[Feasibility and efficacy of pre-management of superior laryngeal artery in endoscopic surgery for hypopharyngeal cancer]

Objective: To explore the feasibility and efficacy for the dissection and ligation of the superior laryngeal artery in endoscopic surgery for hypopharyngeal cancer. Methods: Eight cadaveric heads were selected, and the laryngopharynxes were harvested. The positions of the superior laryngeal arteries entering the larynxes were dissected and observed under endoscopic vision, and their anatomical characteristics were summarized. Twenty-nine patients (all were male, aged 39-74 years old) with hypopharyngeal cancer who underwent transoral endoscopic surgery at the Department of Otorhinolaryngology Head and Neck Surgery of the Second Xiangya Hospital, Central South University from January 2018 to December 2019 were selected, and the patients were randomly divided into two groups by drawing lots, namely, the superior laryngeal artery was actively dissected and occluded during surgery in observation group (n=15) or not in control group (n=14). The differences in surgical time, bleeding volume, postoperative complications, and postoperative disease-free survival rate were compared between the two groups. Statistical analysis was conducted using SPSS 25.0 software. Results: The entry point of the superior laryngeal artery into the larynx was approximately at the level of the superior edge of the thyroid cartilage, and entered the larynx at the posterior one-third of the lateral wall of the pyriform fossa. The superior laryngeal artery might be determined through endoscopic exploration in all patients of observation group. The endoscopic surgery time [(40.00±7.56) minutes] and intraoperative bleeding volume [(24.00±8.28) ml] in the observation group were respectively less than those [(48.57±14.06) minutes and (42.86±15.41) ml] in the control group, and the differences were statistically significant (t=-2.064, P=0.049; t=-4.064, P=0.001). There was no case with postoperative bleeding in the observation group, but with one case of postoperative bleeding in the control group. Total disease free survival rate was 86.2% and there was no significant difference in disease free survival rates between the two groups during a follow-up period of at least 36 months (P=0.986). Conclusion: Dissection of the superior laryngeal artery during endoscopic surgery for hypopharyngeal cancer is feasible, and pre-management and occlusion of the superior laryngeal artery can effectively reduce intraoperative bleeding.

Efficacy and safety of a 14-day modified concomitant therapy for refractory Helicobacter pylori infection: a pilot study

BACKGROUND AND AIM

After three treatment failures, Helicobacter pylori infection is deemed refractory as antibiotic treatment options become significantly limited. This study evaluated the efficacy and safety of a 14-day modified concomitant therapy for managing refractory H. pylori infection.

METHODS

Patients who had failed to respond to three or more rounds of H. pylori therapies were recruited for this study. They received a 14-day modified concomitant therapy, including esomeprazole 40 mg, amoxicillin 1000 mg, and furazolidone 100 mg twice daily and tetracycline 500 mg four times daily. Demographic data, adverse events, and patient compliance were recorded. The presence of H. pylori was reevaluated 6 weeks following treatment. Eradication rate was assessed as the primary outcome.

RESULTS

Overall, 59 participants received the 14-day modified concomitant therapy. In the intention-to-treat and per-protocol analyses, the eradication rate was 84.7% (50/59) and 89.3% (50/56), respectively. H. pylori was successfully isolated from 75.0% (12/16) of patients. The resistance rate of H. pylori to metronidazole, levofloxacin, and clarithromycin was 91.7% (11/12), 58.3% (7/12), and 50.0% (6/12), respectively. Resistance to amoxicillin, furazolidone, or tetracycline was not observed. The frequency of adverse events was 35.6% (21/59), with no serious adverse events reported.

CONCLUSION

The 14-day modified concomitant therapy appears to be appropriate for refractory H. pylori infection and is particularly promising for the Chinese population. A randomized controlled trial is warranted to verify its efficacy, especially in the current environment of increasing antibiotic resistance.

