Prevention of lethal acute graft-versus-host disease in mice by oral administration of T helper 1 inhibitor, TAK-603.

Acute graft-versus-host diseases (GVHD) is a major cause of morbidity and mortality in patients undergoing allogeneic bone marrow transplantation (BMT). T helper 1 (Th1)-type cytokines such as interferon-gamma or tumor necrosis factor-alpha have been implicated in the pathogenesis of acute GVHD. TAK-603 is a new quinoline derivative, which is now in clinical trials for use as a disease-modifying antirheumatic drug. In preclinical studies, it inhibited delayed-type hypersensitivity, but not Arthus-type reaction, in mice, and selectively suppressed Th1 cytokine production. Thus, the present study was designed to investigate whether the Th1 inhibitor (TAK-603) ameliorates lethal acute GVHD in a mouse model. Administration of TAK-603 into BALB/c mice given 10 Gy total body irradiation followed by transplantation of bone marrow and spleen cells from C57BL/6 mice markedly reduced the mortality in association with minimal signs of GVHD pathology in the liver, intestine, and skin. TAK-603 reduced not only the production of Th1-type cytokines, but also the proportion of Th1 cells in CD4(+) helper T cells in this GVHD mouse model. These results suggest that TAK-603 could be a potent therapeutic agent for acute lethal GVHD.

Effects of lisinopril and nitrendipine on urinary albumin excretion and renal function in patients with mild to moderate essential hypertension.

The present study was designed to evaluate the effects of an ACE inhibitor, lisinopril, and a calcium antagonist, nitrendipine, on urinary albumin excretion (UAE) and renal function in mild to moderate essential hypertensive patients with microalbuminuria. After the 4-week drug-free period, 17 patients were randomly divided into two groups. The first group (group 1: n=8) received lisinopril 10-20 mg daily for 8 weeks followed by nitrendipine 5-10 mg daily for another 8 weeks. The second group (group 2: n=9) received nitrendipine 5-10 mg daily for 8 weeks followed by lisinopril 10-20 mg daily for another 8 weeks. The mean blood pressure (MBP) significantly decreased in a similar manner in both groups. UAE significantly decreased after 8 weeks of treatment with lisinopril in group 1 and after 8 weeks of subsequent treatment with lisinopril in group 2. On the other hand, UAE was not altered by treatment with nitrendipine. The changes in UAE were significantly correlated with changes in MBP after 8 weeks of treatment with nitrendipine, but not after 8 weeks of treatment with lisinopril. No significant changes in creatinine clearance, urinary excretion of sodium or urinary N-acetyl-beta-D-glucosaminide were observed by any treatment in either group. These results suggest that lisinopril, not nitrendipine, reduces UAE in essential hypertensive patients with microalbuminuria independently of its effective antihypertensive properties.

Enhancement of the growth of Helicobacter pylori in Brucella broth by hydrogen peroxide.

We found that a sub-lethal concentration of hydrogen peroxide (HPOx) enhanced the growth of Helicobacter pylori in Brucella broth supplemented with 10% fetal bovine serum (BB/FBS). The enhancement was evident at 0.1 mM HPOx and reached a maximun at 3.5 mM. The growth stimulation was dependent on the basal media used; when brain heart infusion broth (BHIB) was used instead of BB, the growth was not altered regardless of the presence or absence of HPOx. Furthermore, the growth in BHIB/FBS was comparable to that in BB/FBS plus 3.5 mM HPOx. This suggested that the enhancement of growth by HPOx resulted from the derepression of the inhibitory factor existing in BB by HPOx. The inhibitory substance seemed to be bisulfite salt since the bacteria grew to a similar extent in bisulfite-less Brucella broth (BLBB0)/FBS compared to the bacterial growth in BHIB/FBS and BB/FBS plus HPOx. These results indicate that the detoxification of bisulfite in BB can be easily achieved by simply adding HPOx to the medium, which causes the oxidation of bisulfite to bisulfate, a less-toxic compound to the bacterial growth. Since we also found that the morphology and cellular protein profile of BB/FBS-cultured bacteria were apparently different from those cultured in BLBB/FBS, we propose that the use of BB for primary isolation and cultivation of H. pylori should be limited on certain occasions, or if necessary, BB can be used after detoxification of the bisulfite by the addition of a low concentration of HPOx.

