Modified Dingchuan Decoction treats cough-variant asthma by suppressing lung inflammation and regulating the lung microbiota

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Dingchuan Decoction (MDD) is a Chinese medicine formula containing 11 materials with cough suppression, asthma relief, and anti-inflammatory effects.

AIM OF THE STUDY

This study aimed to evaluate the therapeutic effect of MDD on cough-variant asthma (CVA) and to investigate its mechanism of action.

MATERIALS AND METHODS

The chemical constituents of MDD were analyzed by ultra-performance liquid chromatography-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). A guinea pig CVA model was established using an intramuscular injection of ovalbumin (OVA), combined with an intraperitoneal injection of aluminum hydroxide [Al(OH)₃] and nebulized OVA. At the beginning of day 18, the low, medium, and high MDD groups were gavaged with 7.23 g/kg, 14.46 g/kg, and 28.92 g/kg of MDD, respectively, and the positive group was gavaged with 5 mg/kg of prednisone acetate combined with 1 mg/kg of montelukast sodium; the normal and model groups were given an equal volume of distilled water, once a day for 21 days. The cough was induced by 10^-3 mol/L capsaicin solution 1 h after the last administration, and the number of coughs and the latency of coughs were evaluated. Hematoxylin and eosin staining (H&E) was used to observe pathological changes in the lungs and airways. The concentration of inflammatory factors in bronchoalveolar lavage fluid (BALF) was measured by enzyme-linked immunosorbent assay (ELISA). We analyzed the lung microbiota using 16 S ribosomal DNA (16 S rDNA) high-throughput sequencing.

RESULTS

The 38 chemical components were found in MDD, and MDD reduced the number of coughs in guinea pigs with CVA, prolonged cough latency, improved pathological damage to the lungs and airways, regulated inflammatory factor levels in BALF, and modulated the lung microbiota.

CONCLUSIONS

This study demonstrated that treating CVA with MDD may be related to inhibiting lung inflammation and regulating lung microbiota.

Systematic Analysis of the Mechanism of Polygoni Multiflori Caulis in Improving Depressive Disorder in Mice via Network Pharmacology Combined with Ultra-High Performance Liquid Chromatography Coupled with Quadrupole Exactive Orbitrap Mass Spectrometer

BACKGROUND AND OBJECTIVE

Depressive disorder (DD) is a common chronic and highly disabling disease. Polygoni Multiflori Caulis (PMC), a traditional Chinese medicine, has been listed in the 2020 edition of the Chinese Pharmacopoeia. Here, the antidepressant effects and mechanisms of PMC were explored for the first time.

METHODS

We observed the safety of PMC at a 10-fold clinically equivalent dose. Depressed mice were induced by chronic unpredictable mild stress (CUMS) and were used to evaluate the antidepressant effects of PMC via the sucrose preference test and the tail suspension test. The composition of PMC was identified by ultra-high performance liquid chromatography coupled with quadrupole exactive orbitrap mass spectrometer, and the active components, important targets, and potential mechanism of PMC in DD treatment were predicted via network pharmacology. Investigation included active compounds and DD-related targets screening, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation, PMC-compound-target-pathway-DD network construction, and Molecular docking.

RESULTS

In the safety evaluation of PMC, no toxic side effects or deaths occurred. There were no significant differences in liver function (ALT, AST, and TP; P > 0.05) and kidney function (BUN, CRE, and UA; P > 0.05) in each group of mice. Compared to the control group, the model group of mice showed significantly decreased sucrose preference and significantly increased immobility time (P < 0.01 or P < 0.05). Compared with the model group, the mice in the PMC low, medium, and high dose groups showed a significant decrease in immobility time and a significant increase in sucrose preference. In the PMC-Compound-Target-Pathway-DD network, 54 active compounds, 83 common targets, and 13 major signaling pathways were identified for the treatment of DD. Molecular docking verified that the active compounds could effectively bind with the hub targets.

CONCLUSION

PMC is a relatively safe antidepressant herbal medicine with its potential mechanism involving multiple compounds, targets, and pathways.

