepatic dysfunction without skin lesion is a rare manifestation of VP which makes the diagnosis challenging. Acute neuropathy, even with uncommon pattern, is a presentation that helps in diagnosis of this uncommon disease. Early administration of hemin and removal of precipitating triggers are essential treatment. <b>Disclosure:</b> Dr. Ruthirago has nothing to disclose. Dr. Julayanont has nothing to disclose. Dr. Tantikittichaikul has nothing to disclose. Dr. Kim has nothing to disclose.

Mechanism of allylisopropylacetamide-induced increase of δ-aminolevulinate synthetase in liver mitochondria: Effects of administration of glucose, cyclic AMP, and some hormones related to glucose metabolism

The allylisopropylacetamide-induced increase of δ-aminolevulinate synthetase in the rat liver was significantly reduced when any one of glucose, ATP, cyclic 3′,5′-AMP, dibutyryl cyclic 3′,5′-AMP, theophylline, insulin, or glucagon was given to rats simultaneously with the administration of allylisopropylacetamide. Administration of these substances to the rats not given allylisopropylacetamide resulted in decrease in enzyme activity in the liver. However, when these substances were given to rats after an intensive induction had commenced, the level og δ-aminolevulinate synthetase in the liver cytosol increased greatly, while the enzyme level in the mitochondria decreased markedly, so that the increase in the total activity of δ-aminolevulinate synthetase in the liver was not appreciably reduced except that the total activity in the glucose-treated rats was considerably lower than that in the control rats. Moreover, the half-life of the δ-aminolevulinate synthetase in cytosol was much longer when rats were given dibutyryl cyclic AMP. These findings are quite similar to those observed after the administration of hemin to rats treated or untreated with allylisopropylacetamide and suggest that these substances, as well as hemin, inhibit in some way both the induction of δ-aminolevulinate synthetase and the conversion of the cytosol δ-aminolevulinate synthetase to the mitochondrial δ-aminolevulinate synthetase. Dibutyryl cyclic AMP and glucagon were effective even in alloxan-diabetic rats, suggesting that the effects of cyclic AMP and glucagon may not be mediated by insulin.