Competitive protein-binding radioassay of corticosterone in the plasma of the frog, Rana esculenta L.
Leboulenger, F.; Trochard, M.C.; Morin, J.P.; Dupont, W.; Vaudry, H.; Vaillant, R.
Journal de Physiologie 73(1): 73-83
1977
ISSN/ISBN: 0021-7948 PMID: 301934 Document Number: 114401
Plasma corticosterone levels were measured in the plasma of the edible frog, R. esculenta, by a competitive protein-binding radioassay method using baboon plasma as CBG [corticosteroid-binding globulin] source. This technique was sensitive enough to make the assessment of corticosterone levels in 50 .mu.l plasma samples possible. The assay sensitivity threshold reached 0.5 ng/tube and the corticosterone rate assessment was correct between 0-5 ng. The specificity was tested, using 12 different steroids; baboon CBG had very slight avidity for aldosterone, the 2nd circulating steroid in frog plasma. Plasma corticosterone underwent seasonal variations. Plasma corticosterone levels, in animals captured in nature during Feb. and June, were 1.51 .+-. 0.06 .mu.g/100 ml (n = 60) and 2.76 .+-. 0.14 .mu.g/100 ml (n = 36), respectively. It appeared that the interrenal gland of the frog was not totally dependent on pituitary ACTH, since total hypophysectomy reduced, but did not suppress, corticosterone secretion.