AIM To evaluate bioavailability, biocompa- tibility and biodegradability of an injectable microsphere sustained release preparation of naltrexone(NTX) in 4 dogs. METHODS Pharmacokinetic data of NTX and remained NTX in microspheres in injection site were studied using high performance liquid chromatography(HPLC)-electrochemical detection with naloxone(NLX) as internal standard. Biocompatibility of the microspheres was assayed by histological examination. RESULTSPharmacokinetics of NTX after an intramuscular dose of 0.5 or 1.0 mg*kg-1 NTX indicated a plasma clearance range of 0.66 to 0.73 L*min-1 and a t1/2β range of 60.0 to 67.2 min. After a 1-week washout period without medication, NTX microspheres injection period about 4 weeks followed. After injection of 1.0 g of microspheres containing (296.5±2.1)mg of NTX, mean blood concentrations of NTX exceeded 1 μg*L-1 for 26-28 d, and cmax per dose (mg*kg-1) was only 1% of that after NTX dosing. It was estimated that approximately (93.0±4.1)% of the administered dose was absorbed after microspheres injection in 4 dogs. There were no serious adverse effects other than light tissue irritation. CONCLUSIONThis NTX microspheres preparation provides a safe, complete and sustained release of the drug for about one month.

Objective? To?Study?the?changes?of?short-chain?acyl-CoA?dehydrogenase?(SCAD)?in?heart?failure?(HF)?after?myocardial?infarction?(MI),?and?the?effect?of?aerobic?exercise?on?SCAD.? Methods? Healthy?male?Sprague-Dawley?(SD)?rats?were?divided?into?sham?operation?group?(Sham?group),?sham?operation?swimming?group?(Sham+swim?group),?HF?model?group?(LAD?group)?and?HF?swimming?group?(LAD+swim?group)?by?random?number?table?method,?with?9?rats?in?each?group.?The?left?anterior?descending?branch?of?coronary?artery?(LAD)?was?ligated?to?establish?a?rat?model?of?HF?after?MI.?In?Sham?group,?only?one?loose?knot?was?threaded?under?the?left?coronary?artery,?and?the?rest?operations?were?the?same?as?those?in?LAD?group.?Rats?in?Sham+swim?group?and?LAD+swim?group?were?given?swimming?test?for?1?week?after?operation?(from?15?minutes?on?the?1st?day?to?60?minutes?on?the?5th?day).?Then?they?were?given?swimming?endurance?training?(from?the?2nd?week?onwards,?60?minutes?daily,?6?times?weekly,?10?weeks?in?a?row).?Tail?artery?systolic?pressure??(SBP)?was?measured?before?swimming?endurance?training?and?every?2?weeks?until?the?end?of?the?10th?week.?Ten?weeks?after?swimming?training,?echocardiography?was?performed?to?measure?cardiac?output?(CO),?stroke?volume?(SV),?left?ventricular?ejection?fraction?(LVEF),?shortening?fraction?(FS),?left?ventricular?end-systolic?diameter?(LVESD),?left?ventricular?end-diastolic?diameter?(LVEDD),?left?ventricular?end-systolic?volume?(LVESV),?and?left?ventricular?end-diastolic??volume?(LVEDV).?Morphological?changes?of?heart?were?observed?by?Masson?staining.?Apoptosis?of?myocardial?cells?was?detected?by?transferase-mediated?deoxyuridine?triphosphate-biotin?nick?end?labeling?stain?(TUNEL)?and?apoptosis?index?(AI)?was?calculated.?Reverse?transcription-polymerase?chain?reaction?(RT-PCR)?and?Western?Blot?were?used?to?detect?the?mRNA?and?protein?expression?of?myocardial?SCAD?respectively.?In?addition,?the?enzyme?activity?of?SCAD,?the?content?of?adenosine?triphosphate?(ATP)?and?free?fatty?acid?(FFA)?in?serum?and?myocardium?were?detected?according?to?the?kit?instruction?steps.? Results? Compared?with?Sham?group,?Sham+swim?group?showed?SBP?did?not?change?significantly,?with?obvious?eccentric?hypertrophy?and?increased?myocardial?contractility,?and?LAD?group?showed?persistent?hypotension,?obvious?MI,?thinning?of?left?ventricle,?and?decreased?myocardial?systolic/diastolic?function.?Compared?with?LAD?group,?SBP,?systolic/diastolic?function?and?MI?in?LAD+swim?group?were?significantly?improved?[SBP?(mmHg,?1?mmHg?=?0.133?kPa):?119.5±4.4?vs.?113.2±4.5?at?4?weeks,?120.3±4.0?vs.?106.5±3.7?at??6?weeks,?117.4±1.3?vs.?111.0±2.3?at?8?weeks,?126.1±1.6?vs.?119.4±1.9?at?10?weeks;?CO?(mL/min):?59.10±6.31?vs.?33.19±4.76,?SV?(μL):?139.42±17.32?vs.?84.02±14.26,?LVEF:?0.523±0.039?vs.?0.309±0.011,?FS:?(28.17±2.57)%?vs.?(15.93±3.64)%,?LVEDD?(mm):?8.80±0.19?vs.?9.35±0.30,?LVESD?(mm):?5.90±0.77?vs.?7.97±0.60,?LVEDV?(μL):?426.57±20.84?vs.?476.24±25.18,?LVESV?(μL):?209.50±25.18?vs.?318.60±16.10;?AI:?(20.4±1.4)%?vs.?(31.2±4.6)%;?all?P??0.05).? Conclusion? The?expression?of?SCAD?in?HF?was?significantly?down-regulated,?and?the?expression?was?significantly?up-regulated?after?aerobic?exercise?intervention,?indicating?that?swimming?may?improve?the?severity?of?HF?by?up-regulating?the?expression?of?SCAD.