title: Effect of temperature on the fluidity of boar sperm membranes.
abstract: Fluidity was used to assess changes in molecular organization of boar spermatozoa plasma membranes from (1) the head and (2) the rest of the sperm body and acrosome as a consequence of temperature. The initial fluidity of the head membranes at 25 degrees C was less than that of the sperm body membranes (P less than 0.05). When held at 25 degrees C, the fluidity of the head membranes decreased for 105 +/- 8 min and then stabilized for the remainder of the 160-min incubation. Calcium (10 mM) caused a significantly greater decrease in fluidity. The fluidity of the sperm body membranes increased slightly over time in the absence of Ca2+, but decreased significantly with Ca2+. Cooling from 25 to 5 degrees C and subsequent heating to 40 degrees C (0.4 degrees C/min) caused marked alterations in the fluidity of each membrane. Cooling the head membranes prevented the fluidity increase seen at 25 degrees C, while reheating caused a dramatic decrease in fluidity. Fluidity of the head membranes was now unaffected by Ca2+. Lipid phase transitions, indicated by sharp break points in data curves, were detected at the onset of reheating (7 +/- 3 C) and at 23 +/- 4 degrees C during reheating. Fluidity of the sperm body membranes decreased slightly and in a linear fashion with Ca2+. Without Ca2+, the sperm body membranes showed an additional lipid phase shift at 31 +/- 5 degrees C, which led to a rapid fall in fluidity. These results suggest that the fluidity, and therefore the molecular structure, of sperm head and body membranes differ.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Animal Science, University of Manitoba, Winnipeg, Canada.
authors.forename: A T
authors.initials: AT
authors.lastname: Canvin
authors.forename: M M
authors.initials: MM
authors.lastname: Buhr
mesh_terms: D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects; D013077:Sperm Head / Q000648:ultrastructure; D013094:Spermatozoa / Q000648:ultrastructure*; D013552:Swine / Q000502:physiology*; D013696:Temperature
chemical_list: D002122:Calcium Chloride