[Application of supraclavicular fasciocutaneous island flap for reconstruction after removal of tumors in parotid and auricle area]

Objective: To evaluate the efficacy of supraclavicular fasciocutaneous island flap (SIF) for repairing the defect of parotid or auricle regions after tumor resection. Methods: From February 2019 to June 2021, 12 patients (11 males and 1 female, aged 54-77 years old), of whom 4 with parotid adenoid cystic carcinoma and 8 with auricular basal cell carcinoma underwent reconstruction surgery for postoperative defects in the parotid gland area and auricular area with SIF in the Department of Otorhinolaryngology Head and Neck Surgery, the Second Xiangya Hospital of Central South University and their clinical data were retrospectively analyzed. Size of the SIF, time for harvesting SIF, neck lymph node dissection and postoperative complications were recorded. Results: The flap areas were (6-9) cm × (8-13) cm, and the harvesting time for SIF ranged from 40 to 80 min, averaging 51.7 min. The donor sites were directly closed. All patients underwent ipsilateral levels Ⅰ-Ⅲ neck dissection, with 4 cases undergoing additional level Ⅳ neck dissection and 2 cases undergoing level Ⅳ-Ⅴ neck dissection. Of the 12 SIF, 10 were completely survival and 2 had flap arterial crisis with partial flap necrosis, in addition, 1 had donor site wound dehiscence. With follow-up of 10-42 months, there were no tumor recurrences in 10 patients, 1 patient was lost to follow-up at 10 months postoperatively, and 1 patient experienced local tumor recurrence at 11 months after surgery and died 15 months later. Conclusion: SIF is an easily harvested flap with good skin features matching the skin in parotid and auricle regions and less damage to donor site, and this flap has no need for microvascular anastomosis technique. SIF is feasible and effective for repairing defects in parotid and auricle area.

[Feasibility and efficacy of preserving internal branch of superior laryngeal nerve in endoscopic surgery for hypopharyngeal squamous cancer: an observational study]

Objective: This study was performed to investigate the feasibility of preservation of internal branch of superior laryngeal nerve(ibSLN) during transoral endoscopic surgery for hypopharyngeal squamous cancer(HSCC) and the influence on patient's swallowing function after operation. Methods: From May 2020 to June 2021, the data of 29 HSCC patients who required for transoral endoscopic surgery in the Department of Otorhinolaryngology Head and Neck Surgery, the Second Xiangya Hospital of Central South University were prospectively included, and the included patients were divided into two groups randomly by lottery. According to whether ibSLN was actively dissected during operation, they were divided into ibSLN preservation group (n=15) and control group (n=14, without ibSLN preservation). Operation time, intraoperative hemorrhage, intraoperative neck dissection, postoperative radiotherapy, postoperative recurrence within 1 year, retention and swallowing function, the recovery of oral soft diet and the quality of life were compared between two groups. SPSS 25.0 software was used for statistical analysis. Results: The study included 29 eligible patients, including 25 males and 4 females.The age ranged from 42 to 67 (56.07±5.93) years. There were no significant differences(P>0.05) between 2 groups in the following data,including age(t=-0.56), gender(χ2=0.01), TNM stage(T stageχ2=0.29, N stage χ2=0.02), pathological diagnosis(χ2=0.03), preoperative swallowing function(χ2=0.00) and M. D. Anderson Dysphagia Inventory(MDADI) score(global t=0.55, emotional t=0.16, functional t=0.60, physical t=0.64), operation time(t=1.62) and intraoperative hemorrhage(t=-1.46), intraoperative neck dissection(χ2=0.01), postoperative radiotherapy(χ2=0.32), postoperative recurrence within 1 year(P>0.050). The swallowing function was evaluated by water swallowing test after operation. The swallowing function of ibSLN preservation group was better than control group, and the difference between two groups was statistically significant on the 1st (χ2=4.44, P=0.035), 5th (χ2=4.24, P=0.039) and 7th (χ2=4.55, P=0.033) day after operation. On the 14th day after operation, the MDADI scores of patients in the ibSLN preservation group were higher than those in the control group in global (t=2.45, P=0.021), functional (t=2.54, P=0.017) and physical (t=2.24, P=0.034) dimensions, except for emotional dimension (t=1.89, P=0.070). The median time of oral soft diet(U=23.00, P<0.001), normal oral diet(U=21.00, P<0.001) and the nasogastric tube removal time (U=18.50, P<0.001) in ibSLN preservation group was 2 days, 5 days and 6 days respectively, earlier than that in control group, which had statistically significant difference. Conclusion: Our results show that it is feasible to preserve the ibSLN during HSCC transoral endoscopic surgery, which can achieve rapid recovery of postoperative swallowing function.