Usnea improves high-fat diet- and vitamin D3-induced atherosclerosis in rats by remodeling intestinal flora homeostasis

Background: Usnea has various pharmacological properties, including anti-inflammatory, antitumor, antioxidant, antiviral, and cardiovasculoprotective effects. Aim of the study: To investigate the potential mechanisms underlying the anti-atherosclerosis (AS) activity of Usnea ethanol extract (UEE) via the regulation of intestinal flora. Materials and Methods: The chemical composition of UEE was determined using ultra-performance liquid chromatography with quadrupole exactive orbitrap mass spectrometry (UPLC-Q-EOMS). Thirty-six male Sprague-Dawley rats were divided into six groups. A high-fat diet and intraperitoneal vitamin D3 injections were used to establish a rat model of AS. After 4 weeks of treatment with UEE, hematoxylin-eosin staining was performed to evaluate the pathomorphology of the aorta, liver, and colon. The composition and diversity of the rat intestinal flora were determined using high-throughput 16S rRNA sequencing. Enzyme-linked immunosorbent assays were used to measure the levels of plasma trimethylamine oxide (TMAO), serum bile acid (BA), total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). The protein expression of cholesterol 7α-hydroxylase (CYP7A1) and flavin monooxygenase 3 (FMO3) in the liver and zonula occludens-1 (ZO-1) and occludin in colon tissue was detected via western blotting. Results: Forty-four compounds were identified in UEE. In the rat model of AS, UEE significantly prevented calcium deposition; decreased the serum levels of TC, TG, LDL-C, LPS, TNF-α, and IL-6; and increased the serum level of HDL-C. Additionally, all UEE dosages decreased the relative abundance of Verrucomicrobiota while increased that of Bacteroidetes. FMO3 protein expression and TMAO levels decreased, whereas CYP7A1 protein expression and BA levels increased. The absorption of intestinal-derived LPS was minimized. Furthermore, the protein expression of ZO-1 and occludin was upregulated. Conclusion: UEE ameliorated AS. The underlying mechanism was the reversal of imbalances in the intestinal flora by Usnea, thereby inhibiting calcium deposition, abnormal lipid metabolism, and inflammatory response.

Antidepressant Effects and Mechanisms of the Total Iridoids of Valeriana jatamansi on the Brain-Gut Axis

Valeriana jatamansi is widely used in Chinese folk medicine and contains iridoids as important active ingredients. The brain-gut axis describes a complex bidirectional system between the central nervous system and the gastrointestinal tract. Herein, we evaluated the antidepressant effects of total iridoids of Valeriana jatamansi (TIV) and preliminarily investigated the effects of gut microbiota on their antidepressant effects using a chronic, unpredictable mild-stress mouse model. Mice were given 5.7, 11.4, or 22.9 mg/kg TIV for 1 week. Fluoxetine (2.6 mg/kg) served as a positive control. Body weight was measured, and behavioral tests including SPT and TST were applied. Colon pathology was assessed through hematoxylin-eosin staining. Additionally, levels of serotonin (5-hydroxytryptamine, 5-HT), norepinephrine (NE), substance P (SP) and corticotropin-releasing factor (CRF) in the hippocampus and colon were measured by ELISA. In addition, 16SrRNA gene sequencing was performed to explore changes in intestinal microbiota richness and diversity. Our results demonstrated that the model group showed significant depression-like behavior, while the fluoxetine group showed improved depression-like symptoms; after administration, TIV increased body weight, sucrose solution consumption, and ameliorated depression-like behaviors. The overall cell degeneration in colons also improved. In addition, TIV modulated the levels of 5-HT, NE, SP, and CRF expression in the hippocampus and colon. The diversity and richness of gut microbes increased compared to the model group. We therefore conclude that the antidepressant effects of TIV may be related to gut flora structures and regulation of 5-HT, NE, SP, and CRF in the brain and intestine.

U. diffracta extract mitigates high fat diet and VD3-induced atherosclerosis and biochemical changes in the serum liver and aorta of rats

BACKGROUND AND AIMS

Usnea diff ;racta Vain. (U. diffracta) belonging to the Usnea genus, is widely used as a folk medicine for the treatment of ulcer, abdominal pain, diarrhea, malaria and so on. However, the antiatherogenic effect of U. diffracta has not yet been reported. This study aims to investigate the antiatherogenic effects of the ethanol extract of U. diffracta and its mechanism.

