Validation of a homologous canine relaxin radioimmunoassay and application with pregnant and non-pregnant Northern fur seals (Callorhinus ursinus).
The primary objectives of this study were to validate a canine relaxin RIA for use in otariids and phocids and consider practical applications. For 6 captive Northern fur seal females, serum samples were grouped and examined according to pregnancy (n=13), post-partum (n=8) and non-pregnancy (n=6), and, for 2 captive Northern fur seal males, serum samples were grouped and examined together regardless of age (2 mo-15 yrs, n=6). Placental tissue was available for examination from one Northern fur seal, Steller sea lion and harbor seal. The validation process involved several steps using an acid-acetone extraction process to isolate a relaxin-containing fraction in pools of serum from each group of fur seals and placental tissue from each seal species. A relaxin-like substance was detected in extracts of pregnant, non-pregnant and male serum and placental tissue in a dose-responsive manner as increasing volumes of respective extracts or amounts of canine relaxin were introduced into the assay. In raw serum samples, mean immuno-reactive relaxin concentrations were higher (P<0.05) during pregnancy than post-partum and non-pregnancy, and lower (P<0.05) in male than female fur seals. During pregnancy, mean serum concentrations of relaxin progressively increased (P<0.05) over Months 4-10 and, in serial samples collected from the same fur seals before and after parturition, mean concentrations were higher (P<0.06) pre-partum than post-partum. In conclusion, validation of a homologous canine relaxin RIA for use in otariids and phocids resulted in the discovery of a relaxin-like substance in extracted and raw serum and placental tissue from Northern fur seals, a Steller sea lion and harbor seal. Distinctly higher immuno-reactive concentrations during pregnancy indicated the potential for relaxin to serve as a hormonal marker to differentiate between pregnant and non-pregnant or pseudopregnant pinnipeds.
Bergfelt
Don R
DR
US Environmental Protection Agency, Washington, DC 20460, USA. bergfelt.don@epa.gov
Steinetz
Bernard G
BG
Dunn
J Lawrence
JL
Atkinson
Shannon
S
Testa
J Ward
JW
Adams
Gregg P
GP
D000818:Animals; D004285:Dogs; D005260:Female; D046069:Fur Seals / Q000097:blood* / Q000378:metabolism; D008297:Male; D046049:Phoca; D011247:Pregnancy; D011258:Pregnancy Tests; D011863:Radioimmunoassay / Q000379:methods*; D012065:Relaxin / Q000097:blood*; D046070:Sea Lions
D012065:Relaxin