ISSN:
0148-7280
Keywords:
fertilization
;
proteolysis
;
nuclear proteins
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
Spermatogenesis in the male rat involves chemical and physical transformation of chromatin. There is a shift in the chemical composition of rat testicular sperm chromatin containing histones to nucleoprotamines in the mature sperm. Rat protamine contains a high percentage of arginine. The biosynthesis and kinetics of H3-arginine incorporation into rat sperm protamine was at its peak in the testis 2 days after intratesticular injection. The specific activity of protamine in the testis was reduced to 50% 5 days after injection. Specific activity of protamine in the epididymis was maximal at 9 days after injection and remained at a similar level for 12 days. The kinetics of H3-arginine and H3-thymidine in ejaculated sperm were compared. It was found that maximal specific activity of H3-arginine (H3-Arg/No. of sperm) in the spermatozoa was obtained 20-22 days following its intratesticular injection. The peak of H3-thymidine specific activity (H3-thymidine/No. of sperm) was obtained 53-59 days following the injection.H3-Arg labeled sperm were capacitated in vitro and were allowed to penetrate zona free rat eggs in vitro. The disappearance of the label from the sperm head was observed 1-2 hr after penetration. Protamine labeled in vitro with I125 incubated with extracts of freshly ovulated rat eggs shows that protamine could be degraded by the cytoplasmic extract (10-30%). The proteolytic activity is maximal at pH 7.0-8.0. Cytoplasmic extracts from cumulus cells incubated with I125 rat protamine under identical conditions did not show any significant proteolytic activity. Trypsin degradation of rat protamine shows a different pattern of degradation. It is assumed that the H3-labeled protamine in the sperm chromatin is removed and probably degraded early after penetration, making possible the remodeling of the sperm chromatin by embryonic histones.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrd.1120140403
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