METHOD

A high fat diet and VD3 were used to establish the atherosclerotic rat model, with 0.004 g/kg/d of simvastatin as a positive control, fed with 0.7, 1.4, and 2.8 g/kg/d of Usnea ethanol extract for 21 days. The blood, liver, and aorta samples from each rat were collected after the last administration. Pharmacodynamic effects were evaluated. The inflammation related factors, the gene expressions of Toll-like receptor 5 (TLR5), myeloid differentiating factor 88 (MyD88), and nuclear factor-κB (NF-κB) were detected.

RESULTS AND CONCLUSIONS

Compared with the model group, simvastatin and ethanol extract of U. diffracta can significantly reduce the serum levels of triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), Ca²⁺, AST, ALT, the liver contents of total cholesterol (TC), TG, AI and liver index, as well as significantly increase the contents of high-density lipoprotein cholesterol (HDL-C) both in serum and liver (p < 0.01 or p < 0.05). The serum level of ox-LDL can be significantly reduced by simvastatin, low and medium U. diffracta ethanol extract doses (p < 0.01). In addition, simvastatin and low dosage of U. diffracta ethanol extract can significantly reduce the liver content of LDL-C (p < 0.01). U. diffracta ethanol extract shows a positive antiatherogenic effect. Furthermore, the mechanism may be related to promoting the expression of serum IL-10 and inhibition of TLR5/NF-κB signaling pathway.

H2AX phosphorylation in response to DNA double-strand break formation during bystander signalling: effect of microRNA knockdown

Upon DNA double-strand break (DSB) formation, hundreds of H2AX molecules in the chromatin flanking the break site are phosphorylated on serine residue 139, termed gamma-H2AX, so that virtually every DSB site in a nucleus can be visualised within 10 min of its formation using an antibody to gamma-H2AX. One application of this sensitive assay is to examine the induction of DNA double-strand damage in subtle non-targeted cellular effects such as the bystander effect. Here whether microRNA (miRNA) serve as a primary signalling mechanism for bystander effect propagation by comparing matched human colon carcinoma cell lines with wild-type or depleted levels of mature miRNAs was investigated. No major differences were found in the levels of induced gamma-H2AX foci in the tested cell lines, indicating that though miRNAs play a role in bystander effect manifestation, they appear not to be the primary bystander signalling molecules in the formation of bystander effect-induced DSBs.

Binding of the human nucleotide excision repair proteins XPA and XPC/HR23B to the 5R-thymine glycol lesion and structure of the cis-(5R,6S) thymine glycol epimer in the 5'-GTgG-3' sequence: destabilization of two base pairs at the lesion site

The 5R thymine glycol (5R-Tg) DNA lesion exists as a mixture of cis-(5R,6S) and trans-(5R,6R) epimers; these modulate base excision repair. We examine the 7:3 cis-(5R,6S):trans-(5R,6R) mixture of epimers paired opposite adenine in the 5′-GTgG-3′ sequence with regard to nucleotide excision repair. Human XPA recognizes the lesion comparably to the C8-dG acetylaminoflourene (AAF) adduct, whereas XPC/HR23B recognition of Tg is superior. 5R-Tg is processed by the Escherichia coli UvrA and UvrABC proteins less efficiently than the C8-dG AAF adduct. For the cis-(5R, 6S) epimer Tg and A are inserted into the helix, remaining in the Watson–Crick alignment. The Tg N3H imine and A N⁶ amine protons undergo increased solvent exchange. Stacking between Tg and the 3′-neighbor G•C base pair is disrupted. The solvent accessible surface and T₂ relaxation of Tg increases. Molecular dynamics calculations predict that the axial conformation of the Tg CH₃ group is favored; propeller twisting of the Tg•A pair and hydrogen bonding between Tg OH6 and the N7 atom of the 3′-neighbor guanine alleviate steric clash with the 5′-neighbor base pair. Tg also destabilizes the 5′-neighbor G•C base pair. This may facilitate flipping both base pairs from the helix, enabling XPC/HR23B recognition prior to recruitment of XPA.

