期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1990
卷号：87
期号：17
页码：6893-6896
DOI：10.1073/pnas.87.17.6893
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Mammalian sperm plasma membranes, in contrast to those of mammalian somatic cells, exhibit a significant fraction of lipid that does not diffuse laterally in the plane of the membrane. This nondiffusing fraction results from lipid-lipid interactions. Similar nondiffusing fractions are found in mixed-lipid model systems that contain coexistent gel and fluid domains. These results suggest that the sperm plasma membrane may also exhibit lateral phase segregations of lipids and may contain significant amounts of gel-phase lipid. In this paper we use differential scanning calorimetry to show that, in contrast to the plasma membranes of mammalian somatic cells, the plasma membrane from the anterior region of the head of ram sperm exhibits at least two major endothermic transitions, one centered at approximately 26 degrees C and one centered at approximately 60 degrees C. The heats of these transitions are consistent with gel-to-fluid transitions in model membranes. These transitions are observed both in plasma membrane vesicles and in rehydrated lipid extracts made from these vesicles. These results demonstrate that at physiological temperatures the lipids of the ram sperm plasma membrane are segregated into coexistent fluid and gel domains. Since sperm encounter a wide range of temperatures during their development, these phase transitions may be important in establishing dynamic domains of lipid requisite for epididymal storage and fertilization.
