http://xrm.phys.northwestern.edu/research/pdf_papers/2000/flesch_bba2000.pdf

Dynamics of the mammalian sperm plasma membrane in the process of fertilization.

Intact human sperm incorporated radiolabelled fatty acids into membrane phospholipids when incubated in medium containing bovine serum albumin as a fatty acid carrier. The polyunsaturated fatty acids were preferentially incorporated into the plasmalogen fraction of phospholipid. Uptake was linear with time over 2 hr; at this time sufficient label was available to determine the loss of fatty acids under conditions of spontaneous lipid peroxidation. Loss of the various phospholipid types, the loss of the various fatty acids from these phospholipids, and the overall loss of fatty acids were all first order. The loss of saturated fatty acids was slow with first order rate constant k1 = 0.003 hr-1; for the polyunsaturated fatty acids, arachidonic and docosahexaenoic acids, k1 = 0.145 and 0.162 hr-1, respectively. The rate of loss of fatty acids from the various phospholipid types was dependent on the type, with loss from phosphatidylethanolamine being the most rapid. Among the phospholipid types, phosphatidylethanolamine was lost at the greatest rate. Analysis of fatty acid loss through oxidation products was determined for radiolabelled arachidonic acid. Under conditions of spontaneous lipid peroxidation at 37 degrees C under air in the absence of albumin, free arachidonic acid was found in the medium, along with minor amounts of hydroxylated derivative. All the hydroperoxy fatty acid remained in the cells. In the presence of albumin, all the hydroperoxy fatty acid was found in the supernatant bound to albumin; none could be detected in the cells. Albumin is known as a very potent inhibitor of lipid peroxidation in sperm; its action may be explained, based on these results, as binding the damaging hydroperoxy fatty acids. These results also indicate that a phospholipase A2 may act in peroxidative defense by excising a hydroperoxy acyl group from phospholipid and providing the hydroperoxy fatty acid product as substrate to glutathione peroxidase. This formulation targets hydroperoxy fatty acid as a key intermediate in peroxidative degradation.

Differential incorporation of fatty acids into and peroxidative loss of fatty acids from phospholipids of human spermatozoa

Testicular sperm that have undergone spermatogeneis and spermiogenesis appear mature from a morphological standpoint but have acquired neither progressive motility nor the ability to fertilize a metaphase Il-arrested egg. In many species, progressive motility and fertilization competence are acquired during epididyma! transit, but complete fertilization capacity in vivo is only gained upon residence in the female reproductive tract for a finite period of time. The molecular and physiological events that confer on the sperm the ability to feftilize during residence in the female tract are collectively known as pacitation.” These maturational events can also be accomplished in vitro in defined media, the composition of which approximates the environment of the female reproductive tract. Although capacitation was discovered independently by Austin (1951, 1952) and Chang (1951, 1955) nearly one-half century ago, little is known to date about the molecular basis of this important event. This brief review will consider some of the recent findings made toward an understanding of capacitation using in vitro models. The purpose of this review is not to provide an exhaustive analysis of capacitation but is to offer an

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.1939-4640.1998.tb01994.x

The molecular basis of sperm capacitation.

An adhesion-associated agonist from the zona pellucida activates G protein-promoted elevations of internal Ca2+ and pH that mediate mammalian sperm acrosomal exocytosis.

https://escholarship.org/content/qt8f67899s/qt8f67899s.pdf?t=ovhxkb

Neil Wummer

Papers

Capacitation and acrosome reactions in human spermatozoa monitored by a chlortetracycline fluorescence assay