Repair of thymine glycol by hNth1 and hNeil1 is modulated by base pairing and cis-trans epimerization

Oxidation of thymine yields 5,6-dihydroxy-5,6-dihydrothymine (thymine glycol. Tg) which, as cis 5S,6R and 5R,6S 2'-deoxyribonucleoside diastereoisomers (dTg1, dTg2), are in equilibrium with their trans 5S,6S and 5R,6R epimers. The stereoselective excision of Tg from DNA by the mammalian orthologs of E. coli DNA N-glycosylase/AP lyases Nth and Nei was reported using substrates in which Tg opposed adenine. Since we showed that Tg is the major product of oxidation of 5-methylcytosine, we asked if the opposing purine influenced stereospecific enzymatic excision. The human ortholog hNth1 released Tg2 much more rapidly than Tg1 regardless of the opposing purine. In contrast, hNeil1 released Tg non-stereoselectively, but the rate of excision was much greater when Tg opposed guanine. Remarkably, the kinetics of excision of Tg by hNth1 and hNeil1 were biphasic, describing a double exponential curve which yielded two rate constants. We suggest that the greater rate constant describes the rate of enzymatic excision of Tg. The smaller rate constant represents the equilibrium constant for the cis and trans epimerization of dTg1 and dTg2 in high molecular weight DNA. Thus, only one of the epimers of dTg1 and dTg2 are enzymatically processed but it is not yet known whether it is cis or trans. Thus, base excision repair of Tg in mammals is mediated by at least two DNA N-glycosylase/AP lyases which are affected by the nature of the diastereoisomer of dTg, the rate of cis-trans epimerization of each diastereoisomer, and the nature of the opposing purine.

Substrate specificity of human endonuclease III (hNTH1). Effect of human APE1 on hNTH1 activity

Base excision repair of oxidized pyrimidines in human DNA is initiated by the DNA N-glycosylase/apurinic/apyrimidinic (AP) lyase, human NTH1 (hNTH1), the homolog of Escherichia coli endonuclease III (Nth). In contrast to Nth, the DNA N-glycosylase activity of hNTH1 is 7-fold greater than its AP lyase activity when the DNA substrate contains a thymine glycol (Tg) opposite adenine (Tg:A) (Marenstein, D. R., Ocampo, M. T. A., Chan, M. K., Altamirano, A., Basu, A. K., Boorstein, R. J., Cunningham, R. P., and Teebor, G. W. (2001) J. Biol. Chem. 276, 21242-21249). When Tg is opposite guanine (Tg:G), the two activities are of the same specific activity as the AP lyase activity of hNTH1 against Tg:A (Ocampo, M. T. A., Chaung, W., Marenstein, D. R., Chan, M. K., Altamirano, A., Basu, A. K., Boorstein, R. J., Cunningham, R. P., and Teebor, G. W. (2002) Mol. Cell. Biol. 22, 6111-6121). We demonstrate here that hNTH1 was inhibited by the product of its DNA N-glycosylase activity directed against Tg:G, the AP:G site. In contrast, hNTH1 was not as inhibited by the AP:A site arising from release of Tg from Tg:A. Addition of human APE1 (AP endonuclease-1) increased dissociation of hNTH1 from the DNA N-glycosylase-generated AP:A site, resulting in abrogation of AP lyase activity and an increase in turnover of the DNA N-glycosylase activity of hNTH1. Addition of APE1 did not abrogate hNTH1 AP lyase activity against Tg:G. The stimulatory protein YB-1 (Marenstein et al.), added to APE1, resulted in an additive increase in both activities of hNTH1 regardless of base pairing. Tg:A is formed by oxidative attack on thymine opposite adenine. Tg:G is formed by oxidative attack on 5-methylcytosine opposite guanine (Zuo, S., Boorstein, R. J., and Teebor, G. W. (1995) Nucleic Acids Res. 23, 3239-3243). It is possible that the in vitro substrate selectivity of mammalian NTH1 and the concomitant selective stimulation of activity by APE1 are indicative of selective repair of oxidative damage in different regions of the genome.