Protective effect of sonic hedgehog signaling pathway activation on acute myocardial infarction

To study changes in the sonic hedgehog (Shh) signaling pathway in acute myocardial infarction (AMI) and the protective effect of changes in Shh signaling pathway activity on AMI, specific pathogen-free (SPF) C57BL/6 mice were treated with left anterior descending (LAD) ligation to establish an AMI model. The samples were collected on the 1st, 3rd, 14th, and 21st days after AMI induction. After the operations, the mice were administered the Shh signaling pathway receptor agonist SAG1.3 (5 mg/kg/d) and antagonist SANT-1 (3.3 mg/kg/d) by intraperitoneal injection. The myocardial ischemia model was established by oxygen glucose deprivation (OGD) in vitro. The AMI mouse model and the in vitro OGD-induced myocardial ischemia model were established. The Smo agonist SAG1.3 was used to activate the Shh signaling pathway, thereby reducing the expression of Bcl-2 and Bax. The number of apoptotic cells was reduced. Administration of the antagonist SANT-1 inhibited Shh signaling pathway activity by increasing the expression of Bcl-2 and Bax, and the number of apoptotic cells increased. In conclusion, activation of the Shh signaling pathway improved cardiac functions and myocardial remodeling and reduced the apoptosis of myocardial cells.

[Analysis of 30 cases of inherited cardiac arrhythmia syndrome in children]

Objective: To analyze and summarize the diagnosis and treatment experience of common inherited cardiac arrhythmia syndrome in pediatric patients, and explore the most appropriate therapy. Methods: A retrospective review identified 30 pediatric cases (19 males, 11 females) diagnosed with long QT syndrome (LQTS), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), hypertrophic cardiomyopathy (HCM), arrhythmogenc right ventricular cardiomyopathy (ARVC) from January 2008 to December 2018 in the Pediatric Cardiology Department, Guangdong Provincial People's Hospital. Data obtained included the diagnosis, treatment and follow-up outcome. Results: The most common inherited cardiac arrhythmia syndromes were LQTS (n=14) including 1 case with epilepsy, CPVT (n=5), HCM (n=7), ARVC (n=1), and BrS (n=3). Twenty-seven cases were admitted to hospital due to syncope, whereas the remaining 3 cases of BrS had not presented with syncope before admission. The average onset age of inherited arrhythmia was (10.0±3.3) years. Genetic testing was performed on 20 patients. The median follow-up time was 40 months. Among 15 patients who underwent implantable cardioverter defibrillator (ICD) and survived, 2 patients had frequent ICD discharge. One patient underwent radiofrequency ablation, and the other one received left cardiac sympathetic denervation and an increased ICD defibrillation threshold, and the number of ICD discharge was significantly reduced. Among 10 patients who received drug therapy, 4 patients including two patients who discontinued treatment without advices died. Two patients whose parents refused treatment died, 1 case diagnosed with unexplained sudden cerebral death, and the remaining 2 cases without indication for drug therapy survived without any treatment. Conclusions: Mortality rate is high in pediatric patients with inherited cardiac arrhythmia and syncope. The therapeutic effect of drugs are not satisfactory, ICD implantation is the most effective treatment to prevent sudden cardiac death currently, but the postoperative frequent discharge should be brought to the forefront and handled in time.

[A long-term follow-up study of cardiac resynchronization therapy for children with right ventricle-paced heart failure]

Objective: To evaluate the long-term effects of cardiac resynchronization therapy (CRT) in children with right ventricle-paced heart failure. Methods: Five children with chronically right ventricular-paced heart failure underwent operation of upgrading to CRT in Guangdong Cardiovascular Institute between July 2009 to January 2015. The first time the patients were implanted with endocardial permanent pacemaker was (11.6±4.6) years old. The New York Heart Association (NYHA) functional classification, QRS duration, left ventricular end diastolic diameter (LVDd), left ventricular ejection fraction (LVEF), standard deviation of peak systolic time of left ventricular wall (TS-SD) and follow-up data were retrospectively analyzed. Comparison between pre-and post-operation was performed using paired t test. Results: CRT significantly improved the NYHA class to Ⅰ-Ⅱdegree, reduced the QRS duration ((126±9)vs. (182±21)ms, t=-7.480, P=0.002) and the Z-score of LVDd (2.8±1.1 vs. 4.7±0.9, t=-2.880, P=0.045), and increased the LVEF (43%±10% vs. 28%±6%, t=3.350, P=0.029). No significant difference was found regarding the TS-SD ((48±17)vs. (95±41)ms, t=-2.240, P=0.090) pre- and post-CRT. The longest follow-up period was 9 years. During follow-up, 1 case died of ventricular fibrillation 2 years after upgrading, and 2 cases underwent CRT replacement due to battery depletion 7.2 years and 5.8 years after upgrading, respectively. Conclusion: CRT could be considered for children with chronically right ventricular-paced heart failure and improve heart function significantly.

