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Effects of Storage Times and Temperatures on T₃, T₄, LH, Prolactin, Insulin, Cortisol and Progesterone Concentrations in Blood Samples from Cows¹

Cornell University³, Ithaca, NY 14853

Abstract

Little is known about stability of hormones in blood samples stored under various conditions. This study was conducted to examine stability of triiodothyronine (T₃), thyroxine (T₄), luteinizing hormone (LH), prolactin, insulin, Cortisol and progesterone in blood and serum samples. Experiment 1 was designed to determine if concentrations of these hormones were affected by exposure to cellular elements of anticoagulated and coagulated blood when stored at 4 C and room temperature (22 to 26 C). Jugular venous blood was collected from six diestrous Holstein cows into evacuated bottles containing sodium ethylenediaminetetraacetic acid (EDTA), heparin or no anticoagulant. Subsamples of EDTA-treated and heparinized blood were stored .25, .5, 1, 2, 4, 8, 24 and 72 h at 4 C or room temperature. Subsamples of blood without anticoagulant were stored in polypropylene tubes (clot tubes) or serum separator tubes for 1, 2, 4, 8, 24 and 72 h. Mean concentrations of T₃, T₄) LH, prolactin and Cortisol did not change in plasma or serum from either of the four types of samples stored at 4 C or room temperature for 72 h. The mean insulin concentration decreased 18% by 72 h in serum from serum separator tubes stored at room temperature. At 4 C, mean progesterone concentrations decreased 55% by 24 h and 73% by 72 h in plasma from EDTA-treated blood; 41% by 72 h in serum from clot tubes, and 26% by 24 h and 36% by 72 h in serum from serum separator tubes. At room temperature, progesterone concentrations decreased 35% by 4 h, 61% by 8 h, 92% by 24 h and 93% by 72 h in plasma from EDTA-treated blood; 49% by 4 h, 69% by 8 h, 91% by 24 h and 94% by 72 h in plasma from heparinized blood; 56% by 24 h and 83% by 72 h in serum from clot tubes, and 43% by 8 h, 60% by 24 h and 74% by 72 h in serum from serum separator tubes. In Exp. 2, we examined effects of storage times and temperatures on concentrations of the seven hormones in serum. Jugular venous blood from each of six diestrous Holstein cows was collected and allowed to clot for 3 h at 4 C. Subsamples of serum were stored 1 h (0 d) and 2,4, 6 and 8 d at -20 C, 4 C or room temperature. Concentrations of none of the hormones changed when serum was stored for 8 d at -20 or 4 C. Storage of serum at room temperature for 8 d did not affect concentrations of T3, T4, prolactin or LH. However, the mean progesterone concentration was reduced 18% by 8 d and the mean insulin concentration was reduced 62% by 4 d, but did not decrease further. Cortisol was reduced 12% by 2 d and remained at this level through 8 d. These data indicate that immunological activities of several hormones commonly measured in reproductive and metabolic endocrinology are very stable, whereas, others are quite unstable in blood samples. Stability of hormones and other substances in biological samples must be considered when estimating their concentrations by radioimmunoassay.

¹ Supported by a grant from the Alumni Assoc, of the New York State College of Veterinary Medicine.

² Address all correspondence to this author.

³ Diagnostic Endocrinol. Lab., New York State College of Vet. Med.