Inorganic polyphosphate kinase is required to stimulate protein degradation and for adaptation to amino acid starvation in Escherichia coli.

Inorganic polyphosphate (polyP) kinase was studied for its roles in physiological responses to nutritional deprivation in Escherichia coli. A mutant lacking polyP kinase exhibited an extended lag phase of growth, when shifted from a rich to a minimal medium (nutritional downshift). Supplementation of amino acids to the minimal medium abolished the extended growth lag of the mutant. Levels of the stringent response factor, guanosine 5'-diphosphate 3'-diphosphate, increased in response to the nutritional downshift, but, unlike in the wild type, the levels were sustained in the mutant. These results suggested that the mutant was impaired in the induction of amino acid biosynthetic enzymes. The expression of an amino acid biosynthetic gene, hisG, was examined by using a transcriptional lacZ fusion. Although the mutant did not express the fusion in response to the nutritional downshift, Northern blot analysis revealed a significant increase of hisG-lacZ mRNA. Amino acids generated by intracellular protein degradation are very important for the synthesis of enzymes at the onset of starvation. In the wild type, the rate of protein degradation increased in response to the nutritional downshift whereas it did not in the mutant. Supplementation of amino acids at low concentrations to the minimal medium enabled the mutant to express the hisG-lacZ fusion. Thus, the impaired regulation of protein degradation results in the adaptation defect, suggesting that polyP kinase is required to stimulate protein degradation.

[Two cases of functioning parathyroid cysts].

Two cases of functioning cysts are reported. The first patient was a 48-year-old man who underwent percutaneous cyst puncture for a palpable mass in the neck at another hospital. Hypercalcemic crisis brought the patient to Koga General Hospital. The second patient was a 69-year-old woman with the complaint of discomfort in the right neck of several years duration and with a palpable mass identified on physical examination at a local hospital. Both patients had high serum calcium and parathyroid hormone (PTH) levels and were diagnosed as having functioning parathyroid cysts by imaging studies including ultrasonography, computed tomographic scan, magnetic resonance imaging and scintigraphy. After parathyroidectomy, their serum calcium and PTH levels became normal, but calcium supplement was necessary in the first patient. To our knowledge, these are the 40th and 41st cases reported in the Japanese literature.

[Surgery and multidisciplinary treatment for colorectal cancer].

Evaluation of surgery and multidisciplinary treatment for colorectal cancer was performed based on the review of the results of clinical trials. Although most improvement in prognosis for colorectal cancer patients was obtained by the development of surgical techniques until the mid-70's, further extended surgery could not have demonstrated the obvious improvement in survival after the 80's. In this regard, various multidisciplinary treatments were evaluated by a meta-analysis of clinical trials. Among those modalities, preoperative irradiation for rectal cancer, postoperative adjuvant chemotherapy for resected colorectal cancer and biochemical modulation of 5-fluorouracil by methotrexate or leucovorin for advanced colorectal cancers proved to be significantly effective for improvement of prognosis. Clinical trials of immunochemotherapy using either levamisole or PSK for resected colorectal cancers, a trial of hepatic artery infusion for liver metastasis, and a trial of an adjuvant monoclonal antibody treatment, were also reported to demonstrate significant effects. For further progress in multidisciplinary treatment for colorectal cancers, standardization of the appropriate surgical technique for each stage of the disease is much anticipated.

[Neoadjuvant chemotherapy in high-grade advanced gastric cancer with protracted infusional 5-fluorouracil and consecutive low-dose cisplatin].