[Laparoscopic type C1 hysterectomy based on the anatomic landmark of the uterus deep vein and its branches for cervical cancer]

Objective: To introduce the laparoscopic type C1 hysterectomy based on the anatomic landmark of the uterus deep vein and its branched and to evaluate its feasibility and safety for cervical cancer and its effect to bladder function and to provide some reference to simplify the surgical procedures of laparoscopic type C1 hysterectomy. Methods: The clinicopathologic data of the patients with stage ⅠA2~ⅡB cervical cancer and who underwent the laparoscopic C1 hysterectomy based on anatomic landmark of the uterus deep vein and its branches between March 2010 and December 2015 was retrospectively analysed. Results: A total of 99 patients received laparoscopic type C1 hysterectomy based on the anatomic landmark of the uterus deep vein and its branches, in which 93 patients reserved unilateral or bilateral pelvic autonomic nerve successfully, the other 6 patients were transfered to receive type C2 hysterectomy due to adhesions, bleeding or the low possibility of curative resection. The failure rate of the surgery was 6.1% (6/99). The average age of these 93 patients was 44.4±8.2 years (range 25~61 years) and there was one case of stage ⅠA2, 84 stage ⅠB1, 2 stage ⅠB2, 5 stage ⅡA1 and 1 stage ⅡB. The number of patients with squamous cell carcinoma was 67, adenocarcinoma was 19, adenosquamous carcinoma was 3, small cell neuroendocrine carcinoma was 3 and mixed type was 1. The average operation time was 4.1±0.5 h, the average amount of intraoperative blood loss was 103.8±84.0 ml and the mean number of excisional pelvic lymph nodes was 29.7±8.9. There was no patient with positive parametrial margin, positive vaginal margin or intraoperative ureteral injury. The postoperative catheter extraction time was 20.3±8.4 d. The median follow-up time was 20 months (rang 5~44 months), the long-term bladder dysfunction rate was 8.6% (8/93). The numbers of locally uncontrolled and distantly metastasis case were both one and both patients died. The fatality rate were 2.2% (2/93). The two-year disease-free survival and overall survival rate were 97.6% and 96.2%, respectively. Conclusion: Laparoscopic type C1 hysterectomy based on the anatomic landmark of the uterus deep vein and its branches is a safe and feasible treatment method for cervical cancer and it provides a new approach for simplifying the surgical procedures of laparoscopic type C1 hysterectomy.

Treatment and outcome of Stage I Al squamous carcinoma of the cervix: a clinicopathologic study of 346 cases

OBJECTIVE

To analyze the clinicopathologic feature of Stage I A I squamous carcinoma of the cervix (SCC) and to explore the outcome of different surgical methods.

MATERIALS AND METHODS

Clinicopathological data of 346 cases with Stage I Al SCC diagnosed between November 2nd, 1995 and December 31st, 2011 were reviewed and analyzed.

RESULTS

As major diagnostic method, 44.5% (154/346) patients accepted cold knife conization (CKC), while 58.1% (201/346) patient took total hysterectomy (TH) as their final surgical methods. The trend in treatment methods from 1995 to 2011 revealed that increasing cases were treated with CKC, modified radical hysterectomy (MRH) obviously reduced, while the proportion treated by TH remained unchanged. Due to a small number of cases receiving vaginal trachelectomy (VT) and radical trachelectomy (RT), the authors did not find any obvious changes.

PROGNOSIS

The overall recurrence rate was 1.2% (4/346). The overall survival rates for CKC, VT, TH, MRH, and RT were 100%, 100%, 98.2%, 100%, and 100%, and the difference was not statistically significant (p = 0.819). The incidence rate of LVSI was 4.9% (17/346), the overall survival rates for patients with LVSI and without LVSI were 99.3% and 93.3%, respectively, and there was statistical difference between them (p = 0.003). Univariate analysis showed that only LVSI was an important predictor for survival (p = 0.030).

CONCLUSIONS

the treatments for Stage I Al SCC are becoming more conservative, and individualized therapy and more frequent surveillance should be administrated to those patients with LVSI.

