Dispersal of estradiol-17 beta from the site of injection in the pectoral muscles of Japanese quail

Exogenous estrogens, if given in sufficient quantity, stimulate vitellogenesis in the males of vitellogenic species. In the present study, ethanolic solutions of estradiol-17 beta (E2), labeled with 16-alpha-[125I]iodoestradiol ([125I]E2) or sodium iodide (Na125I), were injected into the pectoral muscles of male Japanese quail. The rate of dispersal of the estradiol from the site of injection was measured in vivo during 4 days. The curves of radioactivity appeared to be diphasic. The dose percentages forming the second phase of these curves and the half-time for the second phase were: for 16 mumol E2 ([125I]E2 label)/100 g body weight, 84.6% and 27.6 hr; for 6 pmol [125I]E2/100 g, 20.0% and 17.2 hr; for 16 mumol E2 (Na125I label)/100 g, 6.7% and 99.0 hr, and for Na125I, 6.1% and 83.1 hr. Thus, in male quail the estradiol-induced stimulation of vitellogenesis apparently resulted from a continuing hormonal pressure on the liver during the period of study and not from a rapid flow of E2 to the liver shortly after injection.