Chemical Determination of 17-Hydroxycorticosteroids in the Blood of Cattle and some Indications of its Physiological Significance

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Abstract
A method for the chemical determination of 17-hydroxycorticosteroids in the plasma of dairy cattle was developed and evaluated. The method employs the extraction of cold plasma by cold ethyl acetate and assay of the steroids by using the Porter-Silber color reaction. The efficiency of the extraction procedure was judged to be 81% as determined by calculating the recovery of steroid added to plasma. A mean increase of 120% in plasma 17-hydroxycorticosteroids was obtained 2 hours after the intramuscular administration of 600 Armour Veterinary Units of ACTH to 6 cows. Plasma 17-hydroxycorticosteroid values for 23 dry, pregnant cows ranged from 6.90 to 17.62 with a mean of 9.77 [mu]g/100 ml of plasma. Similar values for 20 milking, nonpregnant cows ranged from 2.14 to 8.40 with a mean of 4.58 [mu]g/100 ml of plasma. These experiments indicate that the method has considerable physiological significance in assessing adrenal cortical function in dairy cows.