Twenty-one evaluable patients with primary gastric cancer/local invasion, liver metastasis and peritoneal metastasis were entered in a pilot study of neoadjuvant chemotherapy that used continuous 24-hour infusion 5-FU, 330 mg/m2/day plus low dose CDDP, 6 mg/m2 daily by bolus infusion d1-5. This regimen was repeated for 4 weeks. The overall response rate was 52%, including one complete and ten partial responses. The response rate of differentiated adenocarcinomas was significantly higher than that of poorly differentiated adenocarcinomas. In 15 patients (71%), gastrectomy and lymphadenectomy could be done after this regimen. chemotherapy-induced downstaging from the initial clinical stage was pathologically found in 5 patients who underwent gastrectomy. Toxicity was primarily hematologic. Leukopenia and thrombocytopenia of grade 3 or 4 occurred in 19% and 14% of patients, respectively. The patients were able to take meals during therapy and preserved good quality of life. Median survival time was 11 months for the cancers with liver metastasis and five of the 8 locally advanced cancers are alive 11 months after the therapy. This therapy was effective for patients with high-grade advanced gastric cancer.

Estradiol-induced diurnal changes in lactotroph proliferation and their hypothalamic regulation in ovariectomized rats.

Pentobarbital anesthesia during the proestrous afternoon delays proliferation of lactotrophs of the anterior pituitary from estrus to diestrus 1 in cycling female rats. We determined whether estradiol treatment induced diurnal changes in rates of lactotroph proliferation in ovariectomized rats, and if so, examined whether hypothalamic neural activity was involved in the occurrence of the estradiol-induced diurnal changes. Dispersed anterior pituitary cells were obtained from ovariectomized rats bearing estradiol implants that had been treated with 5-bromo-2'-deoxyuridine (BrdU) 3 h before decapitation. BrdU-labeling indices representative of the proliferation rate of lactotrophs were determined by double immunofluorescence staining for BrdU and PRL. After treatment of ovariectomized rats with estradiol on day 0, BrdU-labeling indices of lactotrophs as determined by injecting BrdU at 1000 h increased markedly with time peaking on days 4-7. Levels of BrdU-labeling indices at 1000 h on day 4 were 2.8-fold higher than those at 2200 h on day 3 or 4 after estradiol treatment. However, levels of BrdU-labeling indices at 1000 h on day 14 were 35% lower than those at the same time on day 4 and did not differ from those at 2200 h on day 13 or 14. In addition, a difference in BrdU-labeling indices as observed between 1000 and 2200 h on day 4 in the ovariectomized rats was not detected in estradiol-treated orchidectomized male rats. Serial determinations of BrdU-labeling indices throughout day revealed that the difference in BrdU-labeling indices between 1000 and 2200 h on day 4 in the ovariectomized rats reflected estradiol-induced diurnal changes that were characterized by a peak between 0700-0900 h and a nadir between 1900-2200 h. Pentobarbital injected at 0900 or 2100 h on day 3 decreased slightly high levels of BrdU-labeling indices at 0800 h on day 4. However, pentobarbital injection at 1345 h on day 3, which was effective in blocking estradiolinduced surges of LH and PRL secretion, suppressed markedly the high levels at 0800 h on day 4. In these pentobarbital-blocked rats, the diurnal changes in BrdU-labeling indices whose peak would normally have occurred at 0700-0900 h on day 4 were delayed not by the time corresponding to the duration of pentobarbital anesthesia but exactly by 24 h. These results suggest that 1) hypothalamic and sexually dependent diurnal changes in lactotroph proliferation can be induced by short-term estradiol treatment in ovariectomized rats as well as in cycling rats, and 2) estradiol treatment for 14 days rather prevents the diurnal changes in lactotroph proliferation.

Existence and expression of the untranslated first exon of aromatase mRNA in the rat brain.