Identification of natural recombinants derived from PCV2a and PCV2b

Porcine circovirus type 2 (PCV2) is considered to be the main pathogen in PC-associated diseases, and significantly affects the global pig-producing industry. PCV2 continuously evolves by point mutations and genome recombinations. In the present study, we aimed to further identify recombinant PCV2 strains. We used polymerase chain reaction to detect PCV2 in the carcasses of pigs with suspected infections from different regions of Guangdong Province in China. DNA was extracted from samples with confirmed infection and full- genome amplification, sequencing, phylogenetic tree construction, gene recombination detection, and sequence alignment were performed in gene recombination analysis. Our results show that recombination occurred between the strains SHC (DQ104421) and ZhuJi2003 (AY579893). The recombination resulted in three recombinants: GD003 (KM503044), GD005 (KM487708), and GD008 (KM487709). Further analyses revealed that these novel recombinants appeared to result from recombination between the PCV2a and PCV2b strains, with crossover regions located in ORF2. This study was a comprehensive analysis that used several different methods, which demonstrated that a cluster of PCV2 strains resulted from the same type of inter-genotypic recombination pattern, with a breakpoint in the structural protein coding region. The results of our study provide both information on the recombination mechanism and disease pathogenesis and useful data for the prevention of PCV2 in the swine industry.

Pathologic characteristics and prognosis of a rare advanced cervical cancer treated with radical surgery and radiotherapy

OBJECTIVE

To assess the prognosis of rare advanced.cervical carcinoma with post-radical-radiation surgery and to compare the clinic value between further surgery treatment group and non-surgery group after radical radiation therapy.

MATERIALS AND METHODS

From January 2002 to July 2010 there were 68 patients with advanced stage cervical carcinoma retrospectively analysed in Maternal and Child Health Hospital of Jiangxi Province. All patients were confirmed by histopathology before treatment, and clinical staging was based on updated 2009 FIGO staging. All patients were Stage Ib2 (local advanced) and more severe. There were 36 patients (29 adenocarcinoma (AC), six adenosquamous carcinoma (ASC), and one undifferentiated carcinoma) classified into observation group that was treated with radical radiation therapy + surgery (total hysterectomy + bilateral salpingo-oophorectomy); other 32 patients (26 AC, five ASC, and one undifferentiated carcinoma) classified into control group that was treated with radical radiation therapy with no further surgery. The radical radiation therapy included external-beam radiation and intracavitary therapy, standard point A dose added up to 85 Gy (these doses are recommended for most patients based on summation of conventional external-beam fractionation and low-dose rate 40-70 cGy/h brachytherapy equivalents), and 45-55 Gy was given to point B. All of the patients were followed up. The average follow-up time was 65.6 months and the survival rate between two groups were compared and analyzed whether there was residual lesion, metastasis, lymph vascular space invasion (LVSI) in the observation group.

RESULTS

In observation group there were 15 patients found positive. The positive rate was 41.7% (15/36), in which there nine cases with LVSI and residual foci, four cases with uterus invasion, and one case with only residual foci. Both of the two groups were followed up and the average follow-up time was 65.6 months (range 36-136). In observation group there were 25 cases that have survived until now and the average survival time was 66.6 months (range 36-136). Eleven patients died with an average survival time of 10.4 months (range 2-37). In control group there are 22 cases that survived until now (July 2013); the average survival time was 64.4 months (range 36-136). Ten patients died with an average survival time of 10.3 months (range 3-28). Three cases experienced serious complication in observation group and two cases in control group. There was no significant difference in survival time between the two groups.

CONCLUSION

Due to low efficacy results, post-radical-radiation surgery is not a feasible treatment regimen for rare advanced cervical carcinoma.

Prospective study of hTERC gene detection by fluorescence in situ hybridization (FISH) in cervical intraepithelial neoplasia 1 natural prognosis

OBJECTIVE

The aim of this study was to evaluate the prognostic significance of human chromosome telomerase gene (hTERC) overexpression in cervical intraepithelial neoplasia grade 1 (CIN1) natural prognosis.

MATERIALS AND METHODS

A total number of 2,499 women aged 30-49 years were screened in a population-based cervical cancer screening study from Jiangxi province rural sites. Pathology as the gold standard, 74 CIN1 patients first diagnosed by pathological examination were studied. They were observed by carrying the hybrid capture2 (HC2) and hTERC genetic testing to understand the baseline. All observed women accepted voluntary follow-up. Follow-up for the first time in the first 12 months after screening included hr-HPV HC-2 testing. The second follow-up after screening the first 24 months, included hr-HPV HC-2, colposcopy + pathological examinations.