Targeted deletion of mNth1 reveals a novel DNA repair enzyme activity

DNA N-glycosylase/AP (apurinic/apyrimidinic) lyase enzymes of the endonuclease III family (nth in Escherichia coli and Nth1 in mammalian organisms) initiate DNA base excision repair of oxidized ring saturated pyrimidine residues. We generated a null mouse (mNth1(-/-)) by gene targeting. After almost 2 years, such mice exhibited no overt abnormalities. Tissues of mNth1(-/-) mice contained an enzymatic activity which cleaved DNA at sites of oxidized thymine residues (thymine glycol [Tg]). The activity was greater when Tg was paired with G than with A. This is in contrast to Nth1, which is more active against Tg:A pairs than Tg:G pairs. We suggest that there is a back-up mammalian repair activity which attacks Tg:G pairs with much greater efficiency than Tg:A pairs. The significance of this activity may relate to repair of oxidized 5-methyl cytosine residues (5meCyt). It was shown previously (S. Zuo, R. J. Boorstein, and G. W. Teebor, Nucleic Acids Res. 23:3239-3243, 1995) that both ionizing radiation and chemical oxidation yielded Tg from 5meCyt residues in DNA. Thus, this previously undescribed, and hence novel, back-up enzyme activity may function to repair oxidized 5meCyt residues in DNA while also being sufficient to compensate for the loss of Nth1 in the mutant mice, thereby explaining the noninformative phenotype.

Stimulation of human endonuclease III by Y box-binding protein 1 (DNA-binding protein B). Interaction between a base excision repair enzyme and a transcription factor

Human endonuclease III (hNth1) is a DNA glycosylase/apurinic/apyrimidinic (AP) lyase that initiates base excision repair of pyrimidines modified by reactive oxygen species, ionizing, and ultraviolet radiation. Using duplex 2'-deoxyribose oligonucleotides containing an abasic (AP) site, a thymine glycol, or a 5-hydroxyuracil residue as substrates, we found the AP lyase activity of hNth1 was 7 times slower than its DNA glycosylase activity, similar to results reported for murine and human 8-oxoguanine-DNA glycosylase, which are also members of the endonuclease III family. This difference in rates contrasts with the equality of rates found in Escherichia coli and Saccharomyces cerevisiae endonuclease III homologs. A yeast two-hybrid screen for potential modulators of hNth1 activity revealed interaction with the damage-inducible transcription factor Y box-binding protein 1 (YB-1), also identified as DNA-binding protein B (DbpB). The in vitro addition of His(6)YB-1 to hNth1 increased the rate of DNA glycosylase and AP lyase activity. Analysis revealed that YB-1 affects the steady state equilibrium between the covalent hNth1-AP site Schiff base ES intermediate and the noncovalent ES intermediate containing the AP aldehydic sugar and the epsilon-amino group of the hNth1 active site lysine. This equilibrium may be a checkpoint in modulating hNth1 activity.

Isolation and identification of xylitol-producing yeasts from agricultural residues

Selected yeast strains isolated from corn silage and viticulture residues were screened for their capacities to convert D-xylose into xylitol A conventional TLC was adapted for easy determination of xylose and xylitol in the culture supernatant solutions. This technique is suitable for the first steps of a screening program to select xylitol-producing yeasts from natural environments. Candida tropicalis ASM III (NRRL Y-27290), isolated from corn silage, appears to be a promising strain for xylitol production with a high yield (0.88 g xylitol per g of xylose consumed).

Serum testosterone:dihydrotestosterone ratio and CA 19-9 in the diagnosis of pancreatic cancer

The testosterone:dihydrotestosterone ratio (T:DHT) and the antigenic marker CA 19-9 were studied in the serum of 21 male patients with pancreatic cancer and 62 controls with other gastrointestinal malignancies or benign pancreatobiliary disease. Specificity of the T:DHT ratio was 98%, significantly better than the specificity of CA 19-9 at both a 37 U/ml cutoff level (61%) and at 100 U/ml (79%). Sensitivity of the T:DHT ratio was 67%, and that of CA 19-9, 71% and 90% at the upper and lower cutoff levels, respectively. False-negative results of the T:DHT ratio were found predominantly in cases of advanced pancreatic cancer, whereas all four stage I patients had an abnormal (less than 5) T:DHT ratio. These results suggest that the T:DHT ratio is a useful marker for pancreatic cancer in males. It can be used alone or in combination with CA 19-9, and should be further evaluated in the differential diagnosis of patients with the early stages of this disease.