Tissue-specific expression of aromatase activity and mRNA occurs by alternative utilization of multiple untranslated first exons and promoters in the human. The major transcript in the human brain contains the brain-specific first exon, "exon I-f". However, few reports on the untranslated first exon of aromatase mRNA in the rat brain have been available so far. In the present study, we investigated the existence and expression of exon I-f in the rat brain to elucidate the mechanism of the tissue-specific expression of the brain aromatase. Total RNA extracted from amygdala (AMY) was subjected to a reverse transcription-polymerase chain reaction (RT-PCR). The nucleotide sequence of the RT-PCR product had 89.4% homology to the corresponding region of exon I-f of the human aromatase cDNA. It was indicated that the major transcript in the rat AMY contained exon I-f by the use of a rapid amplification of cDNA ends (RACE). Furthermore, in order to determine the distribution of the aromatase mRNA with exon I-f, total RNAs from the hypothalamus-preoptic area (HPOA), AMY, testis and ovary were analysed by RT-PCR using the primers specific for the mouse exon I-f and the primers for the rat exon III-V. Significant levels of PCR products were found in all tissues with the highest level being in the ovary, using the primers for exon III-V. On the other hand, using the primers for exon I-f, the levels of signals from HPOA and AMY were higher than those from the testis and ovary. These results suggest that tissue-specific expression of aromatase mRNA occurs by an alternative utilization of multiple promoters in the rat, as in the human. It should be noted that minor transcripts containing exon I-f were observed in the testis and ovary.

[Anesthetic management of a patient with ornithine transcarbamylase deficiency].

A 6-year-old female with disturbance of consciousness (JCS: 3 points) due to hyperammonemia caused by ornithine transcarbamylase deficiency is presented. She underwent an emergency insertion of a catheter for peritoneal dialysis under general anesthesia. Anesthesia was induced by intravenous administration of thiamylal sodium and maintained with inhalation of sevoflurane and oxygen after tracheal intubation. One percent mepivacaine was infiltrated around the surgical field to diminish the dose of sevoflurane. The operation proceeded uneventfully, although her consciousness could not recover rapidly to the normal level during the emergence from anesthesia. Peritoneal dialysis was started immediately after the operation and her consciousness recovered to the normal level gradually during the following six days with decreasing plasma ammonia levels. Ten days later, extirpation of the peritoneal catheter was scheduled. The course of anesthesia and operation was uneventful using the same anesthetic method as with the former anesthesia. In the anesthetic management for a patient with ornithine transcarbamylase deficiency, we have to be careful about the nitrogen balance, which can be affected by the kind and doses of anesthetic drugs, to avoid hyperammonemia. From this point of view, local anesthesia combined with general anesthesia might be useful to prevent the serum ammonia level from increasing.

Pentobarbital anesthesia during the proestrous afternoon blocks lactotroph proliferation occurring on estrus in female rats.

Estradiol stimulates the synthesis and secretion of PRL and lactotroph proliferation, and its long-term administration induces PRL-secreting pituitary tumors. We examined changes in the number of proliferating lactotrophs throughout the estrous cycle in female rats and the involvement of the brain in the regulation of the lactotroph proliferation by anesthetizing with pentobarbital. Female rats revealing regular 4-day estrous cycles were injected ip with the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) 3 h before decapitation to label DNA-replicating cells. Dispersed anterior pituitary cells obtained from these rats were stained for PRL and BrdU with a double labeling immunofluorescence technique. The rate of lactotroph proliferation was represented by the BrdU-labeling index (BrdU-labeled lactotrophs as a percentage of total lactotrophs counted). Lactotrophs from rats injected with BrdU at 1000 h showed a high BrdU-labeling index of 2.6% on estrus, whereas they showed almost undetectable levels of the BrdU-labeling index during the other stages of the estrous cycle. The anterior pituitary cells other than lactotrophs were scarcely labeled during any stages. The BrdU-labeling index began to rise by the midnight between proestrus and estrus, peaked between 0800 and 1200 h, and returned to undetectable levels by the midnight between estrus and diestrus I. Pentobarbital (35 mg/kg, i.p.) injected at 1345 h on proestrus, which was effective in blocking ovulation on estrus, eliminated completely the increase in the BrdU-labeling index as determined by BrdU injection at 1000 h on estrus. In contrast, the high BrdU-labeling index on estrus was partly suppressed to a level of 1.4% by pentobarbital injection at 0900 or 2100 h on proestrus. The rats injected with pentobarbital at 1345 h on proestrus did not show any increases in the BrdU-labeling index even after BrdU injection was delayed from 1000 to 1400 h on estrus. However, a high BrdU-labeling index of 3.7% was obtained in these animals when BrdU was injected at 1000 h on diestrus I. We conclude that 1) lactotrophs of cycling female rats proliferate selectively on the day of estrus; and 2) the proliferation of lactotrophs on estrus is not due to a direct action on the anterior pituitary of estradiol secreted from the ovaries but triggered by neural events occurring during the proestrous afternoon, which are closely related with the regulation of preovulatory surges of gonadotropin and PRL secretion.