RESULTS

Of the 74 CIN1 cases that were followed-up for 24 months, seven cases (9.5%) progressed; 25 cases (33.8%) persisted, and 42 patients (56.7%) regressed. There was significant difference between hTERC amplification positive and negative group (chi2 = 21.07, p < 0.001). The risk of CIN1 persistence and progression in positive group was 3.24 (1.96-5.37) times higher than that in negative group. There was significant difference between hr-HPV persist positive and turn to negative or persistent negative group (chi2 = 7.645, p = 0.006). There was significant difference between hTERC gene and the initial test of hr-HPV both positive and both negative group (chi2 = 4.544, p = 0.033).

CONCLUSION

There was a strong association between prevalence of hTERC gene overexpression and CIN1 natural prognosis. The follow-up results indicated that Hr-HPV required repeat testing and that there was significant difference between hr-HPV persistent positive and turn to negative/persistent negative group (chi2 = 7.645, p = 0.006). hTERC gene overexpression could prognoses cervical intraepithelial neoplasia 1 natural prognosis individually.

Comparison of the efficacy and complications of different surgical methods for cervical intraepithelial neoplasia

OBJECTIVE

The aim of this was study to offer some reference for the treatment of cervical intraepithelial neoplasia (CIN) by comparing complication rates and treatment failure rates of different surgical methods of CIN.

METHODS

1,256 cases of CIN diagnosed by punch biopsy and pathological confirmation of postoperative specimens between January 2002 and June 2007 were reviewed and analyzed, in which 74 cases underwent the loop electrosurgical excision procedure (LEEP), 869 patients adopted cold knife conization (CKC), 49 patients received vaginal enlarged amputation of cervix, and 264 patients accepted extrafascial hysterectomy. The chi-square test was used to compare the rate of complication and treatment failure of different surgical methods.

RESULTS

The rates of surgical complications for LEEP, CKC, vaginal enlarged amputation of the cervix and extrafascial hysterectomy were, respectively, 8.1% (6/74) 6.2% (54/869) 6.1% (3/49) and 2.3% (8/264), but this difference was not statistically significant. The treatment failure incidences for LEEP, CKC, vaginal enlarged amputation of cervix and external fascia hysterectomy were, respectively, 4.1% (3/74), 0.2% (2/869), 0.0% (0/49) and 0.4% (1/264). When comparing among the groups, the treatment failure incidence was higher in LEEP than that in CKC (p = 0.004) and extrafascial hysterectomy (p = 0.034); there was no statistically significant difference between CKC and extrafascial hysterectomy, and no significant difference was revealed between vaginal enlarged amputation of cervix and any other group.

CONCLUSION

LEEP, CKC, vaginal enlarged amputation of cervix and extrafascial hysterectomy are all secure and effective procedures for patients with CIN, and patients can make their own individual choice depending on different conditions.

Metabolism and pharmacokinetics of 24,25-dihydroxyvitamin D3 in the vitamin D3-replete rat

The time course of in vivo metabolism of 24,25-dihydroxyvitamin D3 in rats has been examined. Several tissues were surveyed in an effort to discover new metabolites of 24,25-dihydroxyvitamin D3 and to estimate the concentrations of previously identified metabolites. Rapidly growing male rats were dosed with 24,25-dihydroxyvitamin D3 orally until plasma concentrations of 24,25-dihydroxyvitamin D3 were at steady state. 24,25-Dihydroxyvitamin [3-3H]D3 was then administered. At 10 min and 1, 6, 15, 24, 96, and 192 h after dosing, the animals were killed, and plasma, liver, intestine, and bones were analyzed with a newly developed gradient straight-phase high performance liquid chromatography system. The high performance liquid chromatography system is capable of base-line resolution of most of the major vitamin D metabolites. 24,25-Dihydroxyvitamin D3 clearance from plasma, liver, and kidney but not intestine followed a two-compartment model. 24,25-Dihydroxyvitamin D3 disappeared from plasma with a half-life of 0.55 h (fast phase) and 73.8 h (slow phase). Only two lipid-soluble metabolites of 24,25-dihydroxyvitamin D3 were detected: 24-oxo-25-hydroxyvitamin D3 and 1,24,25-trihydroxyvitamin D3. These compounds circulate at very low concentrations in the plasma (50 pg/ml of plasma).