Effects of season and sample handling on measurement of plasma alpha-melanocyte-stimulating hormone concentrations in horses and ponies.
OBJECTIVE
To investigate effects of sample handling, storage, and collection time and season on plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentration in healthy equids.


METHODS
11 healthy Standardbreds and 13 healthy semiferal ponies.


METHODS
Plasma alpha-MSH concentration was measured by use of radioimmunoassay. Effects of delayed processing were accessed by comparing alpha-MSH concentrations in plasma immediately separated with that of plasma obtained from blood samples that were stored at 4 degrees C for 8 or 48 hours before plasma was separated. Effects of suboptimal handling were accessed by comparing alpha-MSH concentrations in plasma immediately stored at -80 degrees C with plasma that was stored at 25 degrees C for 24 hours, 4 degrees C for 48 hours or 7 days, and -20 degrees C for 30 days prior to freezing at -80 degrees C. Plasma alpha-MSH concentrations were compared among blood samples collected at 8:00 AM, 12 noon, and 4:00 PM. Plasma alpha-MSH concentrations were compared among blood samples collected in January, March, April, June, September, and November from horses and in September and May from ponies.


RESULTS
Storage of blood samples at 4 degrees C for 48 hours before plasma was separated and storage of plasma samples at 4 degrees C for 7 days prior to freezing at -80 degrees C resulted in significant decreases in plasma alpha-MSH concentrations. A significantly greater plasma alpha-MSH concentration was found in September in ponies (11-fold) and horses (2-fold), compared with plasma alpha-MSH concentrations in spring.


CONCLUSIONS
Handling and storage conditions minimally affected plasma alpha-MSH concentrations. Seasonal variation in plasma alpha-MSH concentrations must be considered when evaluating pituitary pars intermedia dysfunction in equids.
McFarlane
Dianne
D
Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada C1A 4P3.
Donaldson
Mark T
MT
McDonnell
Sue M
SM
Cribb
Alastair E
AE
D000704:Analysis of Variance; D000818:Animals; D006736:Horses / Q000097:blood*; D011863:Radioimmunoassay; D012621:Seasons; D013048:Specimen Handling; D013997:Time Factors; D000521:alpha-MSH / Q000097:blood*
D000521:alpha-MSH