The ontogeny of gene expression of progestin receptors in the female rat brain.

The postnatal development of the progestin receptor (PR) system in the rat brain is a region-specific and stage-related process. In an attempt to analyze the molecular mechanism by which the dramatic change of gene expression of the PR occurs we have examined the level of PR mRNAs in the hypothalamus-preoptic area (HPOA) and cerebral cortex in development from fetal to postnatal stages of female rats. We used polymerase chain reaction to clone, from uterine cDNA, the cDNA corresponding to the steroid-binding domain of the PR forms 'A' and 'B' mRNA as well as the region around the translation-initiation site (ATG1) of the putative PR form 'B' mRNA. A quantitative reverse transcription-polymerase chain reaction assay was used to measure the level of mRNAs for PR forms 'A' and 'B' (total PR mRNAs) and PR form 'B'. There was a regional difference in the intracerebral distribution between the total and form 'B' mRNAs, indicating possible distinct mechanisms responsible for regulating the expression of the PR mRNAs. The PR mRNAs in the brain, already detectable 2 days before birth, increased at early neonatal stages. The total PR mRNAs in the cortex developed in a manner essentially similar to the PR protein at the early stages, but, surprisingly, unlike the receptor, the messages remained high at the later stages from day 18 to 8 weeks of life. On the other hand, the ontogeny of the cortical mRNA for form 'B', which predominantly existed in the region, resembled that of the cortical PR protein. In the HPOA the postnatal development of the form 'B' mRNAs was also roughly similar to the PR. These results suggest region-specific and stage-related gene expression of the PR isoform system in the developing brain: gene expression of form 'B' seems to be predominantly, first, "turned on" around birth, followed by form 'A' mRNA expression around days 8-12. Moreover, lowered levels of the cortical PR mRNAs in the propylthiouracil-induced hypothyroid rat, together with suppressed PR level, indicate a possible regulatory role of thyroid hormone on gene expression of the cortical receptor.

Presence of sex difference of cytochrome P-450 in the rat preoptic area and hypothalamus with reference to coexistence with oxytocin.

Localization of female type cytochrome P-450 (F1) in the preoptic area and hypothalamus of the rat was examined immunocytochemically using antiserum against purified hepatic P-450 (F1). This antiserum recognizes both P-450 (F1) and P-450 (M3). Western immunoblotting using the antiserum demonstrated that female rat brain contains P-450 (F1) but not P-450 (M3), since microsomes from the brain and liver displayed only one immunoreactive band at 50 kD, coinciding with that of P-450 (F1) purified from female rat liver. On the other hand, the male brain has P-450 (M3) but not P-450 (F1), as liver- and brain-derived microsomes produced single band at 49 kD, which represents a mol. wt. identical to that of P-450 (M3) extracted from male rat liver. These results indicate that P-450 (F1)-like immunoreactivity (LI) occurs in the female rat brain, while P-450 (M3)-LI takes place in the male rat brain. Immunocytochemical analysis further demonstrated the detailed cellular localization of these two P-450-LIs in the preoptic area and hypothalamus of female and male rats. Localization of P-450 (F1)-LI in the female rat hypothalamus resembled that of P-450 (M3)-LI in the male rat hypothalamus. Magnocellular neurosecretory neurons in the paraventricular nucleus and supraoptic nucleus were labeled and were found to contain oxytocin but lack vasopressin when serial sections of these areas were analyzed. In addition, groups of immunoreactive cells were seen in the median preoptic nucleus, medial and lateral preoptic area, caudal portion of the bed nucleus of the stria terminalis, lateral hypothalamus at the level of the paraventricular nucleus, periventricular zone from the preoptic area to the paraventricular nucleus, and parvocellular portion of the paraventricular nucleus.

