Investigation of an Immunoreactive Chorionic Gonadotropin-Like Substance in the Placenta, Serum, and Urine of Pregnant Bottlenose Dolphins (Tursiops truncatus)

Abstract: This study was designed to test the hypothesis that an immunoreactive chorionic gonadotropin (CG)-like substance is present in full-term dolphin placentas and to determine if CG immunoreactivity can be detected in corresponding serum and urine samples for potential application to diagnose pregnancy. Six placentas were collected immediately after parturition from four captive bottlenose dolphins in 2003, 2007 (Experiment 1), and 2011 (Experiment 2). Serum and urine were collected during early, middle, and late pregnancy from the same dolphins. In Experiment 1, an eCG radioimmunoassay (RIA) was used to analyze dilutions of supernatants from the homogenates of each placenta for eCG immunoreactivity, and a commercial hCG Enzyme-Linked Immunosorbent Assay (ELISA) was used to analyze individual serum samples and dilutions of pools of serum and urine for hCG immunoreactivity. Specific CG immunoreactivity was not detected above assay sensitivities in any of the supernatants of respective placental homogenates, including the highest concentrate (100 mg/mL), nor in any of the individual samples and pools of serum and urine. In Experiment 2, the highest placental homogenate was increased five-fold (500 mg/mL), sensitivity of the eCG RIA was increased six-fold, and a different combination of hCG antibodies was used in an alternative commercial “sandwich”-type ELISA. Despite the optimization, specific CG immunoreactivity in placental tissue and individual serum and urine samples was not detected above assay sensitivities. In conclusion, the hypothesis that an immunore-active CG-like substance is present in full-term dolphin placentas was not supported. In addition, non-immunoreactivity of a CG-like substance in serum and urine samples collected during various stages of pregnancy precluded the development and application of a CG-based immunoassay for diagnosing pregnancy status in dolphins.

Key Words: chorionic gonadotropin, placenta, immunoanalysis, pregnancy, bottlenose dolphin, Tursiops truncates

Document Type: Research article

DOI: 10.1578/AM.38.4.2012.354

Page Numbers: 354-361

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