Effect of egg-phosphatidylcholine on the chilling sensitivity and lipid phase transition of Asian elephant (Elephas maximus) spermatozoa

Publication Type:
 Journal Article
Year of Publication:
 2005
Authors:
 Joseph Saragusty, Thomas B. Hildebrandt, Yehudit Natan, Robert Hermes, Saar Yavin, Frank Goeritz, Amir Arav
Publication/Journal:
 Zoo Biology
Publisher:
 A Wiley Company, Inc., Wiley Subscription Services
Keywords:
 , , , ,
ISBN:
 1098-2361
Abstract:

Abstract 10.1002/zoo.20045.abs This study was conducted in an effort to improve our understanding of the response of Asian elephant (Elephas maximus, Em) spermatozoa to chilling. Semen was collected from two elephant bulls by means of the manual rectal stimulation method. Five out of seven semen collections were deemed to be suitable for use based on motility (ranging from 20% to 60%) and membrane integrity. We evaluated the chilling sensitivity by incubating the sperm with a fluorescent dye (5-carboxyfluorescein diacetate (cFDA)) at 16°C, 12°C, 4°C, and 22°C (control). Cells with an intact membrane retained the dye and were identified as viable. The membrane lipid phase transition (LPT) temperature curve was determined with a Fourier transform infrared (FTIR) spectrometer connected to an FTIR microscope. The LPT center, Tm, was determined by statistical analysis. The LPT and Tm were also assessed in fresh spermatozoa and spermatozoa incubated with egg yolk or egg-phosphatidylcholine (EPC) liposomes at 16°C, 12°C, 4°C, and 26°C (control). The results show that the membrane integrity of spermatozoa incubated at 16°C, 12°C, and 4°C decreased by 39%, 62%, and 67%, respectively, compared to the control. The LPT temperatures were between room temperature (26°C) and 10°C, with Tm at 14–16°C. The Tm for sperm incubated with liposomes or egg-yolk extender was below the measured range (2°C). Chilling sensitivity was found at a wide range of temperatures and transition temperatures, suggesting the presence of a wide variety of fatty acids (FAs) in the membrane with a high ratio of saturated-to-polyunsaturated FAs. Here we show that the protection afforded by the presence of egg yolk or liposomes in the extender is accomplished by shifting the Tm to below the 4°C point at which chilled semen is maintained for transport, or the point at which fast freezing begins to minimize cellular damage. Zoo Biol 0:1–13, 2005. © 2005 Wiley-Liss, Inc.

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