Simultaneous determination of pantothenic acid and hopantenic acid in biological samples and natural products by gas chromatography-mass fragmentography.

A method for the simultaneous determination of pantothenic acid and hopantenic acid in plasma samples was developed using gas chromatography-mass spectrometry with multiple ion detection. Plasma samples were directly purified without deproteinization on an ion-exchange resin, and the eluate was extracted with ethyl acetate under acidic conditions. The organic layer was evaporated to dryness under a stream of nitrogen, and the residue was dissolved in an internal standard solution. Pantothenic and hopantenic acids were converted into their trimethylsilyl derivatives by treating with bis(trimethylsilyl)trifluoroacetamide. Aliquots of this solution were injected into the gas chromatograph-mass spectrometer, which was equipped with a wide-bore fused-silica column (DB-17) and analysed by the multiple ion detection method. The detection limits for pantothenic acid and hopantenic acid in plasma were 1 ng/ml each at a signal-to-noise ratio of 5. This method was applied to a study of the assay of pantothenic acid and hopantenic acid in biological samples and natural products.

Arachidonic acid as a possible modulator of estrogen, progestin, androgen, and glucocorticoid receptors in the central and peripheral tissues.

In an attempt to learn whether modulation of steroid hormone receptor by arachidonate is generalized or not, the arachidonate effect was examined in cytosol estrogen (ER), progestin (PR), androgen (AR) and glucocorticoid receptors (GCR) from the central and peripheral tissues of rats by sucrose density gradient centrifugation, and gel filtration on LH20 columns or dextran-coated charcoal absorption. Arachidonate and other long-chain fatty acids appear to inhibit the specific binding of estrogen ([3H]R2858), progestin ([3H]R5020), androgen ([3H]R1881) and glucocorticoid ([3H]dexamethasone) to the respective receptors in brain (neonatal cerebral cortex and hypothalamus-preoptic area, HPOA), uterus and prostate, with the exception of the potentiating effect on the brain estrogen receptors. The potency of the unsaturated fatty acids paralleled to some degree the number of cis double bonds and carbon, in that oleate (C18:1) arachidonate (C20:4) docosahexaenoate (C22:6). The arachidonate inhibition was dose-dependent in the tissue steroid hormone receptors, except for dose-dependent potentiation of the brain cortical estrogen receptors. Inhibitory potency as expressed by the concentration for 50% maximum inhibition (Ki) was in the range of 11-18 microM for the receptors other than the uterine estrogen receptors with the value of 44 microM, suggesting lower sensitivity for the estrogen receptor to the arachidonate effect in the uterus. Analysis on kinetics and Scatchard plot revealed the non-competitive type of the inhibition. In addition, arachidonate lowered dose-dependently the peak of labelled progestin or estrogen binding to the 8S receptor proteins, which were collected from fractions in the 8S region of the cytosols from intact or diethylstibestrol-primed rat uteri. These results suggest the generalized modulatory effect of arachidonate on the steroid hormone receptors in the central and peripheral tissues. Arachidonate could affect, negatively or positively, the estrogen receptors, and negatively the progestin, androgen and glucocorticoid receptors, through a possibly direct but weak binding at sites different from steroid binding sites on the receptor molecules. A potential messenger role of arachidonate itself has been implicated in the regulation or modulation of the steroid hormone receptors.

