title: In vivo patterns of circulating testosterone following castration and intramuscular testosterone propionate injections of adult male rats.
abstract: In vivo patterns of circulating testosterone (T) were investigated in castrated and in intact male rats following a single intramuscular injection of 1mg testosterone propionate (TP). In addition, the in vivo clearance pattern of T was investigated following castration. The injection of TP into intact rats resulted in a rapid, statistically significant increase in circulating T which lasted for 12h and returned to normal by 24h post-injection. Circulating T decreased to nondetectable levels by 6h following orchiectomy. Injection of TP into castrated rats caused a rapid increase in circulating T which reached highest levels 60 min after administration. The concentrations of T in TP-treated orchiectomized rats remained elevated for 12h with a gradual decline which persisted for the experimental period of 6 days post-injection and provided moderate maintenance of sex accessory organ weights. TP injections increased circulating T levels in both groups of rats, but the magnitude of elevation was greater in intact animals where the normal T diurnal variations were disturbed. The elevation in circulating T persisted longer in the castrate-TP-treated animals than in intact animals, suggesting a difference in clearance, distribution and metabolism of T in orchiectomized rats.
mesh_terms: D000818:Animals; D002369:Castration; D007273:Injections, Intramuscular; D007700:Kinetics; D008297:Male; D009929:Organ Size / Q000187:drug effects; D011467:Prostate / Q000033:anatomy & histology; D011863:Radioimmunoassay; D051381:Rats; D012669:Seminal Vesicles / Q000033:anatomy & histology; D013739:Testosterone / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology
chemical_list: D013739:Testosterone