Summary. Bound sialic acids on rat spermatozoa were assayed by oxidation with 1 mMNaIO4 at 0\ s=deg\ C, liberating C-9 as formaldehyde which was further quantitated using 3 \ x = r e q -\ methyl-2-benzothiazolinone. The mean \ m=+-\ s.d. (n = 20) content of bound sialic acids of spermatozoa from the caput and cauda epididymidis was 50\m=.\9 \m=+-\ 8\m=.\0and 25\m=.\2 \m=+-\ 3\ m=. \ 8 nmol/108 spermatozoa respectively. About 85% of the former and 75% of the latter could be extracted by 1% Triton X-100 and 2 mM-dithiothreitol. About 70% of the former and 20% of the latter were released by neuraminidase from Vibrio cholerae. About 40% of the former and 30% of the latter were sensitive to trypsin. During sperm maturation, the decrease in the total bound sialic acids was due to the decrease in the neuraminidase-sensitive but not the neuraminidase-resistant sialic acids.

No abstract

Sialoglycoproteins of rat epididymal fluid and spermatozoa were radiolabelled by the NaIO4/KB3H4 method. At least 10 sialoglycoproteins of the epididymal fluids could be consistently demonstrated by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. Two major ones (Mr 21000 and 66000) were present in the fluids of the caput and cauda epididymidis. Two (Mr 28000 and 40000) were found only in the former and two (Mr 32000 and 42000) only in the latter. There were at least 11 sialoglycoproteins bound to the epididymal spermatozoa. During epididymal transport, 8 sialoglycoproteins on the spermatozoa decreased, one (Mr 48000) remained constant and one (Mr 31000) increased in amount. During sperm maturation, some sperm-bound sialoglycoproteins, especially 3 of small molecular weights, became more resistant to the treatments with neuraminidase, trypsin and Triton X-100.

Thermal immobilization was designed as a simple approach to study factors controlling sperm motility. Heating dissected epididymis or isolated epididymal sperm at 48°C to 52°C for 5 min abruptly and completely immobilized the sperm. The thermally immobilized sperm showed some alteration of membrane lipids, as indicated by the response of the surface ATPase to temperature change. However, no qualitative change in the surface negative charge was detectable by the binding of the cells to DEAE‐Sephadex beads. The immobilized cells can metabolize ATP into ADP and AMP similar to the control epididymal sperm. The ATP‐dependent sliding or disintegration of sperm flagella was completely prevented in the immobolized cells. The findings suggested that heat‐treatment disrupted the integrity of the sperm membrane and the motile apparatus, resulting in the loss of sperm motility. The development of post‐testicular antifertility agents should aim at interfering specifically with these components of the sperm.

Summary. Anionic