Serum transferrin receptor as a new index of erythropoiesis.

Serum transferrin receptors were measured by a sandwich radioimmunoassay procedure in patients with iron deficiency anemia, autoimmune hemolytic anemia and aplastic anemia. The mean circulating transferrin receptor concentration of normal subjects and patients with iron deficiency anemia, autoimmune hemolytic anemia and aplastic anemia are 253 +/- 82 ng/mL, 730 +/- 391 ng/mL, 1,426 +/- 1,079 ng/mL, and 182 +/- 39 ng/mL, respectively. The values for those with iron deficiency anemia and autoimmune hemolytic anemia were significantly higher than that of normal controls and the values for those with aplastic anemia were lower than that of normal controls. After iron supplementation in iron deficiency anemia, the serum transferrin receptor values increased twofold over those of pretreatment values. This increase parallels an increase in peripheral reticulocytes. Therefore, the number of circulating transferrin receptors in anemic patients may reflect the level of bone marrow erythropoiesis and is a potentially useful new index for red cell production.

Decreased progestin receptors in the cerebral cortex of hypothyroid postnatal rats.

The effects of neonatal hypothyroidism were examined on the concentrations of cytosol receptors for progestin and estrogen in the cytosols from 10-day old female and male rats. The concentration of cytosol progestin- and estrogen receptors in the 10-day old female and male rats with propylthiouracil-induced hypothyroidism was determined by multiconcentration saturation analysis. Neonatal hypothyroidism markedly depressed the level of progestin receptors in the cortex but not in the hypothalamus-preoptic area (HPOA). There were no differences in the concentration of estrogen receptors in the cortex and HPOA between the control and PTU rats. These results suggest that thyroid hormone may be one of the factors affecting the development of progestin receptors in the cortex. Its significance was discussed in relation to determination of the length of sexual differentiation of the rat brain.

The ontogeny of cytosol and nuclear progestin receptors in male rat brain and its male-female differences.

The fetal and postnatal development of the progestin receptor systems in the intact male rat brain was investigated by means of the in vitro cytosol binding and the nuclear exchange assay using [3H]R5020 [( 17 alpha-methyl-3H]17 alpha, 21-dimethyl-19-nor-4, 9-pregnadiene-3,20-dione). The cortical cytosol receptors, first detectable at day 0, rapidly increased at day 7, reaching a maximum at day 10, then gradually declined thereafter. The receptors in the HPOA appeared clearly at day 1, increased during the first 10 days, then remained constant at days 14-21. The postnatal developmental patterns of cytosol brain progestin receptors in males were essentially similar to those in females, but there were some differences between both sexes. The male HPOA at days 10-14 contained more receptors than the female one. Nuclear progestin binding was low in the neonatal male brain at days 1-3. Despite the low level of serum progesterone, the cortical nuclear binding suddenly increased at days 7-10, then remained high at days 14-21. A similar, though less pronounced, pattern was seen in the HPOA. The male pattern of nuclear binding, thus, essentially resembled the female one. However, lower binding in the cortex and, possibly, HPOA was found in males than in females at days 10-21. After progesterone injection postnatal male rats accumulated a lower concentration of progestin receptors in the cortex and, possibly, HPOA than similarly-treated females. It is concluded from these results that progestin receptors in male rat brain appear immediately after birth and develop differentially in the cortex and HPOA. The sudden onset of increased nuclear translocation of endogenous progestin receptor complexes may occur in the brain at around days 7-10. There is a marked sex difference in the nuclear progestin receptor system in the postnatal brain, particularly the cortex. Moreover, the postnatal male brain has lower capacities of nuclear receptor translocation than does the female one. The progestin receptor system in the cortex and, possibly, HPOA of rats in the early postnatal life might be involved with some processes in the mechanism of sexual differentiation of the brain.