Pancreatic cancer and androgen metabolism: high androstenedione and low testosterone serum levels

Serum androstenedione and testosterone levels were measured in 39 male patients with pancreatic cancer, and compared with the values obtained from 37 male patients with chronic pancreatitis or benign obstructive jaundice, and with those from 36 male patients with other gastrointestinal malignancies. Mean androstenedione values were significantly higher in the pancreatic cancer patients when compared to both control groups, and mean testosterone levels were significantly lower. The testosterone/androstenedione ratio was calculated and was also found to be significantly lower in the patients with pancreatic cancer. There was no difference in this ratio or in the androstenedione or testosterone levels when comparing both control groups. In two patients with stage I pancreatic cancer, serum androstenedione and testosterone levels were significantly altered, and returned to normal values after successful resection. These results confirm previous findings indicating that there is significant derangement in the androgen profile of patients with pancreatic cancer.

Adverse reactions to furazolidone and other drugs. A comparative review

Furazolidone is a synthetic nitrofuran with a broad spectrum of antimicrobial action and has been widely used in the treatment of gastrointestinal infections. This article reviews the adverse reactions to furazolidone reported in the world literature. Of 10,443 adults and children who were treated with the drug, approximately 8.3% (864) experienced such reactions. Because some of these patients had more than 1 adverse reaction, 1178 reactions were reported in these studies. Nausea with vomiting, the commonest adverse reaction, was reported by 51% of the 864 patients who experienced adverse reactions. The authors compare the adverse reactions to furazolidone with those reported for other antimicrobial and antiprotozoal drugs that are frequently used to treat gastrointestinal infections.

Low serum testosterone/dihydrotestosterone ratio in patients with pancreatic carcinoma

Serum testosterone, its metabolite 5 alpha-dihydrotestosterone, and the testosterone/dihydrotestosterone ratio were investigated in 22 male patients with proven pancreatic cancer, and compared with values from male patients with chronic pancreatitis (n = 21) and with nonpancreatic gastrointestinal tumors (n = 19). Testosterone and the testosterone/dihydrotestosterone ratio were significantly lower (p less than 0.001) in the pancreatic cancer group when they were compared with the other two groups. There was no significant difference in the dihydrotestosterone values between cancer groups. A testosterone/dihydrotestosterone ratio of less than 5 clearly distinguished most of the patients (20/22) with cancer of the pancreas from those with other tumors or chronic pancreatitis. The results suggest an alteration in the serum androgen profile in these patients. Therefore, the testosterone/dihydrotestosterone ratio could be a useful marker in the diagnosis of pancreatic carcinoma in male patients.

Self-priming effect of luteinizing hormone-human chorionic gonadotropin (hCG) upon the biphasic testicular response to exogenous hCG. I. Serum testosterone profile

The present study was conducted to investigate whether the early (2-8 h) testicular response to a single dose of exogenous hCG depends on previous exposure to LH activity. Four different groups of subjects were studied: 1) four normal adult men [Tanner stage-G5 (T-G5)] and one late pubertal subject (T-G4); 2) normal prepubertal (T-G1) and early- and midpubertal boys (T-G2 and T-G3) (n = 4-6 each); 3) five patients with hypogonadotropic hypogonadism (HH); and 4) two patients with the complete form of the androgen insensitivity syndrome. Each subject received an im injection of hCG (40 IU/kg) on day 1 and blood samples were drawn before and 1-8, 24, 48, and 72 h after injection. At 96 h, a second dose of hCG was given (80 IU/kg) and blood samples were obtained at the same times as after the first hCG dose. Serum testosterone (T) was measured by RIA. The first dose of hCG evoked a biphasic response of serum T in groups T-G2 to T-G5 as well as in the two patients with the complete form of the androgen insensitivity syndrome. The early peak was at 2-7 h, whereas the late T peak was at 48-72 h after injection. In T-G1 children and in patients with HH, the early response did not occur [T-G1, from 129 +/- 43 (SEM) to 288 +/- 127 pg/ml (P greater than 0.05); HH, 79 +/- 18 to 107 +/- 12 (P greater than 0.05) pg/ml], and the late peak was attenuated as compared with the pubertal boys. There were not significant differences in the responses of the T-G1 and the HH groups. After the second dose, all groups had biphasic T responses, although they varied in magnitude. These results demonstrate that previous exposure to LH activity is an obligatory prerequisite for the early peak of the hCG-mediated biphasic testicular response, and that a single dose of hCG has a priming effect that is sufficient to ensure a biphasic response to a second dose of hCG given 96 h later.