ABSTRACT
Most studies related to research on steroids in main edible tissues (muscle, liver or kidney) have focused on measurement of parent or major metabolite residues. In order to evaluate the estradiol content in bovine edible tissues, a multi-step extraction procedure was developed in conjunction with parallel metabolism studies of [14C]-17beta-estradiol in cattle (1-2). Various classes of free estradiol and conjugates were separated: estradiol -17beta and -17alpha, estradiol-17-fatty acid esters, estradiol 17-glycoside, estradiol 3-glucuronide, estradiol-17-glycoside and 3- glucuronide (diconjugates) were separated. No sulphates conjugated forms have been found at the detection level of the method. The quantification was realized by calibration with deuterated 17beta -estradiol -d3 standard and was validated at the ng x kg(-1) (ppt) level. Muscle, liver, kidney and fat samples from control or Revalor S single (licensed implantation) or multi-implanted steers have been assayed. The results show a wide variation between animals, but both the highest value and the mean of total estradiol content in each group proportionally increase from untreated to multi-implanted animals. In accordance with international rules, a calculation of the daily food supply of estradiol by such edible tissues in comparison with the acceptable daily intake was performed.
